Next Article in Journal
Agricultural Land-Use Increases Floral Species Richness in Tropical Dry Forest and Savannah Ecosystems in West Africa
Next Article in Special Issue
The Enigmatic Avian Oogenus Psammornis: A Review of Stratigraphic Evidence
Previous Article in Journal
Phylogeography and Genetic Structure of Sand Dune Specialist Stilpnolepis centiflora (Asteraceae) in Northwest China Revealed by Molecular Data
Previous Article in Special Issue
Contrasting Patterns of Sensory Adaptation in Living and Extinct Flightless Birds
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:

The Evolution and Fossil Record of Palaeognathous Birds (Neornithes: Palaeognathae)

Department of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, UK
Museum of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
Authors to whom correspondence should be addressed.
Diversity 2022, 14(2), 105;
Submission received: 31 December 2021 / Revised: 24 January 2022 / Accepted: 27 January 2022 / Published: 1 February 2022
(This article belongs to the Special Issue Evolution and Palaeobiology of Flightless Birds)


The extant diversity of the avian clade Palaeognathae is composed of the iconic flightless ratites (ostriches, rheas, kiwi, emus, and cassowaries), and the volant tinamous of Central and South America. Palaeognaths were once considered a classic illustration of diversification driven by Gondwanan vicariance, but this paradigm has been rejected in light of molecular phylogenetic and divergence time results from the last two decades that indicate that palaeognaths underwent multiple relatively recent transitions to flightlessness and large body size, reinvigorating research into their evolutionary origins and historical biogeography. This revised perspective on palaeognath macroevolution has highlighted lingering gaps in our understanding of how, when, and where extant palaeognath diversity arose. Towards resolving those questions, we aim to comprehensively review the known fossil record of palaeognath skeletal remains, and to summarize the current state of knowledge of their evolutionary history. Total clade palaeognaths appear to be one of a small handful of crown bird lineages that crossed the Cretaceous-Paleogene (K-Pg) boundary, but gaps in their Paleogene fossil record and a lack of Cretaceous fossils preclude a detailed understanding of their multiple transitions to flightlessness and large body size, and recognizable members of extant subclades generally do not appear until the Neogene. Despite these knowledge gaps, we combine what is known from the fossil record of palaeognaths with plausible divergence time estimates, suggesting a relatively rapid pace of diversification and phenotypic evolution in the early Cenozoic. In line with some recent authors, we surmise that the most recent common ancestor of palaeognaths was likely a relatively small-bodied, ground-feeding bird, features that may have facilitated total-clade palaeognath survivorship through the K-Pg mass extinction, and which may bear on the ecological habits of the ancestral crown bird.

1. Introduction

Crown birds (Neornithes) comprise roughly 11,000 extant species [1]. They are divided into the reciprocally monophyletic Palaeognathae and Neognathae, with the latter including the hyperdiverse clade Neoaves [1]. At no point in time do total group palaeognaths appear to have been particularly diverse, especially in comparison with contemporaneous neognath diversity. Despite their relatively sparse taxonomic diversity, however, the position of palaeognaths as the sister group to all other neornithines makes them critical to efforts to understand the early evolutionary history of crown birds. Palaeognathae is diagnosed by several traits including a unique palatal structure characterized by enlarged basipterygoid processes and fused pterygoids and palatines (Figure 1), a grooved rhamphotheca, a single articular facet for the otic capitulum of the quadrate, and open ilioischiadic foramina (Figure 2) [2,3,4,5,6]. The palatal structure of palaeognaths was traditionally considered plesiomorphic for Neornithes [7], though recent evidence regarding the palatal structure of the near-crown Ichthyornithes may indicate that the palaeognathous palate is in fact a synapomorphy of Palaeognathae [8,9].
Extant palaeognaths are represented by 46 species of tinamou (Tinamidae) and two species of rhea (Rheidae) in Central and South America, two species of ostrich (Struthionidae) in Africa, the monotypic emu and three species of cassowaries (Casuariidae) in Australia and New Guinea, and approximately five species of kiwi in New Zealand (Apterygidae) [10]. Nine species of moa (Dinornithiformes) [11] and four species of elephant bird (Aepyornithidae) [12] survived into the Holocene in New Zealand and Madagascar respectively, before their extinction which may have been related to human activity that had a disproportionate impact on insular flightless birds [13].
Despite being relatively species-poor, extant and recently extinct palaeognaths encompass an impressive range of body sizes and ecologies. The group contains both cursorial open habitat specialists (e.g., emu) and graviportal forest dwellers (e.g., cassowaries), and feeding strategies ranging from cryptic nocturnal invertivores (e.g., kiwi) to megaherbivorous browsers (e.g., moa). Out of all extant palaeognaths, only tinamous (Tinamidae) are capable of flight [14]. This clade comprises small to medium-sized birds, ranging from 43 g in the smallest species (the Dwarf Tinamou Taoniscus nanus) [15], to 2080 g in the largest females of the Gray Tinamou (Tinamus tao) [16]. By contrast, flightless palaeognaths, from here on referred to collectively as “ratites” (acknowledging the paraphyletic nature of the group), are renowned for their gigantism. The Common Ostrich Struthio camelus is the world’s largest extant bird in both height and weight, with large males reaching sizes up to 2.8 m and 156 kg [17]. Recently extinct ratites were even larger: A body mass of 860 kg was estimated from femur measurements of an exceptionally large individual of the elephant bird Vorombe titan, making this species the heaviest-known bird ever discovered [12]. Females of the moa Dinornis robustus were less massive but appear to have constituted the tallest birds yet discovered, attaining heights of 3.6 m [18,19].
Several early authors argued that ‘ratites’ represented a non-monophyletic assemblage of large-bodied, flightless birds, and debate regarding the potential non-monophyly of ratites persisted through much of the 20th Century [4,20,21,22,23,24]. Opinion shifted with the widespread acceptance of continental drift theory in the latter half of the 20th century, as a monophyletic “Ratitae” became enshrined as a classic example of Gondwanan vicariance biogeography, a hypothesis stipulating that stem group ratites became flightless prior to the breakup of Gondwana, and that Gondwanan fragmentation drove the divergence of the extant ratite lineages as populations became geographically isolated from one-another [25,26,27]. This hypothesis of a monophyletic “Ratitae”, sister to Tinamidae, was supported by a number of phenotypic features such as the absence of a triosseal canal and sternal keel, and the presence of a fused scapulocoracoid (Figure 3) [5]. Indeed, the term “ratite” refers to the flat, raft-like sterna of taxa lacking a sternal keel (Figure 4) [28]. This consensus opinion was upheld for several decades by most phylogenetic analyses of morphological characters [29,30,31], though analyses of cranial characters recovered alternative relationships [32,33,34]. However, over the past twenty years, molecular phylogenetic analyses have forced a wholescale revision of the Gondwanan vicariance paradigm of palaeognath evolution and historical biogeography. Evidence from analyses of both nuclear [35,36,37,38,39,40,41,42,43] and mitochondrial DNA [41,42,44,45,46], as well as large-scale phylogenomic analyses [47,48,49,50], demonstrate that tinamids are in fact phylogenetically nested within ratites, rendering “Ratitae” paraphyletic, once again reviving the early hypothesis of ratite non-monophyly [4,20,21,22,23,24] (Figure 5).
The most parsimonious interpretation of this revised tree topology would be that the most recent common ancestor of crown Palaeognathae was flightless, with a reacquisition of flight arising along the tinamou stem lineage. This interpretation is indeed favoured by maximum likelihood analyses [44] and cannot be definitively rejected; however, this hypothesis would seem to be unlikely from first principles (after all, strong evidence exists for only four independent acquisitions of powered flight throughout the entire evolutionary history of animals [51]). By contrast, multiple independent transitions to flightlessness within the same crown bird subclade are not uncommon. For example, flightlessness has arisen dozens of times in Rallidae among island-dwelling taxa [52,53]. According to some recent molecular topologies, transitions to flightlessness arose a minimum of six times in palaeognaths, and transitions to gigantism a minimum of five [41,45].
The recent revival of a phylogenetic hypothesis stipulating that ratites repeatedly and independently lost the capacity to fly has largely been driven by molecular phylogenetic analyses [36,37,38,39,40,41,42,43,44,45,46,48,49,50,54,55,56,57,58], but has accrued supporting evidence from independent datasets. For instance, embryological studies have demonstrated important differences in patterns of wing growth among ostriches and emu, suggesting that alternative heterochronic mechanisms may underlie the acquisition of flightlessness in disparate ratite taxa and potentially supporting independent evolutionary transitions to flightlessness among ratites [59]. Furthermore, misexpression of the cardiac transcription factor Nkx2.5 is associated with reduced wing growth in chicken embryos, and this transcription factor is expressed in the wings of emu embryos but not ostriches—again indicating the potential non-homology of flightlessness in emu and ostriches [60]. Sackton, et al. [50] found that many similarities in ratite forelimb morphology may be the result of convergence in gene regulatory networks, rather than the product of homologous changes to protein coding genes. Overall, the existing body of evidence is congruent with the hypothesis that ‘ratites’ are indeed paraphyletic, and have repeatedly converged on a suite of remarkably similar morphologies that were long interpreted as synapomorphies for the group. Much remains to be understood about the underlying drivers of these independent transitions to large size and flightlessness, as well as the developmental underpinnings of convergent ratite morphologies.
The recognition of ratite paraphyly, coupled with phylogenomic time trees that indicate an origin of crown palaeognaths long after the breakup of Gondwana commenced (e.g., [41,42,45,48,49,55]), makes the classic vicariance hypothesis untenable. Instead, present-day palaeognath biogeography must be the product of dispersal of volant ancestral palaeognaths to multiple landmasses preceding independent origins of flightlessness (Figure 6). However, this interpretation raises many questions regarding the nature of the volant last common ancestor of crown palaeognaths. Tinamous are the only extant volant palaeognaths available for reference, but they are primarily ground-dwelling and are only capable of flight over relatively short distances to flee predators or roost in trees [14,61]. It is difficult to imagine a burst-flying tinamou-like bird undertaking the transoceanic journeys needed to explain the distribution of extant palaeognaths (Figure 6), thus they would appear to be a poor analogue for hypothetical dispersive ancestral palaeognaths. Fossil evidence further suggests that the specialized burst flying of extant tinamous was not plesiomorphic for palaeognaths. The extinct lithornithids (Lithornithidae), known from the Paleocene and Eocene of Europe and North America, were apparently volant and appear to represent the oldest and most stemward known total-clade palaeognaths [49,62,63,64,65]. Importantly, they also appear to have been more capable long-distance fliers than extant tinamids are [62,65], and, as the earliest known palaeognaths in the fossil record, they may provide the best models for informing reconstructions of the dispersive ancestral palaeognaths that gave rise to extant palaeognath diversity.
In order to probe deeper into the origin and early evolution of total group Palaeognathae, an in-depth understanding of the palaeognath fossil record is necessary. Early fossil palaeognaths are rare, and the phylogenetic interrelationships among them are poorly understood. For example, the monophyly and phylogenetic position of lithornithids are debated, and thus their relevance for clarifying the pattern and timing of the extant palaeognath radiation remains unclear. Due to the phylogenetic position of palaeognaths as the extant sister taxon of all other Neornithes, stem palaeognaths, which may include lithornithids, should provide key insight into the nature of the ancestral crown bird. Recent time-scaled phylogenies suggest that total-group palaeognaths were one of just a small number of extant neornithine lineages that passed through the Cretaceous-Paleogene (K-Pg) mass extinction event (e.g., [48,69,70,71,72]). A better understanding of the ecology and biology of early stem palaeognaths could therefore help clarify the biological attributes of avian survivors of the end-Cretaceous mass extinction, which appears to have eliminated all non-neornithine avialans [73]. Early palaeognath fossils from around the world will also be critical for illustrating how the remarkable convergent evolution of flightlessness and gigantism arose among crown palaeognaths, as well as providing insight into the biogeographic origins of extant palaeognath subclades and their responses to Cenozoic shifts in climate and environment [74,75].
Here, we summarize the current state of knowledge regarding the palaeognath fossil record. Useful reviews on palaeognath fossils and the evolutionary history of this group have previously been published, e.g., [76,77,78], and we refer interested readers to these excellent summaries, but the present review is the first attempt to systematically address the fossil record of palaeognaths in its entirety. We present the most specific locality data reported in the literature for each fossil occurrence, necessarily limited by the differential specificity available for certain records. We outline key lingering gaps in the known palaeognath fossil record, and suggest potential ways forward in hopes of narrowing those gaps. In addition, we provide an overview of strong inferences about palaeognath macroevolution that can be made on the basis of current molecular phylogenies and estimated divergence times, and summarise what can be reasonably inferred about the most recent common ancestor of crown group palaeognaths. We hope that this review provides both a solid base of information for those interested in the evolution and fossil record of palaeognaths, and helps inspire further work clarifying the evolutionary history of these remarkable birds.
Institutional abbreviations are as follows: AM—Australian Museum, Darlinghurst, Australia; AIM—Auckland Institute and Museum, Auckland, New Zealand; AMNH—American Museum of Natural History, New York, New York, USA; AU—Auckland University, Auckland, New Zealand; AUG—Aristotle University School of Geology, Thessaloniki, Greece; BGR—Bundesanstalt für Geowissenschaften Und Rohstoffe, Hanover, Germany; CICYTTP—Centro de Investigación Científica y de Transferencia Tecnológica a la Producción, Diamante, Argentina; CPC—Commonwealth Palaeontological Collections, Canberra, Australia; DK—Danekrae collections, Geological Museum, University of Copenhagen, Copenhagen, Denmark; FMNH—Field Museum of Natural History, Chicago, Illinois, USA; GHUNLP—Universidad Nacional de La Pampa, Santa Rosa, Argentina; GMB—Geological Museum of Budapest, Budapest, Hungary; GMH—Geiseltalmuseum, Martin Luther University, Halle, Germany; HLMD—Hessisches Landesmuseum, Darmstadt, Germany; IGM—Institute of Geology, Mongolian Academy of Sciences, Ulaan Baatar, Mongolia; IRSNB—Institut royal des Sciences naturelles de Belgique, Brussels, Belgium; IVPP—Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, People’s Republic of China; KNM—Kenya National Museum, Nairobi, Kenya; MACN—Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Buenos Aires, Argentina; MASP—Colección del Museo de Ciencias Naturales y Antropológicas, Paraná, Argentina; MFN—Museum für Naturkunde, Berlin, Germany; MGL—Geological Museum of Lausanne, Lausanne, Switzerland; MGUH—palaeontology type collection, Geological Museum, University of Copenhagen, Copenhagen, Denmark; MHNT—Muséum de Toulouse, Toulouse, France; MLP—Museo de La Plata, La Plata, Argentina; MNHN—Muséum National d’Histoire Naturelle, Paris, France; MPCN—Museo Patagónico de Ciencias Naturales, General Roca, Argentina; MPM—Museo Regional Provincal Padre Manuel Jesús Molina, Río Gallegos, Argentina; MUFYCA—Museo Florentino y Carlos Ameghino (Instituto de Fisiografía y Geología), Rosario, Argentina; MV—Musée Vivenel, Compiègne, France; NHMUK—Natural History Museum, London, UK; NJSM—New Jersey State Museum, Trenton, New Jersey, USA; NMNHS—National Museum of Natural History, Bulgarian Academy of Sciences, Sofia, Bulgaria; NMNZ—Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand; NNPM—National Museum of Natural History of the National Academy of Sciences, Kyiv, Ukraine; ONU—Odes’kiy Natsional’niy Universitet, Odessa, Ukraine; PIN—Palaeontological Institute, Russian Academy of Sciences, Moscow, Russian Federation; PU—Princeton University Collection (now at Yale Peabody Museum), Princeton, New Jersey, USA; QM—Queensland Museum, Brisbane, Australia; RAM—Raymond Alf Museum, Claremont, California, USA; ROM—Royal Ontario Museum, Toronto, Ontario, Canada; SAM—South Australian Museum, Adelaide, Australia; SGPIMH—Geologisch-Paläontologisches Institut und Museum der Universität Hamburg, Hamburg, Germany; UCMP—University of California Museum of Paleontology, Berkeley, California, USA; UCR—University of California Riverside, Riverside, California, USA; UM—Museum of Paleontology, University of Michigan, Ann Arbor, Michigan, USA; UNSW—University of New South Wales; Sydney, Australia; USNM—Smithsonian Museum of Natural History, Washington, DC, USA; WN—Michael C.S. Daniels collection, Essex, UK; YPM—Yale Peabody Museum, New Haven, Connecticut, USA; ZIUU—Zoologiska Museum, Uppsala Universitet, Sweden.

2. Overview of the Palaeognath Fossil Record

2.1. Lithornithidae

Lithornithids were small bodied, presumably volant birds that were first recognized as palaeognaths by Houde and Olson [79], and described in detail as a clade by Houde [62]. Thus far, they are only known from Europe and North America, contrasting with the Gondwanan distribution of extant palaeognaths. At first glance, they appear remarkably similar to tinamous, particularly in the shape of the skull. Fossil eggshells attributed to lithornithids are also very reminiscent of those of tinamous, and it has been hypothesized that lithornithids shared the same polygynandrous breeding behaviour of many extant palaeognaths [62]. However, numerous characters distinguish tinamous and lithornithids, which are detailed by Houde [62]. On the basis of a more distally positioned deltopectoral crest, longer and more curved humeral shaft, and a less distally elongated sternum in lithornithids compared with tinamous, Houde [62] also speculated that lithornithids were much more capable long-distance fliers than extant tinamous are. This idea received further support from a reconstruction of the wing of a specimen of the Eocene lithornithid Calciavis grandei with preserved carbonized feather traces, which indicated that this species may have been capable of long-distance flapping flight [65].
Since their fossils are most often recovered from nearshore lacustrine or marine environments, it was suggested that lithornithids may have exhibited a shorebird-like ecology [62], though this may be coincidental as these depositional settings are most likely to produce fossils in general. The lithornithid jaw apparatus appears well suited to distal rhynchokinesis, which allows a bird to capture food items in the ground without having to fully open the jaws [62]. This suggests they could have used their bills for probing the substrate for food items, in a manner more similar to kiwi than tinamous [62]. Additional evidence for this type of foraging behaviour comes from the recognition of mechanoreceptors known as Herbst corpuscles in the rostrum of lithornithids [80], which form a tactile bill-tip organ that picks up mechanical vibrations to detect buried prey.
A major unresolved question is whether Lithornithidae predate the K-Pg mass extinction. The cranial end of a right scapula with a distinctive pointed acromion was recovered from the latest Maastrichtian or earliest Danian Hornerstown Formation in New Jersey, USA [63]. If this material indeed belongs to a lithornithid, it would provide compelling evidence that the clade survived across the boundary. However, it should be noted that several Mesozoic stem ornithurines also have a hooked acromion that approaches the condition seen in Lithornithidae [64,81,82]. Thus, the identity of this fossil remains uncertain, and more material needs to be recovered from both this formation and other contemporaneous localities to clarify which groups of total-clade palaeognaths persisted across the K-Pg boundary.

2.1.1. North American Lithornithids

Definitive lithornithid fossils are known from North America from the middle Paleocene to the early Eocene (Figure 7, Table 1) [62,83,84,85,86,87,88]. The earliest uncontroversial record on this continent is Lithornis celetius, from the middle Paleocene (early to middle Selandian) Fort Union Formation of Montana and the Polecat Bench Formation of Wyoming [62]. The entire skeleton of this species is known from a composite series of individuals [62]. Slightly younger than L. celetius is a proximal end of a humerus from the middle Paleocene (Tiffanian) Goler Formation in southern California. Despite being fragmentary, its large, dorsally positioned humeral head and subcircular opening to the pneumotricipital fossa diagnose it as a probable lithornithid, and it was assigned to the genus Lithornis [88]. As nearly all North American lithornithids derive from the Rocky Mountain region, this fossil extends their known range significantly further west.
Two sympatric species are known from the late Paleocene (late Thanetian) Sand Coulee Beds of the Willwood Formation in Wyoming. Lithornis promiscuus was the larger of the two, and is the largest species in its genus [62]. Like L. celetius, virtually all bones of the skeleton are known from a composite series [62]. The holotype, USNM 336535, preserves the entire forelimb skeleton. The smaller Lithornis plebius is known from all major appendicular elements [62]. Houde [62] acknowledged the possibility that L. promiscuus and L. plebius may belong to a single sexually dimorphic species, but erred on the side of a more conservative species diagnosis and retained them as separate taxa. Houde [62] tentatively referred specimen NHMUK A 5303 from the London Clay on the Isle of Sheppey, UK to the latter species. Owing to both the homogeneity of the global hothouse climate and the shorter distance across the North Atlantic at the time, North American and European avifaunas were remarkably similar during the late Paleocene and early Eocene (e.g., [76,113,114]). Finding the same species on both sides of the Atlantic should therefore not come as a surprise, and if NHMUK A 5303 is indeed an example of L. plebius it would hint towards the dispersal capabilities of these birds.
The remaining North American lithornithids are Eocene in age. Paracathartes howardae [115] was found in early Eocene strata of the Willwood Formation [62]. With the exception of the sternum and pelvis, all bones of this species are again known from a composite series [62]. The lacustrine Green River Formation deposited by the Gosiute, Uinta, and Fossil palaeolakes in what is now Utah, Wyoming, and Colorado has yielded an enormous wealth of fossils, most often preserved as slabs [116]. The Fossil Butte member of the formation, deposited by the short-lived early Eocene Fossil Lake [116], has produced the greatest number of lithornithid specimens thus far [64], as well as a great wealth of other bird fossils (e.g., [117,118,119,120,121,122,123,124,125,126,127,128]). A minimum of two lithornithid species have been found in this Lagerstätte [64]. The holotype of Pseudocrypturus cercanaxius [62] is a complete skull and mandible, with nine cervical vertebrae in articulation [62]. A spectacular crushed articulated specimen missing only the pelvis and caudal vertebrae is owned privately by Siber and Siber, and a cast of this specimen is in the collections of the USNM. Two skeletons collected from the London Clay in England were provisionally referred to this species [62], making it another lithornithid with a possible transatlantic distribution. The recently named Calciavis grandei [64] was described from a complete, mediolaterally compressed skeleton with preserved soft tissue including feathers, pedal scales, and claw sheaths. A referred specimen includes most of the postcranial skeleton minus the femora and pelvic region, and a disarticulated skull [64].

2.1.2. European Lithornithids

The fossil record of lithornithids in Europe also begins in the middle Paleocene, and stretches to the middle Eocene (Figure 7, Table 1) [96,111,112]. The Orp Sand member (early to middle Selandian) of the Heers Formation in Maret, Belgium yielded a distal humerus fragment and a partial carpometacarpus that were assigned to Lithornithidae, but the fossils are too incomplete to be assigned at a generic level [96]. The next oldest European lithornithid, Fissuravis weigelti, is also known from fragmentary remains, in this case the omal end of an isolated coracoid from the late middle Paleocene (Selandian) of the fissure filling of Walbeck, Germany [98]. A lack of clear diagnostic features has cast some level of doubt to this assignment. The coracoid lacks any lithornithid character other than similarity in size, and seems to be missing the small foramina on the posteroventral surface of the hooked acrocoracoid process that is an apomorphy of this clade [64]. Regardless of the true affinities of Fissuravis weigelti, the Maret fossils demonstrate that Lithornithidae stretch at least as far back in time in Europe as they do in North America.
As noted by Houde, one of the first fossil birds known to science was Lithornis vulturinus [62,129], the holotype specimen of which was purchased by the Royal College of Surgeons in 1798. The holotype was sadly destroyed in the Second World War, though detailed woodcut drawings of the holotype [130] allowed for the identification of a neotype by Houde [62]. The neotype, from the early Eocene (Ypresian) London Clay, was originally identified as an early relative of turacos and named Promusophaga magnifica by Harrison and Walker [131]. It consists of a right humerus, radius, ulna, and carpometacarpus, all missing the distal ends, a right scapula, partial sternum, distal left radius and ulna, proximal left femur, proximal right tibiotarsus, a vertebral series, and ribs within a clay nodule [62]. A large amount of fragmentary material from the London Clay, mainly hindlimb elements, has been referred to this species [102]. A slightly younger specimen from the early Eocene Fur Formation of Denmark preserves a three-dimensional skull in articulation with a nearly complete postcranial skeleton and has been described in great detail [102,104]. Another Danish fossil, a distal left humerus from the latest Paleocene-earliest Eocene Olst Formation, was also referred to this taxon [102].
Lithornis nasi [132], also from the early Eocene London Clay Formation, was considered a junior synonym of L. vulturinus by Bourdon and Lindow [102]. As the material comes from the type locality of L. vulturinus, these authors interpreted the differences between L. nasi and L. vulturinus as intraspecific variation. The holotype consists of proximal fragments of a left humerus and right ulna, distal fragments of a right femur and a right tibiotarsus, and two thoracic vertebrae [62]. Houde [62] tentatively assigned two specimens from Early Eocene Willwood Formation to L. nasi. Another bird from the London Clay, ?Lithornis hookeri [132], was tentatively referred to the genus by Houde [62]. The holotype, a distal end of a tibiotarsus, suggests it was smaller than all currently known lithornithids [62]. The Messel lithornithid from the middle Eocene of Germany (47–48 MYA) is the youngest lithornithid material yet discovered [111,112]. Known from a partial postcranial skeleton and a skull that appear to represent the same species, it was assigned to the genus Lithornis but not to a species-level taxon [112].

2.1.3. Systematics of Lithornithidae

While it is generally accepted that lithornithids are indeed total-clade palaeognaths, important questions regarding their systematics remain: Do lithornithids represent a monophyletic radiation of volant stem or crown palaeognaths? Do they represent a paraphyletic grade of stem palaeognaths? Or, are they polyphyletic, with some taxa more closely related to certain extant palaeognath lineages than others (Figure 8)? All three scenarios would seem to be possible considering that the earliest members of several extant palaeognath subclades would most likely have been relatively small and volant. Houde [62] argued that lithornithids are not monophyletic and placed Paracathartes closer to other ratites on the basis of similar histological growth patterns, and the reduced, rounded postorbital process of its frontals. More recent authors have speculated that this histological similarity exists because Paracathartes is larger than other lithornithids, reaching approximately the size of a turkey [76].
The phylogenetic analyses of both Nesbitt and Clarke [64] and Yonezawa, et al. [49] recovered lithornithids as a monophyletic group. The character matrix used by Nesbitt and Clarke [64] contained 182 characters combined from the morphological datasets of Cracraft [5], Bledsoe [133], Lee, et al. [29], Mayr and Clarke [134], Clarke [81], Clarke, et al. [135], and new observations gathered by the authors for 38 terminal taxa. In their unconstrained analyses, Lithornithidae was recovered as the sister taxon to Tinamidae at the base of Palaeognathae, congruent with previous morphological phylogenetic hypotheses. This is unsurprising, given that lithornithids and tinamids share numerous skeletal similarities that often optimize as synapomorphies of a lithornithid + tinamou clade. When Paracathartes was constrained as sister to ratites, the resultant nonmonophyly of Lithornithidae added a significant number of steps to the analysis. The only character that supported this relationship was the reduction of the postorbital process of the frontal, which the authors considered to be convergent. When relationships of living palaeognaths were constrained to match those recovered by molecular phylogenies, lithornithids were recovered as a clade of stem group palaeognaths. Though Nesbitt and Clarke [64] were unable to achieve any resolution within Lithornithidae, lithornithid monophyly received relatively high support. However, the authors acknowledge the need for future analyses assimilating additional lithornithid character sets to further test the monophyly and phylogenetic position of lithornithids.
A strict consensus tree using parsimony constrained to match recent molecular phylogenetic topologies recovered a monophyletic Lithornithidae sister to Tinamidae, but when the molecular constraint was removed and replaced with constraints enforcing sister group relationships between Palaeognathae + Neognathae and Neoaves + Galloanserae, Lithornithidae instead resolved sister to a Dinornis + Dromaius + Struthio clade to the exclusion of tinamous [136]. In an analysis of this same dataset with new characters added and increased taxon sampling, Bayesian analysis placed lithornithids as stem palaeognaths, and a maximum parsimony analysis of this dataset with cranial characters weighted more strongly found strong support for a monophyletic Lithornithidae in this same position [137]. When characters were unweighted in the maximum parsimony analysis but constrained to a molecular backbone, a monophyletic Lithornithidae was once again sister to Tinamidae [137]. Almeida, et al. [42] also recovered lithornithids as sister to crown Palaeognathae in their Bayesian topology, but sister to tinamous in their maximum parsimony and maximum likelihood trees. Maximum likelihood trees inferred using characters exhibiting low homoplasy also supported a position on the palaeognath stem for Lithornithidae [49], though the monophyly of the clade was dependent on the matrix used. Ten non-homoplastic characters from Houde [62] yielded a paraphyletic Lithornithidae, while 92 non-homoplastic characters from Worthy, et al. [136] supported them as a monophyletic group. The authors considered their results as supportive of the hypothesis that all extant palaeognaths evolved independently from Lithornis-like birds [42]. Given lingering uncertainties regarding the monophyly and phylogenetic position of lithornithids, a careful revaluation of character states and species limits within the group would be timely, though this is beyond the scope of the present review.

2.2. African and Eurasian Palaeognaths: Struthioniformes

Two ostrich species are extant. The Common Ostrich Struthio camelus inhabits open areas across much of sub-Saharan Africa, and the Somali Ostrich Struthio molybdophanes of Eastern Africa was once considered conspecific with S. camelus but is now given species status [17,138]. While the two extant species of ostrich are now confined to Africa, their range extended into Asia during the Holocene. Ostriches may have persisted as far east as Mongolia until 7500 years ago based on Carbon-14 dating of eggshells [139] (though see Khatsenovich, et al. [140] regarding uncertainties surrounding the dating of ostrich eggs from Mongolia and Siberia), and ostriches of the subspecies S. c. syriacus, whose native range stretched from the Arabian Peninsula to Syria and Iraq, did not become extinct until 1966 [17]. Ostriches are arguably the most cursorial of all birds, able to run at speeds in excess of 70 km per hour [67]. Their extreme cursoriality is evinced by their unique foot morphology: ostriches are the only extant didactyl birds, an anatomical configuration that may be the result of similar selective pressures as those that drove digit reduction in horses [77]. The fossil record of ostrich eggshell is rich, and although the present review focuses only on skeletal remains, we note that the occurrence of palaeognath eggshells in the early Miocene of China 17 million years ago [77,141] supports the theory that struthionids either originated outside of Africa or else underwent rapid range expansion after their emergence. For a thorough review of the ostrich eggshell record, see Mikhailov and Zelenkov [78].

2.2.1. Eurasian Stem Struthionids

Our understanding of palaeognath evolution and particularly the transition to flightlessness in ratites has been hampered by a lack of recognizable stem group representatives of extant palaeognath lineages. Fortunately, recent research advances have provided a valuable window into the nature of early stem struthionids, which were previously unknown prior to the Miocene. The flightless palaeognaths Palaeotis weigelti and Remiornis heberti have long been known from the Paleogene of Europe [76,142,143,144,145], but their relation to the remainder of Palaeognathae was unclear [76,142]. Palaeotis, the better-known of the two taxa, has been variably recovered as the sister taxon to rheids [146], sister to a clade including Struthionidae, Rheidae, and Casuariidae [147], and sister to a clade comprised of lithornithids and tinamous [33]. The unconstrained analysis of Nesbitt and Clarke [64] recovered Palaeotis outside a Struthio + Dromaius + Rhea clade. When relationships of living palaeognaths were constrained to match those recovered by molecular phylogenies, the same authors recovered Palaeotis as the sister taxon of extant palaeognaths (to the exclusion of lithornithids). Mayr [142] noted the resemblance of the skull of Palaeotis to that of lithornithids, and that the scapulocoracoid differs from all extant ratites, but was unable to find a well-supported placement for Palaeotis and proposed that it may represent yet another independent acquisition of ratite features among palaeognaths. The phylogenetic position of Remiornis heberti was also challenging to estimate with confidence. Mayr [76] considered that it may belong with Palaeotididae before amending this hypothesis based upon the lack of a supratendinal bridge and extensor sulcus in Remiornis, both of which are present in Palaeotis [148].
Without information on its palatal anatomy, it would be extremely difficult to recognize Palaeotis as a palaeognath on the basis of its postcranial skeleton, as several aspects of its hindlimb morphology, such as a notch in the distal rim of the medial condyle of the tibiotarsus and intratendinous ossifications on the tarsometatarsus, are unusual for palaeognaths and are more reminiscent of Gruiformes [148]. Recently, Mayr [148] transferred Galligeranoides boriensis from the stem gruiform clade Geranoididae [149] to Palaeotididae. G. boriensis had been described on the basis of leg bones from the early Eocene of France [150]. Its initial assignment to Geranoididae was notable, as this clade was only known from the Eocene of North America [76,149,151]. The transfer of G. boriensis from Geranoididae to Palaeotididae raises the possibility that additional records of early palaeognaths could be hiding in plain sight in museum collections, misidentified due to their lack of obvious palaeognath synapomorphies.
This scenario was indeed the case with Eogruidae, a group of crane-sized birds known primarily from hindlimb elements from Central Asia. Since the remainder of the skeleton of eogruids was virtually unknown, these taxa were difficult to place phylogenetically. Eocene eogruids show a trend towards reduction in the size of the inner toe as a possible adaptation for cursoriality [152], and later eogruids of the subclade Ergilornithidae take this trend even further, to the point where the inner toe is vestigial or absent [148,152]. This feature led several earlier authors to hypothesize a placement for Eogruidae as stem struthionids [153,154,155]. However, this hypothesis was not widely accepted, and eogruids were generally viewed as representatives of Gruiformes (either as sister to a clade containing Aramidae and Gruidae [156] or sister to Gruidae [149]), implying that the didactyly of some eogruids was convergent with Struthionidae.
A previously undescribed partial skull PIN 3110–170 from the latest Eocene locality of Khoer Dzan, Mongolia has rendered the hypothesis of eogruids as gruiforms untenable [6]. Although the palate is missing, the skull preserves an articular surface for the otic capitulum of the quadrate, but apparently does not exhibit an articular surface for the squamosal capitulum of the quadrate. Both articular surfaces would be expected for a gruiform, and indeed for most neognaths, which have a bipartite otic process of the quadrate. Instead, the skull appears to genuinely exhibit only one articular facet for the quadrate, a condition seen only in palaeognaths [157]. This feature, in combination with the reduction and eventual loss of the inner toe, strongly indicate a stem struthioniform placement for Eogruidae. If taxa with greater toe reduction are more closely related to crown struthionids, eogruids would form a paraphyletic grade along the ostrich stem lineage [6] (Figure 9).
With the reassignment of Eogruidae, there is now a clear record of stem Struthionidae in Eurasia well before the first crown struthionids appear in the Miocene of Africa. It now appears likely that this iconic clade of extant African birds first arose outside the continent. In addition to recognizing eogruids as stem struthionids, Mayr and Zelenkov [6] also hypothesized that Palaeotis represents a total-clade struthionid based upon similarities in the shape of its skull with the newly described specimen. With palaeotidids interpreted as stem struthionids, the case for a Eurasian origin of Struthioniformes is strengthened even further (Figure 9).
The oldest flightless, non-lithornithid palaeognaths in Eurasia belong to Palaeotididae. Galligeranoides boriensis is now the oldest known probable palaeotidid, found in rocks ranging between the ages of 56 to 51 Ma [158]. It is known from a right tibiotarsus, a distal portion of a left tibiotarsus, and an incomplete right tarsometatarsus [150]. The nominate and best known palaeotidid, Palaeotis weigelti, was initially interpreted as a bustard [145] and subsequently as a crane [159] before it was finally recognized as a palaeognath by Houde and Haubold [143], who hypothesized that it was as a stem ostrich despite its lack of obvious cursorial adaptations, an assessment that, in light of the recent work discussed above, has gained robust support. P. weigelti is known from six specimens from the middle Eocene of the Messel and Geisel Valley sites of Germany (Table 2). One of these specimens is a complete two-dimensionally preserved skeleton. It stood slightly under 1 m tall, and was more gracile than the older Remiornis [76].
Eogruids are younger than Palaeotididae, occurring from the middle Eocene to the early Pliocene, and comprise fifteen named species in six genera (Table 2). The oldest species, Eogrus aeola, has been collected from the middle Eocene of Inner Mongolia and Mongolia’s Omnogvi Province [152,166,173] (Table 2). Like nearly all eogruids, it is known only from hindlimb elements. Other members of this genus from the late Eocene include Eogrus crudus from central Mongolia [176], and Eogrus turanicus from Eastern Kazakhstan [174] (Table 2).
Outcrops of the latest Eocene-earliest Oligocene Ergilin Dzo Formation in Dorngovi Province, Mongolia have produced an enormous wealth of eogruid fossils. It is in this formation that Ergilornithidae first appear. Once recognized as a separate family [179], they are now considered a subclade of Eogruidae [156,167]. Ergilornithids recovered from this formation include Ergilornis rapidus [179], Ergilornis minor [176,179], and Sonogrus gregalis [176] (Table 2). The partial skull PIN 3110–170 was collected from the latest Eocene Sevkhul member of this formation [6,155]. As the Sevkhul member has produced huge quantities of hindlimb material belonging to Sonogrus gregalis and Ergilornis minor and no other large birds, the skull was presumed to belong to one of the two species [6].
We were unable to find any documented occurrences of this clade for the remainder of the Oligocene. The ergilornithid genus Urmiornis first appears in the early Miocene, with two occurrences of Urmiornis brodkorbi in western Kazakhstan [180]. The latest occurrence of the genus Eogrus is in the middle Miocene of Inner Mongolia with Eogrus wetmorei [173,182,183]. By the late Miocene, eogruids had expanded their range outside of Central Asia and reached their greatest generic diversity, with Amphipelargus majori occurring on Samos island [167,168] and another member of the same genus on the Greek mainland [167,171], Urmiornis ukrainus occurring in Ukraine, Moldova, and southwestern Russia [166,176], Urmiornis maraghanus in Iran [183,186,189], ?Urmiornis cracrafti in the Siwaliks of northern Pakistan [185], and Sinoergilornis guangheensis in Gansu, China [178] (Table 2). Although Kurochkin [176] noted differences between U. ukrainus and U. maraghanus, the validity of U. ukrainus requires further conformation and U. maraghanus would take nomenclatural priority if they are shown to be the same species [166]. The group continued to thrive in their Central Asian stronghold, with Urmiornis orientalis found near Zaisan, Kazakhstan [166,176] and Urmiornis sp. in the Sunur province of Mongolia and Pavlodar, Kazakhstan [166,176]. The youngest species, Urmiornis dzabghanensis, was found in the early Pliocene Khirgis-Nur Formation of Mongolia [166,188] (Table 2).
The possibility that the eogruids were flightless has been proposed by several authors [152,173], though others contend that such a conclusion is premature based on existing evidence [156,178]. The trochlea for the second toe is vestigial or entirely absent in Ergilornis, Sinoergilornis, Urmiornis, and Ampipelargus [6,166,176,178], which is indicative of a highly cursorial lifestyle as seen in extant struthionids. In addition, a proximal humerus PIN 3110–60 from the Ergilin Dzo Formation attributed to Ergilornis has a greatly reduced deltopectoral crest (the portion of the humerus serving as the major insertion point for major flight muscles), and from this it was assumed that at least this taxon was flightless [152]. If some eogruids were volant, it could imply that multiple transitions to flightlessness occurred among stem struthionids, following the phylogeny of Mayr and Zelenkov (Figure 9) [6].
That the North American Geranoididae may also be struthioniforms has been suggested on several occasions, but unlike Eogruidae no strong evidence for such a placement has yet been found [6,148,155]. Geranoidids share several derived features with Palaeotididae, including an elongated tarsometatarsus, a pronounced extensor sulcus along the dorsal surface of the tarsometatarsus, a proximodistally elongated hypotarsus that forms a long medial crest, and a notched distal rim of the medial condyle of the tibiotarsus [148]. With the recent reassignment of G. boriensis (discussed above), an investigation into possible palaeognath affinities for fossils assigned to the remaining members of this clade is clearly merited. Eogeranoides campivagus from the Wilwood Formation of Wyoming has a deep extensor sulcus along the dorsal surface of the tarsometatarsus, a feature it shares with Palaeotis [142,148]. Considering that North American and European avifaunas were generally similar during the Eocene [114,148], and that certain flightless bird taxa such as Gastornithidae occurred on both sides of the Atlantic [76,77], the possibility that palaeotidids existed in North America is plausible. A clade uniting Palaeotididae, Geranoididae, Eogruidae, and Struthionidae is supported by the following characters highlighted by Mayr and Zelenkov [6]: a very long and narrow tarsometatarsus, a short trochlea for digits II and IV, a tubercle adjacent to the supratendinal bridge, and a shortening of all non-ungual phalanges on pedal digit IV.
Also uncertain is the placement of Remiornis heberti [144] from the late Paleocene of France [161] (Table 2). It is known from several isolated elements belonging to different individuals that include a tibiotarsus, tarsometatarsus, and fragmentary associated remains [76,161,163]. It appears to have been recognized as a palaeognath based on its overall resemblance to Palaeotis, as the two genera share a deep furrow on the dorsal surface of the tarsometatarsus and a similar configuration of the distal trochleae [76]. Mayr [148] excluded it from Palaeotididae based on its lack of an ossified supratendinal bridge and extensor sulcus, and Mayr and Zelenkov did not include Remiornis at all in their new hypothesis of struthioniform interrelationships [6]. However, in light of the variability exhibited by the supratendinal bridge, extensor sulcus, and hypotarsus among palaeognaths, rejecting a struthioniform affinity for Remiornis may be premature. An ossified supratendinal bridge of the tibiotarsus is present in Tinamidae and Dinornithidae and is variably present in Apterygidae, but is missing from all other crown palaeognaths [137,148]. Worthy et al. [137] note that given its variability in clades including crown Palaeognathae and Cariamiformes, the presence or absence of this feature should not be viewed to negate potential sister relationships. The extensor sulcus of the tibiotarsus is also variably present in palaeognaths. It is narrow in Lithornithidae, Apterygidae, Tinamidae, and Dinornithidae, and absent in Struthionidae, Casuariidae, Rheidae, and Aepyornithidae [148]. Eogruids have a hypotarsal canal, while all other palaeognaths lack this feature [148]. The putative gruid Palaeogrus princeps [190] from the middle Eocene of Italy also shares similarities in the distal tibiotarsus with Palaeotis and could represent yet another record of this clade [148].
Several other taxa that deserve further revision of their taxonomic placement are listed here, though it is far less likely that they belong within Palaeognathae. Eleutherornis cotei [191,192] from the middle Eocene of Switzerland and France is known from a partial pelvis and hindlimb elements and was originally assumed to be a ratite due to its large size, but was reinterpreted as a phorusrhacoid [193]. Eremopezus eocaenus [194] is known from hindlimb elements from the late Eocene Fayum Formation of Egypt [76,195]. Rasmussen, et al. [195] suggest that it could represent a non-palaeognathous endemic African group that independently became large and flightless. More material will be needed to firmly rule out palaeognathous affinities for this taxon [76]. Whether or not these species are indeed palaeognaths, we expect that further revaluation of Paleogene fossil collections is bound to reveal more palaeognaths from a critical time period that may capture their transitions to flightlessness.

2.2.2. African and Eurasian Crown Struthionids

As shown in Table 3.
The body fossil record of crown ostriches begins 21 million years ago in the early Miocene of Africa with Struthio coppensi (Figure 7, Table 3), named on the basis of the shaft and distal part of a left tibiotarsus, proximal left femur, distal left tarsometatarsus, right tarsometatarsus shaft, and a left fibula from the early Miocene of the Northern Sperrgebiet, Namibia [197]. As noted by Mourer-Chauviré [198], it was smaller and more gracile than S. camelus, and a vestigial trochlea metatarsi II shows this early ostrich was didactyl [197,198]. A late middle Miocene ostrich from western Kenya assigned to Struthio also had a didactyl foot and was smaller than extant ostriches, though still larger than S. coppensi [200]. Other Kenyan middle Miocene ostrich fossils have been discovered, but they remain undescribed [78,261]. A distal tarsometatarsus was found from the middle-late Miocene boundary in Tunisia [201,202], indicating their presence in North Africa. The size of this bone is roughly comparable with that of the extant S. camelus [78].
No late Miocene ostrich body fossils have yet been found from sub-Saharan Africa, but they are relatively common in Eurasia during this period (Figure 7, Table 3) [78]. A pedal phalanx from the middle Miocene of Turkey is the oldest body fossil of crown struthionids outside Africa [213]. From the late Miocene onwards, this clade occupied an enormous geographical range, from the Balkans to northeastern China and eastern Siberia, and south to India. The oldest ostrich from Eastern Europe, Struthio orlovi, was found in the early late Miocene of Moldova [236]. Late Miocene Southern and Eastern European ostrich species limits are somewhat contentious. S. karatheodoris [245] was larger than extant ostriches [78], and many specimens from the Balkans have been referred to this taxon [238,239,240,242,249]. A large pelvis from the late Miocene of the United Arab Emirates was assigned to this species based on its size [215], and sacral vertebrae of a very large ostrich found in the terminal Miocene of northern Kazakhstan [188,216] may also belong to S. karatheodoris [78]. S. novorossicus [243] is considered a nomem dubium by Mikhailov and Zelenkov [78], as it cannot be distinguished from S. asiaticus. Koufos, et al. [240] suggested that S. brachydactylus [250] may be a junior synonym of S. karatheodoris, but Mikhailov and Zelenkov [78] consider them separate taxa, as S. brachydactylus was roughly the size of S. camelus and therefore much smaller than S. karatheodoris. Mikhailov and Zelenkov [78] refer Palaeostruthio sternatus [244] to S. karatheodoris, creating the new combination Palaeostruthio karatheodoris.
Struthio (“Orientornis”) linxiaensis from the late Miocene of Gansu province, China is one of the oldest East Asian ostriches [77,218,262]. Slightly larger than S. camelus, Mikhailov and Zelenkov [78] argued that it likely belongs in its own genus, but tentatively treat it as Struthio. Other late Miocene Asian ostriches include S. wimani, known from a fragmentary pelvis from China [220], and S. asiaticus [263] from the Siwalik series in North India and Pakistan. The latter species has been treated as somewhat of a wastebasket taxon, with eggshell fragments attributed to it from sediments as young as the late Pleistocene of the Baikal region [264], and body fossils from as far away as South Africa [204,205] (Table 3). Ostrich eggshells ranging in age from 11 to 1.3 Ma are known from the Siwalik series [223]. However, the distribution, temporal range, and taxonomic identifications of these specimens are in need of revision.
Several large ostriches are known from the Pliocene. S. transcaucasius is known from a pelvis from the late Pliocene of Georgia [251] and was recently assigned to the genus Pachystruthio [258]. Many others have not been assigned to a species level taxon. It is evident from hindlimb fragments that a large ostrich existed in the lower Pliocene of South Africa, which was referred to Struthio cf. asiaticus [204,205]. Pliocene fossils from Ahl al Oughlam, Casablanca, Morocco, were also attributed to S. asiaticus [207]. Another large ostrich is known from the early Pliocene of Central Turkey [229]. An ostrich from Odessa, Ukraine, also from the early Pliocene, has only been assigned to Struthio [78,244].
Multiple species of large ostriches persisted through the Pleistocene. Struthio oldawayi of the early Pleistocene of Tanzania was similar to the extant S. camelus, though considerably larger [209,220]. Large Pleistocene ostrich bones from Kenya’s Olduvai Gorge site may also belong to this species [210]. A large ostrich from the early Pleistocene of Algeria was assigned to S. barbarus [201,211], and a middle Pleistocene cervical vertebra from the Nefud desert in northeastern Saudi Arabia bears a close resemblance to the extant S. molybdophanes [265]. Two giant Eurasian ostriches of the early Pleistocene, Pachystruthio pannonicus and Struthio dmanisensis, may be one species [258]. These birds were truly massive; a femur from the lower Pleistocene Taurida Cave of Crimea yields a mass estimate of 450 kg [258] using the equation of Field, et al. [266]. A 1.8-million-year-old right femur from Nihewan, North China may also belong to Pachystruthio. Assigned to Pachystruthio indet., its estimated mass is a smaller, though still enormous 300 kg [233]. S. anderssoni of the late Pleistocene of eastern China [234] was 1.5 times the size of S. camelus, at about 270 kg based on estimates from its minimum femur circumference [267]. Why ostriches disappeared across Eurasia remains a mystery. One hypothesis is that their decline was at least partially linked to climatic cooling throughout the Cenozoic [77]. However, fossil eggshells indicating the possible persistence of ostriches in Mongolia well into the Holocene [139] (though again, see Khatsenovich, et al. [140]) would seem to negate such an explanation, and a stronger explanation for their disappearance is needed.

2.3. South American Palaeognaths: Rheiformes and Tinamiformes

South America is notable for being the only continent to host two family-level palaeognath clades that have persisted to the present day. Two species belong to Rheidae, the Greater Rhea Rhea americana and the Lesser Rhea or Darwin’s Rhea Rhea pennata (alternatively Pterocnemia pennata in certain taxonomies). Both species are cursorial and inhabit open areas, with the Greater Rhea’s range covering much of eastern and southern South America while the Lesser Rhea is found in Patagonia and the Altiplano region [68,268,269]. The Lesser Rhea was formerly placed in its own genus, Pterocnemia, but genetic studies suggest it is closely related to the Greater Rhea, with which it can hybridize [268,270]. There is some debate surrounding species limits among Lesser Rheas populations, as some consider the Altiplano subspecies R. p. garleppi and R. p. tarapacensis to form a separate species from the nominate Patagonian subspecies, R. p. pennata [268].
Tinamous (Tinamidae) are by far the most speciose extant palaeognath clade, and occupy a wide range of habitats in Central and South America [14]. The clade is divided into two major subclades, the forest-adapted Tinaminae which contains 29 species in the genera Tinamus, Crypturellus, and Nothocercus, and the open and arid habitat-dwelling Nothurinae, with 17 species in the genera Taoniscus, Nothura, Nothoprocta, Rhynchotus, Eudromia, and Tinamotis [14,42,271,272]. Like many ground-dwelling birds, tinamous have short wings relative to their body size which results in high wing loading [273]. High wing loading is associated with rapid flight but makes flight energetically costly [273], therefore tinamous tend to escape from threats on foot unless flight is necessary [61]. The pectoral muscles in tinamids are enormous relative to their body size, and allow for rapid takeoff to escape potential predators [273,274].

2.3.1. Rheid Fossil Record

The oldest named ratite, Diogenornis fragilis, provides a key minimum-bound age estimate for the evolution of larger body size and flightlessness among palaeognaths. The type specimen was found in the middle-late Paleocene of Itaboraí, Brazil and consists of limb bones, vertebrae, and the tip of a premaxilla deriving from several individuals [76,275]. The precise age of the Itaboraí fauna has been subject to debate, and an early Eocene age has also been suggested [276]. However, the distal end of a right tibiotarsus missing most of its lateral condyle from the even older middle Paleocene Rio Chico Formation of Argentina was also referred to this genus [277]. It was about two-thirds the size of the Greater Rhea, and its wings were less reduced [77]. For biogeographical reasons, Diogenornis is often presumed to be a stem rheiform [77,275]. However, Alvarenga [278] reported casuariid affinities for Diogenornis, and [277] also noted dissimilarities between the referred tibiotarsus and those of rheids. The cranial end of the medial condyle in medial view is larger and projects further distally than the caudal portion, which optimizes as a synapomorphy of casuariids [5,29]. While we consider it unlikely that Diogenornis represents a casuariiform, the phylogenetic affinities of these fossils remain somewhat uncertain. We conservatively treat D. fragilis as a total-clade rheid (Figure 7, Table 4). Another possible Paleogene rheid is represented by pedal phalanges from the middle Paleocene of Patagonia [279].
Other apparent ratite fossils from South America whose relations to modern palaeognaths are unclear are an incomplete right tibiotarsus from the middle Paleocene Koluel Kaike Formation of Argentina [277], a pedal phalanx from a poorly dated portion of the Sarmiento Formation that could be anywhere between middle Eocene and early Miocene in age [283], and a distal end of a tibiotarsus from the late Miocene of Patagonia [277]. By the late Miocene there was a marked increase in aridity across the continent, in contrast with the paratropical and warm temperate forests that stretched all the way south into Patagonia before this time [307]. Agnolín [277] puts forth the idea that this environmental change could have led to the extinction of hypothetical forest-adapted non-rheid ratites in South America, while favouring the open-habitat adapted rheids. Due to the high degree of anatomical homoplasy among the various ratite lineages, we may never know the true affinities of Diogenornis and these other unnamed ratite-like fossils with certainty, and can only hope that further fossil material will be found that can shed light on their proper phylogenetic placement and ecological habits.
Eocene bird records from South America are unfortunately rare in general [308]. The next oldest rheid fossils are significantly younger, dating from the Miocene (Figure 7, Table 4). Pterocnemia mesopotamica was found in the late Miocene of the Mesopotamia region of Argentina [295], and an isolated tarsometatarsus referred to Pterocnemia cf. mesopotamica could extend the temporal range of this species back to the middle Miocene [295]. Opisthodactylus kirchneri, another rheid from the late Miocene, was described on the basis of a right femur, a right and left tibiotarsus, left and right tarsometatarsi, and pedal phalanges [303]. The robust rheid Hinasuri nehuensis is known from a single left femur from the early Pliocene of Buenos Aires province, Argentina [309]. Extant rheid species appear in the Pleistocene, with Rhea anchorenensis [310] and Rhea pampeana [311] of the Pleistocene of Argentina reassigned to the extant Greater Rhea (Rhea americana) [312,313].

2.3.2. Tinamid Fossil Record

The oldest fossils belonging to crown group Tinamidae appear in the early Miocene Pinturas and Santa Cruz Formations of southern Patagonia (Figure 7, Table 5) [314,315,316]. This apparently abrupt appearance is most likely an artefact of the region’s limited Eocene record. Molecular divergence time estimates suggest that the origin of crown Tinamidae occurred in the late Eocene or early Oligocene, concurrent with large-scale cooling and the emergence of open habitat in South America that led to turnover of the region’s mammalian fauna [42,317]. Most of these early Miocene fossils are fragmentary and cannot be identified at a generic level, though phylogenetic analyses placed them within the open habitat-specialised tinamid subclade Nothurinae [42,315]. A left humerus from the Santa Cruz Formation was described as a new species, Crypturellus reai (Crypturellus is an extant genus within the tinamid subclade Tinaminae, which is sister to Nothurinae [316]). Fragmentary remains from the late Miocene were assigned to the extant genera Eudromia and Nothoprocta [300], both of which belong to Nothurinae. Only two species have been assigned to genera that are no longer extant: Roveretornis intermedius and Tinamisornis parvulus, both from the early Pliocene Monte Hermoso Formation [306,318], and Tinamisornis was later referred to the extant genus Eudromia [319]. The extinct Eudromia olsoni was also described from the same formation [320], and Nothura parvula was found alongside the extant Nothura darwinii and Eudromia elegans in the late Pliocene Chapadmalal Formation [308,321,322]. More recently, Nothura parvula was placed as sister to a Nothura + Taoniscus + Rynchotus + Nothoprocta clade [42]. As-yet undiscovered representatives of the Tinamidae stem group, which will likely be Eocene in age, are sorely needed to better understand the evolutionary history of this group, and whether the ancestors of crown tinamids were adapted for flight styles other than the highly specialized burst flight seen in tinamous today.

2.4. Australian Ratites: Casuariiformes

Both the cursorial emu and the graviportal cassowary belong to the family-level clade Casuariidae [325]. The Emu Dromaius novaehollandiae is the only member of its genus, with the recently extinct dwarf Kangaroo Island Emu D. baudinianus [326], King Island Emu D. minor [327], and Tasmanian Emu D. diemenensis [328] now considered to be subspecies of D. novaehollandiae [329,330,331]. Emu are found across most of continental Australia, with the exception of areas of sandy desert and dense forest [332]. Cassowaries have an extremely distinctive appearance, with a casque on the head and wattles on the neck. Unlike Emu, cassowaries typically inhabit dense rainforest habitats. Three cassowary species are currently accepted: the Southern Cassowary Casuarius casuarius, the Dwarf Cassowary Casuarius bennetti, and the Northern Cassowary Casuarius unappendiculatus [66]. All three species inhabit the island of New Guinea, and the Southern Cassowary’s range extends into northeastern Queensland, Australia, and some adjacent islands. No casuariiform fossils are known before the Late Oligocene [333], and thus far there is no indication that any other palaeognath lineage has ever been present in Australia (Figure 7, Table 6).
One of these earlyfossil Casuariiformes, Emuarius gidju [337], had a temporal range spanning from approximately 24 Ma to 15 Ma and is known from a large number of specimens [341]. E. gidju was first described on the basis of a distal tibiotarsus, proximal tarsometatarsus and shaft, and a complete pes from the Lake Ngapakaldi Leaf Locality of the Wipajiri Formation in South Australia [336]. Two more specimens were found in late Miocene deposits in Alcoota, Northern Territory [336,356], and even more from formations spanning the late Oligocene to early late Miocene of Riversleigh, Queensland [337,340]. The genus Emuarius differs from Dromaius in its retention of a cassowary like-femur, while the tibiotarsus and tarsometatarsus have cursorial modifications and are emu-like [337,340]. The pedal phalanges are of an intermediate morphology between the extant emu and cassowary, being more dorsoventrally compressed than those of cassowaries but less than those of emu [337,341]. This taxon is frequently used to calibrate molecular divergence dates between Casuarius and Dromaius, and a phylogenetic analysis of morphological characters provided robust confirmation for E. gidju and Dromaius being sister taxa [341]. The derived tibiotarsus and tarsometatarsus of Emuarius and Dromaius likely evolved after the emu-cassowary split as the emu lineage began to evolve towards a more cursorial mode of life [337,341]. The humerus is less reduced than in Dromaius, which may represent the plesiomorphic state of a bird less removed in time from its volant ancestors than extant Emu and cassowaries are [341]. E. gidju was smaller than the extant D. novaehollandiae, with an estimated weight of 19–21 kg [340] compared with 30–55 kg in emus [332]. Smaller orbits than Dromaius indicates Emuarius had smaller eyes relative to its skull, and this feature combined with the limited extent of its cursorial specialisations have been interpreted as being representative of the less open habitats present in Australia before the continent underwent extensive aridification beginning in the latter half of the Miocene [341,357].
Emuarius guljaruba, from the 24.1 Ma late Oligocene Etadunna Formation [333,334,335,336], is known from a single complete left tarsometatarsus [333]. It is larger than E. gidju and most likely a separate species, but its allocation to Emuarius remains provisional because no femur has yet been discovered. The extant genus Dromaius first appears in the middle Miocene Camfield beds of the Northern Territory [336,343]. Dromaius arleyekweke from the late Miocene Waite Formation in the Alcoota scientific reserve, Northern Territory [358] is the oldest named species in this genus. Small and gracile, it is notable in that it exhibits extreme cursorial adaptation, with the tarsometatarsus even more elongated than in D. novaehollandiae [358]. It was a small emu, with an estimated body mass based on tibiotarsus least shaft circumference using the algorithm of Campbell and Marcus [359] between 16 and 17.2 kg [358]. Derived features including a distally flattened external condyle of the distal tibiotarsus, the elongated tarsometatarsus, a reduced trochlea metatarsi II as compared with trochlea metatarsi IV, and a shallow median sulcus of the distal trochlea metatarsi II indicate a close affinity with Dromaius rather than Emuarius [358]. The oldest occurrence of the extant Dromaius novaehollandiae is in the early to middle Pliocene-aged Chinchilla Sands of Queensland [336,346,347]. Another species, Dromaius ocypus, is known from a tarsometatarsus from the Pliocene Tirari Formation of Lake Palankarinna, South Australia [349]. D. arleyekweke was found as the sister taxon of D. ocypus and D. novaehollandiae [358]. With D. ocypus interpreted as less cursorial than either D. arleyekweke or D. novaehollandiae, this relationship implies an independent acquisition of cursoriality in D. arleyekweke or a loss in D. ocypus, which may complicate the traditional view of emu evolutionary history as having involved a trend towards increasing cursorial specialisation [358].
The cassowary fossil record is very poor, likely owing to the clade’s preference for tropical forest habitats in which fossils are unlikely to form or be found. Phalanges found from the late Pliocene-aged Otibanda Formation of Papua New Guinea most closely match the extant C. bennetti in size but do not appear similar enough to justify being considered conspecific [351]. Casuarius lydekkeri [353] is known from a distal right tibiotarsus that is likely Pleistocene in age. The provenance of this fossil is debated [355], and may be from Darling Downs, Queensland based on its preservation [331,341]. Worthy, et al. [341] assessed the C. lydekkeri type material and concluded that its placement within Casuarius is likely correct, but there are significant differences between it and the extant C. bennetti and C. casuarius. A partial skeleton from swamp deposits dating to the late Pleistocene of Pureni, Papua New Guinea was assigned to C. lydekkeri, and it was noted to be smaller than any extant cassowary, with a more gracile femur [355]. Unfortunately, no elements from this specimen overlap with those from the Otibanda Formation specimen [355], so the relationship between the only known fossil cassowaries remains a mystery. Naish and Perron [360] speculated that crown cassowaries may be a relatively young clade that evolved in post-Pliocene Australia, with movement into New Guinea occurring during the Pleistocene with the appearance of land bridges between the two landmasses. Of course, this scenario will remain purely speculative until more of these elusive fossils come to light.

2.5. New Zealand Ratites: Apterygiformes and Dinornithiformes

Until just a few centuries ago, New Zealand hosted two ratite lineages: Apterygiformes (kiwi) and Dinornithiformes (moa). Without mammalian competition, kiwi and moa filled the niches of small terrestrial insectivorous and large browsing mammals respectively. Five extant species of kiwi (Apterygidae) are currently recognized, all in the same genus: the Southern Brown Kiwi Apteryx australis, the North Island Brown Kiwi Apteryx mantelli, the Great Spotted Kiwi Apteryx haastii, the Little Spotted Kiwi Apteryx owenii, and the Okarito Brown Kiwi Apteryx rowi [10]. Convergence between kiwi and small ground mammals is often noted, and is indeed remarkable [361]: kiwi are relatively small-bodied and nocturnal, with hair-like plumage and a superb sense of smell that compensates for their poor vision. Their long bills are used to probe the soil and leaf litter for invertebrates. Their eggs, which are the largest relative to body size of any bird, are laid in burrows [10]. Additionally, they are unique in that they are the only known crown birds with two functioning ovaries [362]. All five species face serious threats from introduced mammalian predators, and introduction of kiwi to predator-free offshore islands has been key to their continued survival [363]. Because of their sedentary nature, substantial local diversity exists, and a study examining thousands of mtDNA loci found 16 to 17 genetically distinct lineages within the five extant kiwi species [364].
Moa took the trend of forelimb reduction in flightless birds to the furthest possible extreme by losing the forelimbs entirely. There is no indication of a humeral articular facet on the scapulocoracoid, which itself is highly reduced and, along with the sternum, is the only vestige of the pectoral girdle [77]. A vestigial furcula is present in the genus Dinornis but is absent in all other moa [77]. Curiously, the forelimb-specific gene tbx5 that is essential for the induction of forelimb development appears to have been fully functional in moa, suggesting that other developmental pathways were responsible for the loss of their wings [365]. The moa clade exhibited an extreme degree of reverse sexual dimorphism that for some time led to confusion regarding the number of known species-level taxa. The accepted number of recent taxa based on ancient DNA is nine species in three families: Dinornithidae, containing Dinornis robustus and Dinornis novaezealandiae, Megalapterygidae containing the monotypic Megalapteryx didinus, and Emeidae, containing Anomalopteryx didiformis, Emeus crassus, Euryapteryx curtus, Pachyornis geranoides, Pachyornis elephantopus, and Pachyornis australis [11]. In the largest-bodied genus, Dinornis, females could be up to three times larger than males, and it required a study of ancient sex-linked DNA sequences to reveal that individuals of the previously recognized D. struthoides actually represented the much smaller males of D. giganteus and D. novaezealandiae [366]. The extinction of moa is believed to have occurred extremely rapidly, within 200 years of human settlement approximately 600 years BP [367]. Evidence of their existence remains in New Zealand’s flora, some of which retains anachronistic defenses against browsing by moa [368,369]. Moa coprolites and preserved gizzard contents indicate that they were generalist herbivores, though some degree of species-specific dietary niche partitioning existed [370].
How and when moa and kiwi arrived in New Zealand is still unknown [371], as unfortunately neither group has a clear fossil record from before the Pliocene [372]. Molecular phylogenetic evidence generally supports the hypothesis that moa and tinamous are sister taxa [371], suggesting that moa and kiwi colonised New Zealand and became flightless independently. Depending on the timing of their arrival, both clades may have been greatly affected by the Oligocene drowning of New Zealand, which culminated 25 Mya [373,374]. Coincidentally, this time frame appears to have been a key interval for the emergence of recognizable crown group representatives of other palaeognath clades on different landmasses (Table 3, Table 4, Table 5 and Table 6).
Debates regarding how much of Zealandia was above water during the Oligocene drowning episode, and how this event impacted the origins of New Zealand’s endemic flora and fauna continue [375,376]. Cooper and Cooper [377] postulate that only 18% of the present land area was above sea level during peak inundation as a low-lying archipelago. Trewick, et al. [376] and Landis, et al. [374] proposed that the islands were inundated completely, meaning that the entirety of New Zealand’s terrestrial flora and fauna must have arrived in the past 22 million years. An increasing amount of biological evidence suggests at least some land must have remained above sea level during this period and has shifted the consensus against a total inundation [372]. Divergence dating of taxa with poor dispersal ability including frogs of the genus Leiopelma [378], Craterostigmus centipedes [379], mite harvestmen [380], and zopherid beetles [381] indicates that taxa within these groups diverged well before the drowning event, suggesting that all of them would have needed to independently disperse to New Zealand post-flooding had it been fully submerged. Wallis and Jorge [382] reviewed 248 published divergence dates between New Zealand lineages and their closest relatives elsewhere and found evidence for 74 lineages that diverged before 23 Mya, and of those, 25 lineages dated back before Zealandia split from Australia, making them of true Gondwanan vicariant origin. Interestingly, they found no evidence for a spike in extinctions or new arrivals around the time of the transgression. No study has yet presented unequivocal geological evidence for complete submergence [376,383], and clastic sediments deposited during the Waitakian stage in the southern Taranaki Basin suggests a nearby terrestrial sediment source [384].
Cooper and Cooper [377] examined mitochondrial genetic diversity in kiwi, moa, and acanthisitid wrens and found it to be unusually low compared to other ratites and other avian taxa, and interpreted this as evidence for a bottleneck effect due to the Oligocene drowning. They estimated that re-radiation of these endemic New Zealand lineages began 19–24 Mya. Could this be evidence that moa and kiwi survived the drowning in situ on small islands, or that small volant founding populations arrived afterwards? The apparent survival through the drowning event by other New Zealand taxa means the first scenario is certainly possible. If absence of volant non-tinamid palaeognaths after the middle Eocene is not an artifact of the fossil record, then the ancestral founding populations that ultimately gave rise to kiwi and moa must have arrived before the drowning of New Zealand. Ultimately, only new fossil discoveries from before the drowning event are likely to be able to resolve this question completely.

2.5.1. Apterygid Fossil Record

The oldest kiwi and moa fossils are from the St. Bathans terrestrial vertebrate faunal assemblage from the early Miocene of St. Bathans, in the central Otago region of the South Island (Figure 7, Table 7). The site is dated to 19–16 Ma [385,386], and has provided a rare glimpse at New Zealand’s Neogene fauna just after the drowning of New Zealand. The earliest known kiwi, Proapteryx micromeros, was described on the basis of a right femur missing its distal condyles [387]. The only referred specimen is also fragmentary, consisting of a left quadrate missing the orbital process anterior to the pterygoid condyle and much of the lateral mandibular condyle [387]. Based on the femur circumference, the estimated body mass of P. micromeros was between 234.1 and 377 g, making it only slightly larger than the smallest extant kiwi, A. owenii [387]. If this species is representative of size of the earliest total-clade apterygids, its size would seem to refute the hypothesis that kiwi are phyletic dwarfs. The classic explanation for the extremely large eggs of kiwi was that kiwi evolved from a large-bodied ancestor, and body size decreased over time while egg size remained the same [361,388,389]. Instead, it may be more likely to have arisen as a novel feature related to producing highly precocial young [387,390]. Based on the gracile shape of the femur, the authors went as far as to propose that P. micromeros may have been volant, though that hypothesis is impossible to assess on the basis of presently known fossil material. If P. micromeros was volant, it would represent the only known example of a volant stem member of an extant ratite lineage, and would indicate that kiwi may have arrived in New Zealand after the drowning event. Recently, a 1-million-year-old kiwi fossil from the North Island [391] was identified as a new species Apteryx littoralis [392]. No other fossils of intermediate age are yet known between the St. Bathans fauna and the Holocene, making it difficult to trace the origins of crown kiwi.
Thus far, the only molecular studies that sample multiple Apteryx species yield alternative estimates of the timescale over which species-level diversification within Apteryx took place. Using concatenated sequences of nuclear and mitochondrial DNA, Grealy, et al. [41] estimated that Apteryx mantelli diverged from other kiwi approximately 13 MYA, whereas A. haastii and A. owenii diverged at about 4 MYA. The phylogenomic time tree produced by Yonezawa, et al. [49] included nuclear and mitochondrial sequences from all five extant kiwi species, and is in agreement with those divergence time estimates, inferring an origin of crown group kiwi at approximately 12 MYA. By contrast, Weir, et al. [364] inferred a much younger origin of the kiwi crown group at 3.85 MYA using mitochondrial DNA from a large sample of individuals. This was interpreted as evidence that the kiwi radiation coincided with the last glacial period when populations were isolated in glacial refugia, particularly those on the South Island [364].

2.5.2. Dinornithid Fossil Record

The St. Bathans fauna also provides a window into moa evolution (Figure 7, Table 8), though the moa fossils known from this locality are even more fragmentary than those of kiwi. Eggshell fragments found at the site suggest at least two species of moa were present [372,394,395]. Several large avian bone fragments have been found, including one that was identified as a portion of the proximal shaft of a right tibiotarsus [395]. Other large New Zealand landbirds such as flightless adzebills and giant geese existed at the time, but the fibular and outer cnemial crests are separated further on this tibiotarsus fragment than they would be in those groups, and instead resemble those of palaeognaths most closely [395]. One can only hope that the St. Bathans site yields bones that can be more conclusively identified as belonging to early representatives of the moa lineage. Many late Pleistocene-Holocene moa fossils are known [391,396], but Pliocene-Pleistocene moa fossils are much scarcer, and very few are known from before the Otira glaciation event which began ~75,000 years ago [397]. A tibiotarsus assigned to Euryapteryx was found in marine mudstone reported to be Pliocene in age [397], and Dinornis was present on the North Island at least two million years ago [397]. A tibiotarsus and tarsometatarsus fragments belonging to Anomalopteryx didiformis were found in a clay bed below a basalt [398], and if they are indeed older than the basalt and not fissure-fill, they would be about 2.5 million years old [397].
As with kiwi, molecular time trees have yielded divergent hypotheses regarding the timing of the moa radiation. Bunce, et al. [11] found evidence for the radiation being relatively recent. The deepest divergence (between Megalapterygidae and the remaining family-level moa taxa) was estimated at 5.8 MYA, within the same time frame as rapid mountain formation on the South Island during the Miocene-Pliocene [11]. Indeed, the uplift of the Southern Alps would have led to greater habitat diversity [403], and may have spurred the diversification of moa. Interestingly, Haddrath and Baker [38] placed this earliest moa divergence much earlier, at 19 MYA, which roughly coincides with the end of the Oligocene drowning event. Regardless of when the earliest phylogenetic divergence within the moa clade occurred, the fossil record suggests moa crossed onto the North Island via a land bridge 1.5–2 million years ago, which may have led to even greater species diversity as the land bridge reappeared and disappeared during Pleistocene glacial cycles [11]. Whether kiwi were similarly restricted to the South Island before the Pleistocene is unknown, and more fossils from sediments of intermediate age between the Miocene and Pleistocene are needed to make any further advances.

2.6. Malagasy Ratites: Aepyornithiformes

Extremely little is known of the evolutionary history of Madagascar’s giant elephant birds. The island’s Cenozoic terrestrial vertebrate record is notoriously poor, and thus far all fossil finds are restricted to the last 80,000 years [404,405,406]. What little we do know comes from subfossil bones and eggshells, the latter of which are extremely abundant in some areas. Detailed records of late Pleistocene and Holocene aepyornithid subfossils are beyond the scope of this paper, but can be found in Angst and Buffetaut [407]. Isotopic analysis of eggshells from southern Madagascar reveals that the birds that laid them mainly browsed on non-succulent trees and shrubs [408], some of which retain anachronistic defenses against ratite browsing similar to plants in New Zealand [369]. Palaeoneurological evidence shows that elephant birds had extremely reduced optic lobes, presumably associated with a predominantly nocturnal or crepuscular lifestyle [409].
Even the number of elephant bird species that existed into the Holocene is not known with certainty. Morphometric analysis of subfossil limb bones by Hansford and Turvey [12] recovered evidence for four species-level taxa: Mullerornis modestus, Aepyornis hildebrandti, Aepyornis maximus, and the heaviest bird ever discovered, Vorombe titan. M. modestus, A. maximus, and V. titan were found to be sympatrically distributed across much of Madagascar, while A. hildebrandti was restricted to the central highlands [12]. Molecular studies are needed to evaluate this morphology-based taxonomic scheme, as well as additional fossil collecting in other regions of Madagascar, as most known specimens come from the south of the island and the central highlands [12]. Nuclear and mitochondrial DNA recovered from eggshells suggested that Aepyornis and Mullerornis diverged approximately 27.6 MYA [41]. A divergence at 3.3 MYA between A. hildebrandti and A. maximus had previously been estimated [45]. The third genus found by Hansford and Turvey [12] appears not to have been sampled, highlighting the need to extract aDNA from additional eggshells and subfossil specimens.
Unraveling the decline and eventual demise of elephant birds in Madagascar is less straightforward than for moa, which went extinct within a brief window of time following human arrival in New Zealand [367]. Debate as to how long humans have been present on Madagascar, and thus for how long they coexisted with the island’s endemic megafauna, is ongoing. Based on rare findings of stone tools and butcher marks on elephant bird bones, humans may have arrived early, between 10,000 and 4000 years BP [410,411]. Some anthropologists advocate a more recent arrival, between 1600 and 1000 BP [412], while an intermediate arrival time between 2000 and 1600 BP is supported by 14C data associated with human activity [413]. If humans and elephant birds indeed coexisted for a long period of time, their extinction cannot be easily attributed to the rapid overkill of a naïve population as with moa [411,414]. Instead, a more complex scenario for the extinction of the Malagasy megaherbivores, which also included giant lemurs and tortoises, as well as dwarf hippopotami, has been proposed. Instead of overhunting, the key factor in their decline may have been the introduction of livestock such as Zebu cattle and a shift towards pastoralism. The introduction of large herbivores by humans coincides with the time frame of Malagasy megafaunal extinction, and under this scenario a combination of resource competition with introduced herbivores, alteration of the landscape by humans to suit the needs of livestock, and increased bushmeat hunting due to the expanding human population could have led to the demise of the Malagasy megafauna [414]. Whatever the direct cause or causes, the extinction of Aepyornithidae occurred roughly 1000 years BP according to radiometric data [415], concurrent with the drastic decline and extinction of the remainder of the endemic megafauna of the island [416], though some colonial records suggest they may have survived in isolated areas into the 17th century [407,417].

2.7. Antarctic Ratites

Antarctica was once a very different place from the frozen continent we recognize today. The formation of a continental ice sheet did not occur until the Eocene—Oligocene boundary [418]. Up until this time, the continent boasted thriving flora and fauna that were isolated from large mammalian predators—an ideal environment for flightless birds to evolve. Palynological records from sediment cores dated to 53.6–51.9 MYA from the eastern Antarctic Wilkes Land coast reveal that a diverse paratropical rainforest with frost-free winters existed during the early Eocene climatic optimum [419,420]. Sparse pollen from more cold-tolerant trees such as Nothofagus (southern beech) and Araucaria (“monkey puzzle”) trees suggest temperate rainforests further inland [419,420]. By the middle Eocene, cores from 49.3–46 MYA indicate species diversity had decreased [420] and that cool temperate Nothofagus-dominated forests had taken over [419,420]. As a point of comparison, petrified wood samples from King George island in the South Shetland Islands aged 49–43 MYA (Middle Eocene) indicate a forest similar in composition to the cold temperate Valdivian rainforest of Chile [421], which is not dissimilar to the temperate rain forests of New Zealand that moa once inhabited.
There is fossil evidence of large terrestrial birds in Antarctica during this time, but they are too fragmentary to allow firm diagnoses (Table 9). A distal fragment of a right tarsometatarsus purported to be a ratite was found in the middle Eocene of the La Meseta Formation of Seymour Island, just off the Antarctic peninsula [422]. Unfortunately, there is no evidence for its ratite affinities other than its large size. Its unusually large trochlea for the second toe is different from that of all other known ratites [76], and it bears consideration that misattribution of large bones to ratites is not uncommon [423]. An anterior part of a premaxilla originally attributed to a phorusrhacid, also from the La Meseta Formation [424,425,426,427,428], was recently suggested to belong to a palaeognath [429,430]. The presence of ratites on Seymour Island would not be surprising given the environmental conditions at the time, as evidenced by abundant petrified conifer wood from the La Meseta Formation [431]. Confirmation of their existence will have to await more complete specimens, but remains a tantalizing possibility.
The majority of Cenozoic Antarctic bird fossils belong to penguins and other marine birds, but Seymour Island was also host to a thriving terrestrial fauna during the Eocene. The stem falconid Antarctoboenus carlinii [433,434] was named from a distal end of tarsometatarsus from the early Eocene portion of the La Meseta Formation [430]. Small mammals were abundant, and included the extinct and highly enigmatic sudamericid gondwanatheres [435,436] as well as didelphimorphid, polydolopimorphid, and microbiotheriid marsupials [436,437,438,439,440]. Seymour Island also hosted South American meridiungulates [436,441,442,443,444,445], and a large sparnotheriodont with an estimated body mass of 395–440 kg [446] indicates the ecosystem was fully capable of sustaining large herbivores. The presence of meridiungulates also indicates that overland dispersal from South America was possible, and there is no reason why South American ratites could not have made the journey as well. The Drake passage between South America and the Antarctic Peninsula did not begin to open until approximately 41 Ma [447], meaning these faunas lived during an era where biotic interchange was possible. Such interchange with Australia was also hypothetically possible for a brief window during the Paleocene and early Eocene, as dinocyst assemblages indicate the flow of ocean water across the Tasman gateway by 50–49 Ma [448]. It is also possible for a unique ratite lineage to have arisen on Antarctica, though—as with all other ideas regarding Antarctic palaeognaths—this will remain highly speculative until more fossils are recovered. Regardless of whether the Antarctic terrestrial fauna included ratites, the complete glaciation of the continent in the Oligocene would have doomed them to extinction.

3. Molecular Phylogenetic Hypotheses of Palaeognath Interrelationships

Interpreting phylogenetic relationships among extant and fossil palaeognaths was historically challenging due to morphological homoplasy, and although molecular phylogenetic approaches have yielded some consensus on palaeognath interrelationships, areas of disagreement remain. Thus far, all recent molecular phylogenetic studies of palaeognaths have recovered ostriches as the sister taxon to the rest of the clade, yielding congruent support for a reciprocally monophyletic clade called Notopalaeognathae comprising rheas, tinamous, kiwi, moa, and elephant birds [36,37,38,39,40,41,44,45,46,48,49,50,54,55,56,57,58,449,450]. Limited morphological evidence has also been found in support of a monophyletic Notopalaeognathae [33,77]. In addition, all molecular phylogenetic studies investigating ancient DNA from palaeognath subfossils have strongly supported elephant birds as sister to kiwi [41,45,46,49,57], and tinamous as sister to moa [38,40,41,44,45,46,49,50,57].
The internal relationships of Notopalaeognathae remain controversial, particularly in regard to the position of rheids. The internal branches at the base of Notopalaeognathae appear to be very short, indicating that the clade may have undergone relatively rapid diversification early in its history, which may have led to incomplete lineage sorting and limited phylogenetically informative character acquisition along deep internodes [38,39,56]. This may have pushed Notopalaeognathae into an empirical anomaly zone in which the most common gene trees from molecular phylogenetic analyses do not match the species tree [56]. Rheids are most often recovered in one of two phylogenetic positions:
1. As the sister taxon of the remaining notopalaeognaths [36,37,39,41,42,44,45,46,48,49,54,55,56], though this position is generally weakly supported (Figure 10) [41,44,49].
2. As sister to a casuariid + apterygid + aepyornithid clade (“Novaeratitae”) [38,43,48,50,56,57,58,450] (Figure 11). Several alternative topologies in addition to these have been recovered that place rheas sister to the tinamid-dinornithid clade [37,39,449] or sister to casuariids [38].
Determining why these discrepancies exist could be key to finally resolving the internal branching order of Notopalaeognathae. In their attempt to address this question using genome-wide datasets of conserved nonexonic elements, introns, and ultraconserved elements, Cloutier, et al. [56] found that the consensus species tree building methods MP-EST and ASTRAL-II placed rheids sister to the casuariid-apterygid-aepyornithid clade with maximal bootstrap support from MP-EST for all three datasets. Their concatenated supermatrix dataset recovered rheids as sister to all other notopalaeognaths, but with weaker statistical support. In general, concatenated analyses have often yielded different results to consensus tree building methods regarding the interrelationships of Notopalaeognathae, with concatenated data more frequently recovering rheids as sister to all other notopalaeognaths [56]. Sackton, et al. [50] found similar results and claim that their genome-wide approach is more robust to incomplete lineage sorting than concatenation, which is what leads to discrepancies between studies. “Novaeratitae”, a proposed clade that places casuariids sister to an elephant bird + kiwi clade, received high bootstrap support when mitochondrial and genomic data were combined but not when each were analysed individually [41]. In order to finally resolve the messy internal relationships of notopalaeognaths, a greater number of faster-evolving retrotransposons and introns may need to be analysed [41], and the models of sequence evolution employed must fit the type of genomic data being investigated [58].

Molecular Divergence Time Estimates

The vast majority of molecular divergence time analyses have recovered an estimate for the palaeognath-neognath divergence in the Cretaceous Period, preceding the K-Pg extinction event (e.g., [38,41,42,44,45,47,48,49,54,55,449]), an estimate that is consistent with the known (yet sparse) fossil record of Mesozoic neornithines [72]. However, estimates of the age of the neornithine root vary enormously, ranging from 131 Ma [38] to 63.2 Ma [42]. Importantly, the oldest published divergence time estimates do not invalidate Gondwanan vicariance as a potential driver of crown palaeognath divergences [38]. The enormous temporal breadth of deep neornithine divergence time estimates have stimulated discussion about the role of model misspecification in driving erroneously ancient divergence time estimates [451]. Hypothesized selection for reduced body size across the end-Cretaceous mass extinction event could have transiently increased molecular substitution rates along the deepest branches within neornithine phylogeny, which would be expected to drive overestimates of node ages around the neornithine root [452]. Indeed, simulations suggest that 40 million years’ worth of age disparity for the neornithine root node can plausibly be explained by the effect of body size on nucleotide substitution rates [452]. Importantly, the palaeognath stem lineage is inferred to have exhibited high nucleotide substitution rates, consistent with ancestral palaeognaths having been small-bodied (the last common ancestor of crown palaeognaths was estimated to have weighed approximately 2.9 kg) [452]. With smaller body sizes and shorter generation times than other extant palaeognaths, tinamous exhibit anomalously high nucleotide substitution rates compared with other palaeognaths [37,449], which may additionally drive erroneously ancient divergence time estimates near the neornithine root [45,453].
Lingering uncertainty regarding the phylogenetic divergence times of crown palaeognaths complicates attempts to place lithornithids within the broader context of palaeognath evolution. Since most palaeognath divergence time estimates pre-date the earliest well corroborated lithornithid fossils [41,45,49,449] (with the possible exception of the ~66 million year old isolated scapula from the Hornerstown Formation [63]), the hypothesis that at least some lithornithids represent early stem group representatives of major palaeognath subclades is temporally viable. However, Prum, et al. [48] estimated the origin of the palaeognath crown group at 51 Ma, during the Ypresian stage of the early Eocene. In this temporal scenario, most lithornithid fossils predate the crown palaeognath radiation, in which case nearly all lithornithids with the exception of those found in the younger Messel Formation could only represent stem palaeognaths. This relatively young age for the palaeognath crown group would also imply that early Paleogene remains such as Diogenornis, Palaeotididae, and the Middle Paleocene fossils identified as belonging to a stem rheid fall outside the palaeognath crown group.

4. Key Gaps in the Palaeognath Fossil Record

4.1. Cretaceous Stem Palaeognaths

Virtually no examples of Cretaceous stem palaeognaths have yet been identified, despite consensus—on the basis of divergence time estimates as well as the presence of fossil total-clade neognaths—that they must have existed at this time. This is perhaps the most glaring gap in the known palaeognath fossil record, but is perhaps an unsurprising one given the general scarcity of well-supported Cretaceous neornithines at present. A probable example of a Cretaceous total-clade neognath is Vegavis iaai, recovered from the late Maastrictian of Vega Island, Antarctica [69]. This fossil taxon shows apparent specialisations for foot-propelled diving, and has been variably placed within Anatoidea [69], as a stem neognath, or even outside of Neornithes altogether [72,454]. Asteriornis maastrichtensis, from the Maastrichtian of Belgium, is another probable Cretaceous total-clade neognath. At 66.7–66.8 million years old, Asteriornis is slightly older than Vegavis, and therefore the oldest well-corroborated neornithine yet discovered [72]. A relatively small bird (estimated to have weighed roughly 490 grams), Asteriornis was identified as a total-clade galloanseran [72], although a recent study raised the (weakly supported) hypothesis that it instead represents a total-clade palaeognath [8]. The presence of probable total-clade neognaths from before the K-Pg mass extinction, such as Vegavis and Asteriornis, implies that the palaeognath-neognath split must have occurred even earlier in the Cretaceous (though, as described above, molecular divergence dates do not agree on the true antiquity of the basal neornithine phylogenetic divergence).
Longstanding biogeographic hypotheses held that Neornithes originated in Gondwana [26,55], partly on the basis that there are far more extant endemic bird clades on the southern continents of South America, Africa, and Australia than there are on the northern continents of North America and Eurasia [455]. However, the discovery of Asteriornis in Europe indicates that deeply diverging crown bird lineages have a long evolutionary history in the Northern Hemisphere [72]. More broadly, many clades that are currently restricted to tropical latitudes have fossil stem group representatives in the Paleocene and Eocene of the Northern Hemisphere (e.g., [70,74,120,124,455,456,457]), implying far more widespread geographic distributions early in these clades’ evolutionary histories. Given the generally dispersive capacity of birds, as well as the fact that hothouse climatic conditions predominated throughout the early Paleogene and led to the expansion of paratropical forests into high latitudes, the present-day geographic distributions of many extant tropical clades may not reliably indicate their ancestral areas of origin [74]. In light of these considerations, determining the most likely fossil localities for revealing the first evidence of a Cretaceous stem palaeognath is challenging, and it would seem equally probable that an early palaeognath could derive from Late Cretaceous deposits of either the northern or the southern hemisphere.

4.2. Stem Group Representatives of Extant Palaeognath Subclades

If contemporary hypotheses of ratite paraphyly and dispersal are accurate, small volant palaeognaths should have been present on landmasses where extant palaeognaths are found during the Paleocene or Eocene [45]. However, the timing of each independent palaeognath transition to large body size and flightlessness is uncertain. Transitions to complete flightlessness among island-dwelling birds typically necessitate few terrestrial predators and a food source that does not require flight [458,459]. If these conditions are met, flightlessness may be advantageous because it allows for energy conservation through reduction in the size of the pectoral musculature [460]. Indeed, the basal metabolic rates of flightless rails are lower than those of closely related flighted rails [460]. Given the right circumstances, transitions to flightlessness and large body size can apparently arise quite rapidly. The extinct giant flightless Hawaiian goose Branta rhuax is nested within the Canada Goose Branta canadensis species complex, and its presence on the main island of Hawai’i means it must have become large and flightless in less than 500,000 years [461].
Most geologically recent transitions to avian flightlessness occurred on oceanic islands in the absence of predation and competition from terrestrial mammals [458,459]. Were these conditions met on continents in the wake of the K-Pg mass extinction event, allowing multiple lineages of ratites to evolve flightlessness and large body sizes before mammalian predators and competitors could evolve? These conditions appear to have been met on at least some landmasses, as even 10 million years after the extinction event most mammals remained relatively small and unspecialized [462]. The Corral Bluffs site in Colorado suggests that the mammalian fauna in the immediate aftermath of the K-Pg was dominated by small omnivores and insectivores [463], and generally there was a dearth of specialized mammalian carnivores in the early Paleocene [76,464,465]. The makeup of terrestrial mammalian faunas at the time could well have favoured the evolution of flightlessness in birds that could obtain food on the ground, and other large flightless Paleogene bird clades such as Gastornithidae, Phorusrhacidae, and Dromornithidae may have followed a similar pattern along with ratites [76]. In particular, the lack of placental carnivores in South America through most of the Cenozoic may have contributed to the diversity of flightless birds on that continent, which also included Phorusrhacoidea and the giant anseriform Brontornis [76].
If volant stem group representatives of various palaeognath subclades evolved into large-bodied, flightless forms during a relatively narrow temporal window in the early Paleogene, the chances of finding direct fossil evidence of these small-bodied ancestral forms might be relatively low. Indeed, short internodes near the root of Notopalaeognathae indicate a rapid diversification of palaeognath lineages during the Paleogene [41,56]. However, if some transitions to flightlessness were protracted, the chances of identifying informative fossils documenting such transitions would be more likely. With their recent reassignment to total clade Struthionidae, eogruids are a superb example of previous unrecognised stem group representatives of an extant ratite lineage, though better data on their wing apparatus are needed in order to assess whether all known taxa were flightless. If some taxa were volant, Eogruidae could provide an illuminating window into the relative timing of transitions to cursoriality, large body size, and loss of flight in a ratite lineage.
A further challenging aspect of reconstructing the early evolutionary history of the various ratite lineages is that, if flightlessness and large body size arose numerous independent times, confidently assigning a given volant palaeognath fossil from the Paleogene to the correct palaeognath subclade may prove difficult due to convergence. However, the ongoing exploration of certain localities may yield further insight into transitions to flightlessness among certain ratite lineages—for example, additional finds from the St. Bathans fauna could shed more light on the origins of moa and kiwi, and help elucidate whether the stem kiwi Proapteryx was indeed small and volant as initially hypothesized [387].

5. Reconstructing the Most Recent Common Ancestor of Palaeognaths

Understanding the nature of the most recent common ancestor (MRCA) of extant palaeognaths will reveal much about palaeognath macroevolution, and neornithine macroevolution more broadly. For instance, insight into the flight apparatus of the crown palaeognath MRCA will help explain how the geographic distributions of extant palaeognaths arose. Moreover, stem palaeognaths (along with stem galloanserans and stem neoavians) are inferred to have survived the end-Cretaceous mass extinction event [41,48,71,72], while all non-neornithine birds appear to have perished [73]. Strong evidence regarding the morphology and ecology of early palaeognaths may also help clarify ecological factors that may have favoured the survivorship of crown birds with respect to non-neornithine avialans—one of the more contentious questions in contemporary palaeornithology [71,77]. Inevitably, given that the palaeognath-neognath split is the deepest divergence within crown birds, a better understanding of the nature of the palaeognath MRCA will in turn shed light on the common ancestral condition of all extant birds. Although much remains to be learned, there are several inferences that can be made regarding the nature of the most recent common ancestor (MRCA) of palaeognaths based upon the information currently available.

5.1. The Flight Apparatus of the Crown Palaeognath MRCA

Due to the relaxation of stabilizing selection, significant polymorphism exists in the wing musculature of ratites [466], complicating attempts to infer features of the ancestral crown palaeognath wing. As the only extant flighted palaeognaths, tinamids presumably provide the best source of data on the muscular anatomy of the wings of early flighted palaeognaths. Nearly all flight muscles present in neognaths are found in tinamids, with the exception of the biceps slip [274,467,468]. Extant phylogenetic bracketing [469] therefore indicates that the same suite of muscles would be expected to be present in both the crown palaeognath and crown neornithine MRCAs. Of course, tinamids are specialized for burst flight over relatively short distances, and as such are probably imperfect analogues of the ancestral crown palaeognaths that must have colonized distant landmasses in the early Cenozoic [470]. Subsequent losses of dispersal capacity, and the extinction of dispersive ancestral lineages, can leave the inaccurate impression that poorly dispersive taxa underwent oceanic dispersal via stochastic events. For example, the phasianid galliforms Margaroperdix (Madagascar) and Anurophasis (New Guinea) are poor dispersers, yet are found on isolated islands [470]. Phylogenomic analyses revealed that these taxa are nested within Coturnix quails and likely evolved from a dispersive Coturnix-like ancestor. Both taxa apparently independently evolved towards a non-dispersive partridge-like morphotype, reminiscent of how the ratite condition appears to have repeatedly evolved in palaeognaths [470]. As discussed in this review, some lithornithids appear to have been reasonably capable fliers and could provide more accurate insight into the nature of dispersive ancestral crown palaeognaths.

5.2. Inferred Ecology of the Palaeognath MRCA and K-Pg Survivorship

Non-neornithine avialans thrived throughout the Cretaceous and remained diverse through the Maastrichtian, before suddenly disappearing at the K-Pg boundary [73]. Until this point, Enantiornithes were the dominant Mesozoic avialan clade with more than 60 known species and a worldwide distribution [471,472,473]. Why did they become extinct, while neornithines survived? The answer may be associated with their ecology and habitat preferences. The K-Pg impact was devastating to the world’s forests and resulted in significant species turnover [71,77,474,475,476,477,478]. Palynology of K-Pg boundary sections across the globe indicates that ground cover following the impact consisted primarily of ferns. This “fern spike” is interpreted as evidence of a disaster flora following the destruction of forests worldwide [71,464,474,475,476] by widespread fires ignited by the impact and subsequent cold and darkness [479,480]. This fern spike persisted for approximately 1,000 years, and closed-canopy forests appear to have remained generally rare during this interval [481]. Indeed, it may have taken as long as 1.4 Ma for floral diversity hotspots to reappear [482]. This widespread habitat destruction would have been a powerful agent of selection against the mostly arboreal Enantiornithes, though this hypothesis does not explain the extinction of contemporaneous marine avialans such as Ichthyornithes and Hesperornithes. Instead, the demise of these marine piscivorous taxa may have been part of a broader collapse of marine food chains in the aftermath of the Chicxulub impact [77,81,483,484,485,486]. Importantly, ancestral state reconstructions of crown birds predict that the MRCAs of crown birds and the deepest crown bird subclades (Neornithes, Palaeognathae, Neognathae, and Neoaves) were all non-arboreal [71]. As such, the ancestors of palaeognaths may have made it through this mass extinction event partly by virtue of having exhibited terrestrial non-arboreal lifestyles.
As the most stemward palaeognaths known [49,64], lithornithids provide the best opportunity to draw fossil-informed inferences about the nature of the crown paleognath MRCA. Vibrotactile bill tips in Lithornis promiscuus and Paracathartes howardae may have been associated with probe-feeding in the ground, an interpretation congruent with the hypothesis of predominant K-Pg survivorship among non-arboreal taxa. A vibrotactile bill tip organ composed of mechanoreceptors known as Herbst corpuscles embedded within the bone was hypothesized to be a plesiomorphy of Neornithes by du Toit, et al. [80], which would support the neornithine MRCA and its immediate descendants as having been ground-foraging birds. Such organs are found in palaeognathous and neognathous probe-foragers, enabling them to locate prey buried in substrate through vibration detection [487,488]. In non-probe-foraging palaeognaths, the vibrotactile bill tip organ is vestigial [80,489]. The hypothesis that lithornithids and the palaeognath MRCA were probe-feeders agrees with ideas put forth by Houde [62], who suggested that lithornithids may have preferred to live near water and probed for food using their long beaks, noting the similarity of their jaw apparatus to those of kiwi. Additionally, the genus Lithornis appears to have had relatively large olfactory lobes, similar to olfactory foraging taxa including Procellariiformes and kiwi [490]. Since ground feeding birds are more likely to become flightless than arboreal taxa, a volant, non-arboreal, probe-feeding taxon would seem to be a provide a reasonable expectation for the ecology of the MRCA of crown palaeognaths.

6. Conclusions

Our understanding of palaeognath evolution has progressed markedly over the past two decades thanks to the development and application of sophisticated molecular phylogenetic approaches and the continued interrogation of the fossil record; however, many fundamental questions about the origins of extant palaeognath diversity remain unanswered. The present review affirms that the palaeognath crown group has a reasonably thorough fossil record from the late Oligocene-early Miocene onwards, with the exception of early elephant birds and early representatives of the New Zealand ratites, whose fossil record remains sparse until the Pleistocene [392,397,409]. However, the fossil record still fails to clearly illuminate how and when independent transitions to large body size and flightlessness arose among the multiple lineages of “ratites”. As yet, volant stem members of these extant flightless clades remain unknown (besides the possible exception of Proapteryx [387]), leaving the early evolutionary history of crown group palaeognaths shrouded in mystery. Lithornithids currently provide the best insight into the nature of the earliest total-clade palaeognaths, and their relatively small size, probable non-arboreal ecology, and apparent capacity for sustained flight may make them useful models for understanding the nature of avian survivors of the end-Cretaceous mass extinction event. In the coming years, we anticipate increased consensus on both the evolutionary relationships and age of Palaeognathae and its major subclades, and hope that such advances are accompanied by the recognition of new fossil total-group palaeognaths from the Mesozoic and early Cenozoic. Such advances will be necessary to fill the many gaps in the palaeognath fossil record identified in this review, and to shed light on the repeated independent origins of “ratites”—one of the most striking examples of convergent evolution in birds, or indeed any other vertebrate clade.

Author Contributions

Conceptualization, K.W. and D.J.F.; methodology, K.W. and D.J.F. investigation, K.W.; data curation, K.W.; writing—original draft preparation, K.W.; writing—review and editing, K.W. and D.J.F.; visualization, K.W.; supervision, D.J.F.; funding acquisition, K.W. and D.J.F. All authors have read and agreed to the published version of the manuscript.


This research was funded by UKRI Future Leaders Fellowship, grant number MR/S032177/1 to D.J.F.

Institutional Review Board Statement

Not applicable.


We thank E. Buffetaut and D. Angst for the opportunity to contribute to this Special Issue, K. Welch for proofreading, and G. Mayr as well as an anonymous reviewer for constructive comments on our manuscript.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.


  1. Billerman, S.; Keeney, B.; Rodewald, P.; Schulenberg, T. Birds of the World. Available online: (accessed on 30 March 2021).
  2. Pycraft, W.P. On the Morphology and Phylogeny of the Palæognathæ (Ratitæ and Crypturi) and Neognathæ (Carinatæ). Trans. Zool. Soc. Lond. 1900, 15, 149–290. [Google Scholar] [CrossRef]
  3. Bock, W. The cranial evidence for ratite affinities. In Proceedings of the XIII International Ornithological Congress, Ithaca, NY, USA, 17–24 June 1962; pp. 39–54. [Google Scholar]
  4. Parkes, K.C.; Clark, G.A., Jr. An Additional Character Linking Ratites and Tinamous, and an Interpretation of their Monophyly. Condor 1966, 68, 459–471. [Google Scholar] [CrossRef]
  5. Cracraft, J. Phylogeny and evolution of the ratite birds. Ibis 1974, 116, 494–521. [Google Scholar] [CrossRef]
  6. Mayr, G.; Zelenkov, N. Extinct crane-like birds (Eogruidae and Ergilornithidae) from the Cenozoic of Central Asia are indeed ostrich precursors. Ornithology 2021, 138, 1–15. [Google Scholar] [CrossRef]
  7. Huxley, T.H. On the Classification of Birds and on the Taxonomic Value of the Modifications of Certain of the Cranial Bones Observed in that Class. In Proceedings of the Zoological Society of London; Zoological Society of London: London, UK, 1867. [Google Scholar]
  8. Torres, C.R.; Norell, M.A.; Clarke, J.A. Bird neurocranial and body mass evolution across the end-Cretaceous mass extinction: The avian brain shape left other dinosaurs behind. Sci. Adv. 2021, 7, eabg7099. [Google Scholar] [CrossRef]
  9. Field, D.J.; Benito, J.; Kuo, P.; Jagt, J. Mesozoic Fossil Insight into the Palaeognath-Neognath Anatomical Dichotomy. In Proceedings of the The Society of Vertebrate Paleontology Annual Meeting, Vurtual Meeting, 1–5 November 2021; p. 278. [Google Scholar]
  10. Winkler, D.W.; Billerman, S.M.; Lovette, I.J. Kiwis (Apterygidae), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  11. Bunce, M.; Worthy, T.H.; Phillips, M.J.; Holdaway, R.N.; Willerslev, E.; Haile, J.; Shapiro, B.; Scofield, R.P.; Drummond, A.; Kamp, P.J.J.; et al. The evolutionary history of the extinct ratite moa and New Zealand Neogene paleogeography. Proc. Natl. Acad. Sci. USA 2009, 106, 20646–20651. [Google Scholar] [CrossRef] [Green Version]
  12. Hansford, J.P.; Turvey, S.T. Unexpected diversity within the extinct elephant birds (Aves: Aepyornithidae) and a new identity for the world’s largest bird. R. Soc. Open Sci. 2018, 5, 181295. [Google Scholar] [CrossRef] [Green Version]
  13. Fromm, A.; Meiri, S. Big, flightless, insular and dead: Characterising the extinct birds of the Quaternary. J. Biogeogr. 2021, 1–10. [Google Scholar] [CrossRef]
  14. Winkler, D.; Billerman, S.; Lovette, I. Tinamous (Tinamidae). Birds World 2020. [Google Scholar] [CrossRef]
  15. Cabot, J.; Christie, D.A.; Jutglar, F.; Sharpe, C.J. Dwarf Tinamou (Taoniscus nanus), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  16. Cabot, J.; Jutglar, F.; Garcia, E.F.J.; Boesman, P.F.D.; Sharpe, C.J. Gray Tinamou (Tinamus tao), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  17. Folch, A.; Christie, D.A.; Jutglar, F.; Garcia, E.F.J. Common Ostrich (Struthio camelus), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  18. Davies, S.J.J.F. Moas. In Grzimek’s Animal Life Encyclopedia. Birds I: Tinamous and Ratites to Hoatzins, 2nd ed.; Hutchins, M., Ed.; Gale Group: Farmington Hills, MI, USA, 2003; Volume 8, pp. 95–98. [Google Scholar]
  19. Szabo, M.J. South Island Giant Moa. Available online: (accessed on 18 April 2021).
  20. McDowell, S. The Bony Palate of Birds. Part I The Palaeognathae. Auk 1948, 65, 520–549. [Google Scholar] [CrossRef]
  21. Fürbringer, M. Untersuchungen zur Morphologie und Systematik der Vögel: Zugleich ein Beitrag zur Anatomie der Stütz-und Bewegungsorgane; T. van Holkema: Amsterdam, The Netherlands, 1888; Volume 15. [Google Scholar]
  22. Allen, G.M. Birds and Their Attributes; Marshall Jones Company: Boston, MA, USA, 1925. [Google Scholar]
  23. Stresemann, E. Aves in: Kükenthal-Krumbach, Handbuch der Zoologie. Zool. VII 1927, 7, 2. [Google Scholar]
  24. Verheyen, R. Outline of procedure in basic avian systematics. Gerfaut 1960, 1960, 50. [Google Scholar]
  25. Cracraft, J. Continental drift, paleoclimatology, and the evolution and biogeography of birds. J. Zool. 1973, 169, 455–543. [Google Scholar] [CrossRef]
  26. Cracraft, J. Avian evolution, Gondwana biogeography and the Cretaceous-Tertiary mass extinction event. Proc. R. Soc. B 2001, 268, 459–469. [Google Scholar] [CrossRef] [PubMed]
  27. Roff, D. The evolution of flightlessness: Is history important? Evol. Ecol. 1994, 8, 639–657. [Google Scholar] [CrossRef]
  28. Merrem, B. Tentamen systematis naturalis avium. Abh. Der Königlichen Akad. Der Wiss. Berl. 1813, 237–259. [Google Scholar]
  29. Lee, K.; Feinstein, J.; Cracraft, J. Chapter 7—The Phylogeny of Ratite Birds: Resolving Conflicts between Molecular and Morphological Data Sets. In Avian Molecular Evolution and Systematics; Mindell, D.P., Ed.; Academic Press: San Diego, CA, USA, 1997; pp. 173–209. [Google Scholar]
  30. Livezey, B.C.; Zusi, R.L. Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion. Zool. J. Linn. Soc. 2007, 149, 1–95. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  31. Bourdon, E.; De Riqles, A.; Cubo, J. A new Transantarctic relationship: Morphological evidence for a Rheidae–Dromaiidae–Casuariidae clade (Aves, Palaeognathae, Ratitae). Zool. J. Linn. Soc. 2009, 156, 641–663. [Google Scholar] [CrossRef] [Green Version]
  32. Elzanowski, A. Cretaceous birds and avian phylogeny. Cour. Forsch. Senckenberg 1995, 181, 37–53. [Google Scholar]
  33. Johnston, P. New morphological evidence supports congruent phylogenies and Gondwana vicariance for palaeognathous birds. Zool. J. Linn. Soc. 2011, 163, 959–982. [Google Scholar] [CrossRef] [Green Version]
  34. Owen, R. The Anatomy of Vertebrates, Volume 2: Birds and Mammals; Longmans, Green and Company: London, UK, 1866. [Google Scholar]
  35. Chojnowski, J.L.; Kimball, R.T.; Braun, E.L. Introns outperform exons in analyses of basal avian phylogeny using clathrin heavy chain genes. Gene 2008, 410, 89–96. [Google Scholar] [CrossRef]
  36. Hackett, S.J.; Kimball, R.T.; Reddy, S.; Bowie, R.C.K.; Braun, E.L.; Braun, M.J.; Chojnowski, J.L.; Cox, W.A.; Han, K.; Harshman, J.; et al. A Phylogenomic Study of Birds Reveals Their Evolutionary History. Science 2008, 320, 1763–1768. [Google Scholar] [CrossRef]
  37. Harshman, J.; Braun, E.L.; Braun, M.J.; Huddleston, C.J.; Bowie, R.C.K.; Chojnowski, J.L.; Hackett, S.J.; Han, K.; Kimball, R.T.; Marks, B.D.; et al. Phylogenomic evidence for multiple losses of flight in ratite birds. Proc. Natl. Acad. Sci. USA 2008, 105, 13462–13467. [Google Scholar] [CrossRef] [Green Version]
  38. Haddrath, O.; Baker, A. Multiple nuclear genes and retroposons support vicariance and dispersal of the palaeognaths, and an Early Cretaceous origin of modern birds. Proc. R. Soc. B: Biol. Sci. 2012, 279, 4617–4625. [Google Scholar] [CrossRef] [Green Version]
  39. Smith, J.V.; Braun, E.L.; Kimball, R.T. Ratite Nonmonophyly: Independent Evidence from 40 Novel Loci. Syst. Biol. 2012, 62, 35–49. [Google Scholar] [CrossRef] [Green Version]
  40. Baker, A.J.; Haddrath, O.; McPherson, J.D.; Cloutier, A. Genomic Support for a Moa–Tinamou Clade and Adaptive Morphological Convergence in Flightless Ratites. Mol. Biol. Evol. 2014, 31, 1686–1696. [Google Scholar] [CrossRef] [Green Version]
  41. Grealy, A.; Phillips, M.; Gifford, M.; Gilbert, M.T.P.R.; Jean-Marie Lambert, D.; Bunce, M.; Haile, J. Eggshell palaeogenomics: Palaeognath evolutionary history revealed through ancient nuclear and mitochondrial DNA from Madagascan elephant bird (Aepyornis sp.) eggshell. Mol. Phylogenetics Evol. 2017, 109, 151–163. [Google Scholar] [CrossRef] [PubMed]
  42. Almeida, F.C.; Porzecanski, A.L.; Cracraft, J.L.; Bertelli, S. The evolution of tinamous (Palaeognathae: Tinamidae) in light of molecular and combined analyses. Zool. J. Linn. Soc. 2021. [Google Scholar] [CrossRef]
  43. Feng, S.; Stiller, J.; Deng, Y.; Armstrong, J.; Fang, Q.; Reeve, A.H.; Xie, D.; Chen, G.; Guo, C.; Faircloth, B.C.; et al. Dense sampling of bird diversity increases power of comparative genomics. Nature 2020, 587, 252–257. [Google Scholar] [CrossRef] [PubMed]
  44. Phillips, M.J.; Gibb, G.C.; Crimp, E.A.; Penny, D. Tinamous and Moa Flock Together: Mitochondrial Genome Sequence Analysis Reveals Independent Losses of Flight among Ratites. Syst. Biol. 2009, 59, 90–107. [Google Scholar] [CrossRef] [Green Version]
  45. Mitchell, K.J.; Llamas, B.; Soubrier, J.; Rawlence, N.J.; Worthy, T.H.; Wood, J.; Lee, M.S.Y.; Cooper, A. Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution. Science 2014, 344, 898–900. [Google Scholar] [CrossRef] [Green Version]
  46. Urantówka, A.D.; Kroczak, A.; Mackiewicz, P. New view on the organization and evolution of Palaeognathae mitogenomes poses the question on the ancestral gene rearrangement in Aves. BMC Genom. 2020, 21, 874. [Google Scholar] [CrossRef]
  47. Jarvis, E.D.; Mirarab, S.; Aberer, A.J.; Li, B.; Houde, P.; Li, C.; Ho, S.Y.W.; Faircloth, B.C.; Nabholz, B.; Howard, J.T.; et al. Whole-genome analyses resolve early branches in the tree of life of modern birds. Science 2014, 346, 1320–1331. [Google Scholar] [CrossRef] [Green Version]
  48. Prum, R.O.; Berv, J.S.; Dornburg, A.; Field, D.J.; Townsend, J.P.; Lemmon, E.M.; Lemmon, A.R. A comprehensive phylogeny of birds (Aves) using targeted next-generation DNA sequencing. Nature 2015, 526, 569–573. [Google Scholar] [CrossRef]
  49. Yonezawa, T.; Segawa, T.; Mori, H.; Campos, P.F.; Hongoh, Y.; Endo, H.; Akiyoshi, A.; Kohno, N.; Nishida, S.; Wu, J. Phylogenomics and morphology of extinct paleognaths reveal the origin and evolution of the ratites. Curr. Biol. 2017, 27, 68–77. [Google Scholar] [CrossRef]
  50. Sackton, T.B.; Grayson, P.; Cloutier, A.; Hu, Z.; Liu, J.S.; Wheeler, N.E.; Gardner, P.P.; Clarke, J.A.; Baker, A.J.; Clamp, M.; et al. Convergent regulatory evolution and loss of flight in paleognathous birds. Science 2019, 364, 74–78. [Google Scholar] [CrossRef] [Green Version]
  51. Norberg, U.L. Evolution of flight in animals. Flow Phenom. Nat. 2007, 1, 36–48. [Google Scholar]
  52. Livezey, B.C. Evolution of flightlessness in rails (Gruiformes, Rallidae): Phylogenetic, Ecomorphological, and Ontogenetic Perspectives. Ornithol. Monogr. 2003, 53, iii-654. [Google Scholar] [CrossRef]
  53. Gaspar, J.; Gibb, G.C.; Trewick, S.A. Convergent morphological responses to loss of flight in rails (Aves: Rallidae). Ecol. Evol. 2020, 10, 6186–6207. [Google Scholar] [CrossRef] [PubMed]
  54. Kuhl, H.; Frankl-Vilches, C.; Bakker, A.; Mayr, G.; Nikolaus, G.; Boerno, S.T.; Klages, S.; Timmermann, B.; Gahr, M. An Unbiased Molecular Approach Using 3′-UTRs Resolves the Avian Family-Level Tree of Life. Mol. Biol. Evol. 2020, 38, 108–127. [Google Scholar] [CrossRef] [PubMed]
  55. Claramunt, S.; Cracraft, J. A new time tree reveals Earth history’s imprint on the evolution of modern birds. Sci. Adv. 2015, 1, e1501005. [Google Scholar] [CrossRef] [Green Version]
  56. Cloutier, A.; Sackton, T.B.; Grayson, P.; Clamp, M.; Baker, A.J.; Edwards, S.V. Whole-Genome Analyses Resolve the Phylogeny of Flightless Birds (Palaeognathae) in the Presence of an Empirical Anomaly Zone. Syst. Biol. 2019, 68, 937–955. [Google Scholar] [CrossRef]
  57. Kimball, R.; Oliveros, C.; Wang, N.; White, N.D.; Barker, F.K.; Field, D.J.; Ksepka, D.; Chesser, R.; Moyle, R.; Braun, M.; et al. A Phylogenomic Supertree of Birds. Diversity 2019, 11, 109. [Google Scholar] [CrossRef] [Green Version]
  58. Reddy, S.; Kimball, R.T.; Pandey, A.; Hosner, P.A.; Braun, M.J.; Hackett, S.J.; Han, K.; Harshman, J.; Huddleston, C.J.; Kingston, S.; et al. Why Do Phylogenomic Data Sets Yield Conflicting Trees? Data Type Influences the Avian Tree of Life more than Taxon Sampling. Syst. Biol. 2017, 66, 857–879. [Google Scholar] [CrossRef]
  59. Faux, C.; Field, D.J. Distinct developmental pathways underlie independent losses of flight in ratites. Biol. Lett. 2017, 13. [Google Scholar] [CrossRef]
  60. Farlie, P.G.; Davidson, N.M.; Baker, N.L.; Raabus, M.; Roeszler, K.N.; Hirst, C.; Major, A.; Mariette, M.M.; Lambert, D.M.; Oshlack, A.; et al. Co-option of the cardiac transcription factor Nkx2.5 during development of the emu wing. Nat. Commun. 2017, 8, 132. [Google Scholar] [CrossRef] [Green Version]
  61. Forshaw, J.M. Encyclopedia of Animals: Birds; Merehurst Limited: London, UK, 1991. [Google Scholar]
  62. Houde, P. Paleognathous Birds from the Early Tertiary of the Northern Hemisphere; Paynter, J.R.A., Ed.; Nuttall Ornithological Club: Cambridge, MA, USA, 1988; Volume 22. [Google Scholar]
  63. Parris, D.; Hope, S. New interpretations of birds from the Navesink and Hornerstown formations, New Jersey, USA (Aves: Neornithes). In Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution, Beijing, China, 1–4 June 2002; pp. 113–124. [Google Scholar]
  64. Nesbitt, S.J.; Clarke, J.A. The anatomy and taxonomy of the exquisitely preserved Green River formation (early Eocene) Lithornithids (Aves) and the relationships of Lithornithidae. Bull. Am. Mus. Nat. Hist. 2016, 1–91. [Google Scholar] [CrossRef]
  65. Torres, C.R.; Norell, M.A.; Clarke, J.A. Estimating Flight Style of Early Eocene Stem Palaeognath Bird Calciavis grandei (Lithornithidae). Anat. Rec. 2020, 303, 1035–1042. [Google Scholar] [CrossRef] [PubMed]
  66. Winkler, D.W.; Billerman, S.M.; Lovette, I.J. Cassowaries and Emu (Casuariidae), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  67. Winkler, D.W.; Billerman, S.M.; Lovette, I.J. Ostriches (Struthionidae), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  68. Winkler, D.W.; Billerman, S.M.; Lovette, I.J. Rheas (Rheidae), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  69. Clarke, J.A.; Tambussi, C.P.; Noriega, J.I.; Erickson, G.M.; Ketcham, R.A. Definitive fossil evidence for the extant avian radiation in the Cretaceous. Nature 2005, 433, 305–308. [Google Scholar] [CrossRef]
  70. Ksepka, D.T.; Stidham, T.A.; Williamson, T.E. Early Paleocene landbird supports rapid phylogenetic and morphological diversification of crown birds after the K-Pg mass extinction. Proc. Natl. Acad. Sci. USA 2017, 114, 8047–8052. [Google Scholar] [CrossRef] [Green Version]
  71. Field, D.J.; Bercovici, A.; Berv, J.S.; Dunn, R.; Fastovsky, D.E.; Lyson, T.R.; Vajda, V.; Gauthier, J.A. Early Evolution of Modern Birds Structured by Global Forest Collapse at the End-Cretaceous Mass Extinction. Curr. Biol. 2018, 28, 1825–1831.e2. [Google Scholar] [CrossRef] [Green Version]
  72. Field, D.J.; Benito, J.; Chen, A.; Jagt, J.; Ksepka, D. Late Cretaceous neornithine from Europe illuminates the origins of crown birds. Nature 2020, 579, 397–401. [Google Scholar] [CrossRef]
  73. Longrich, N.; Tokaryk, T.; Field, D.J. Mass extinction of birds at the Cretaceous Paleogene (K-Pg) boundary. Proc. Natl. Acad. Sci. 2011, 108, 15253–15257. [Google Scholar] [CrossRef] [Green Version]
  74. Saupe, E.E.; Farnsworth, A.; Lunt, D.J.; Sagoo, N.; Pham, K.V.; Field, D.J. Climatic shifts drove major contractions in avian latitudinal distributions throughout the Cenozoic. Proc. Natl. Acad. Sci. USA 2019, 116, 12895–12900. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  75. Crouch, N.M.A.; Clarke, J.A. Body size evolution in palaeognath birds is consistent with Neogene cooling-linked gigantism. Palaeogeogr. Palaeoclimatol. Palaeoecol. 2019, 532, 109224. [Google Scholar] [CrossRef]
  76. Mayr, G. Paleogene Fossil Birds; Springer: Berlin/Heidelberg, Germany, 2009; p. 262. [Google Scholar]
  77. Mayr, G. Avian Evolution – The Fossil Record of Birds and Its Paleobiological Significance; Wiley Blackwell: Chichester, UK, 2017; p. 289. [Google Scholar]
  78. Mikhailov, K.; Zelenkov, N. The late Cenozoic history of the ostriches (Aves: Struthionidae), as revealed by fossil eggshell and bone remains. Earth-Sci. Rev. 2020, 208, 103270. [Google Scholar] [CrossRef]
  79. Houde, P.; Olson, S. Paleognathous Carinate Birds from the Early Tertiary of North America. Science 1981, 214, 1236–1237. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  80. Du Toit, C.J.; Chinsamy, A.; Cunningham, S. Cretaceous origins of the vibrotactile bill-tip organ in birds. Proc. R. Soc. B 2020, 287, 20202322. [Google Scholar] [CrossRef]
  81. Clarke, J. Morphology, Phylogenetic Taxonomy, and Systematics of Ichthyornis and Apatornis (Avialae: Ornithurae). Bull. Am. Mus. Nat. Hist. 2004, 286, 1–179. [Google Scholar] [CrossRef]
  82. Benito, J.; Chen, A.; Wilson, L.E.; Bhullar, B.A.S.; Burnham, D.; Field, D.J. 40 new specimens of Ichthyornis provide unprecedented insight into the postcranial morphology of crownward stem group birds. bioRxiv 2022. [Google Scholar] [CrossRef]
  83. Scotese, C.R. PALEOMAP PaleoAtlas for GPlates and the PaleoData Plotter Program. Available online: (accessed on 3 April 2021).
  84. Müller, R.D.; Cannon, J.; Qin, X.; Watson, R.J.; Gurnis, M.; Williams, S.; Pfaffelmoser, T.; Seton, M.; Russell, S.H.J.; Zahirovic, S. GPlates: Building a Virtual Earth Through Deep Time. Geochem. Geophys. Geosystems 2018, 19, 2243–2261. [Google Scholar] [CrossRef]
  85. Olson, S.L.; Parris, D.C. The Cretaceous birds of New Jersey. Smithson. Contrib. Paleobiol. 1987, 63, 1–22. [Google Scholar] [CrossRef]
  86. Staron, R.; Grandstaff, D.; Grandstaff, B.; Gallagher, W. Mosasaur taphonomy and geochemistry implications for a KT bone bed in the New Jersey coastal plain. J. Vertebr. Paleontol. 1999, 19, 78A. [Google Scholar]
  87. Lofgren, D.L.; Lillegraven, J.; Clemens, W.; Gingerich, P.; Williamson, T.; Woodburne, M.O. Paleocene Biochronology: The Puercan Through Clarkforkian Land Mammal Ages. In Late Cretaceous and Cenozoic Mammals of North America; Woodburne, M., Ed.; Columbia University Press: New York, NY, USA, 2004. [Google Scholar]
  88. Stidham, T.A.; Lofgren, D.; Farke, A.A.; Paik, M.; Choi, R. A lithornithid (Aves: Palaeognathae) from the Paleocene (Tiffanian) of southern California. PaleoBios 2014, 31. [Google Scholar] [CrossRef]
  89. Lofgren, D.L.; Honey, J.G.; McKenna, M.C.; Zondervan, R.L.; Smith, E.E.; Wang, X.; Barnes, L. Paleocene primates from the Goler Formation of the Mojave Desert in California. In Geology and Vertebrate Paleontology of Western and Southern North America, Contributions in Honor of David P. Whistler: National History Museum of Los Angeles County Science Series; National History Museum of Los Angeles County: Los Angeles, CA, USA, 2008; Volume 41, pp. 11–28. [Google Scholar]
  90. Albright, L.I.; Lofgren, D.; McKenna, M. Magnetostratigraphy, mammalian biostratigraphy, and refined age assessment of the Goler Formation (Paleocene), California. Mus. North Ariz. Bull. 2009, 65, 259–278. [Google Scholar]
  91. Lofgren, D.; Mckenna, M.; Honey, J.; Nydam, R.; Wheaton, C.; Yokote, B.; Henn, L.; Hanlon, W.; Manning, S.; Mcgee, C. New Records of Eutherian Mammals from the Goler Formation (Tiffanian, Paleocene) of California and Their Biostratigraphic and Paleobiogeographic Implications. Am. Mus. Novit. 2014, 2014, 1–57. [Google Scholar] [CrossRef] [Green Version]
  92. Smith, M.E.; Carroll, A.R.; Singer, B.S. Synoptic reconstruction of a major ancient lake system; Eocene Green River Formation, western United States. Geol. Soc. Am. Bull. 2008, 120, 54–84. [Google Scholar] [CrossRef]
  93. Murphey, P.C.; Evanoff, E. Paleontology and stratigraphy of the middle Eocene Bridger Formation, southern Green River basin, Wyoming. In Proceedings of the 9th Conference on Fossil Resources, Kemmerer, WY, USA, 26–28 April 2011; pp. 83–109. [Google Scholar]
  94. Smith, T.; Smith, R. Terrestrial mammals as biostratigraphic indicators in upper Paleocene-lower Eocene marine deposits of the southern North Sea Basin. Geol. Soc. Am. Spec. Pap. 2003, 369, 513–520. [Google Scholar] [CrossRef]
  95. De Bast, E.; Steurbaut, E.; Smith, T. New mammals from the marine Selandian of Maret, Belgium, and their implications for the age of the Paleocene continental deposits of Walbeck, Germany. Geol. Belg. 2013, 16, 4. [Google Scholar]
  96. Mayr, G.; Smith, T. New Paleocene bird fossils from the North Sea Basin in Belgium and France. Geol. Belg. 2019, 22, 35–46. [Google Scholar] [CrossRef]
  97. Aguilar, J.; Augustı, J.; Alexeeva, N.; Antoine, P.; Antunes, M.; Archer, M. Syntheses and correlation tables. In Proceedings of the Actes du Congres BiochroM, Montpellier, France, 14–17 April 1997; pp. 769–805. [Google Scholar]
  98. Mayr, G. The Birds from the Paleocene Fissure Filling of Walbeck (Germany). J. Vertebr. Paleontol. 2007, 27, 394–408. [Google Scholar] [CrossRef]
  99. Steurbaut, E. High-resolution holostratigraphy of Middle Paleocene to Early Eocene strata in Belgium and adjacent areas. Palaeontogr. Abt. A: Palaozool. Stratigr. 1997, 247, 91–156. [Google Scholar]
  100. Moreau, F.; Mathis, S. Les élasmobranches du Thanétien (Paléocène) du Nord de la France, des carrières de Templeuve et de Leforest. Cossmanniana 2000, 7, 1–18. [Google Scholar]
  101. Heilmann-Clausen, C.; Schmitz, B. The late Paleocene thermal maximum δ13C excursion in Denmark? Gff 2000, 122, 70. [Google Scholar] [CrossRef]
  102. Bourdon, E.; Lindow, B.E.K. A redescription of Lithornis vulturinus (Aves, Palaeognathae) from the Early Eocene Fur Formation of Denmark. Zootaxa 2015, 4032, 493–514. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  103. Chambers, L.; Pringle, M.; Fitton, G.; Larsen, L.; Pedersen, A.; Parrish, R. Recalibration of the Palaeocene-Eocene boundary (PE) using high precision U-Pb and Ar-Ar isotopic dating. In Proceedings of the EGS-AGU-EUG Joint Assembly, Nice, France, 6–11 April 2003; p. 9681. [Google Scholar]
  104. Leonard, L.; Dyke, G.; van Tuinen, M. A New Specimen of the Fossil Palaeognath Lithornis from the Lower Eocene of Denmark. Am. Mus. Novit. 2005, 3491, 1–11. [Google Scholar] [CrossRef]
  105. King, C. The stratigraphy of the London Clay and associated deposits. Tert. Res. Spec. Pap. 1981, 6, 1–158. [Google Scholar]
  106. Ellison, R.A.; Woods, M.A.; Allen, D.J.; Forster, A.; Pharaoh, T.C.; King, C. Palaeogene–Eocene. In Geology of London; British Geological Survey: London, UK, 2004; pp. 44–54. [Google Scholar]
  107. Friedman, M.; Beckett, H.T.; Close, R.A.; Johanson, Z. The English Chalk and London Clay: Two remarkable British bony fish Lagerstätten. Geol. Soc. Lond. Spec. Publ. 2016, 430, 165–200. [Google Scholar] [CrossRef]
  108. Franzen, J.; Haubold, H. The middle Eocene of European mammalian stratigraphy. Definition of the Geiseltalian. Mod. Geol. 1986, 10, 159–170. [Google Scholar]
  109. Schaal, S.; Ziegler, W. Messel: Ein Schaufenster in die Geschichte der Erde und des Lebens; Waldemar Kramer: Frankfurt, Germany, 1988. [Google Scholar]
  110. Lenz, O.K.; Wilde, V.; Mertz, D.F.; Riegel, W. New palynology-based astronomical and revised 40Ar/39Ar ages for the Eocene maar lake of Messel (Germany). Int. J. Earth Sci. 2015, 104, 873–889. [Google Scholar] [CrossRef]
  111. Mayr, G. First substantial Middle Eocene record of the Lithornithidae (Aves): A postcranial skeleton from Messel (Germany). Ann. De Paleontol. 2008, 94, 29–37. [Google Scholar] [CrossRef]
  112. Mayr, G. Towards the complete bird—The skull of the middle Eocene Messel lithornithid (Aves, Lithornithidae). Bull. De L’Institute R. Des. Sci. Nat. De Belg. 2009, 79, 167–173. [Google Scholar]
  113. Blondel, J.; Mourer-Chauviré, C. Evolution and history of the western Palaearctic avifauna. Trends Ecol. Evol. 1998, 13, 488–492. [Google Scholar] [CrossRef]
  114. Mayr, G. Birds–The most species-rich vertebrate group in Messel. Senckenberg Ges. Für Nat. Frankf. Am Main 2018, 169–214. [Google Scholar]
  115. Harrison, C. A new cathartid vulture from the lower Eocene of Wyoming. Tert. Res. 1979, 5, 7–10. [Google Scholar]
  116. Grande, L. Paleontology of the Green River Formation, with a Review of the Fish Fauna, 2nd ed.; University of Wyoming: Laramie, WY, USA, 1984. [Google Scholar]
  117. Wetmore, A. Fossil birds from the Green River deposits of eastern Utah. Ann. Carnegie Mus. 1926, 16, 391–497. [Google Scholar]
  118. Brodkorb, P. An eocene puffbird from Wyoming. Rocky Mt. Geol. 1970, 9, 13–15. [Google Scholar]
  119. Olson, S. A Lower Eocene Frigatebird from the Green River Formation of Wyoming (Pelecaniformes: Fregatidae). Smithson. Contrib. Paleobiol. 1977, 35. [Google Scholar] [CrossRef]
  120. Olson, S. An early Eocene oilbird from the Green River Formation of Wyoming (Caprimulgiformes: Steatornithidae). In Proceedings of the Table Ronde internationale du CNRS, Lyon, France, 18–21 September 1985; pp. 57–69. [Google Scholar]
  121. Olson, S. A new family of primitive landbirds from the early Eocene Green River Formation of Wyoming. Pap. Avian Paleontol. Honor. Pierce Brodkorb 1992, 36, 127–136. [Google Scholar]
  122. Mayr, G.; Daniels, M. A new short-legged landbird from the Early Eocene of Wyoming and contemporaneous European sites. Acta Palaeontol. Pol. 2001, 46, 393–402. [Google Scholar]
  123. Olson, S.; Matsuoka, H. New specimens of the early Eocene frigatebird Limnofregata (Pelecaniformes: Fregatidae), with the description of a new species. Zootaxa 2005, 1046, 1–15. [Google Scholar] [CrossRef] [Green Version]
  124. Ksepka, D.T.; Clarke, J.A. Affinities of Palaeospiza bella and the Phylogeny and Biogeography of Mousebirds (Coliiformes). Auk 2009, 126, 245–259. [Google Scholar] [CrossRef]
  125. Ksepka, D.T.; Clarke, J.A. Primobucco mcgrewi (Aves: Coracii) from the Eocene Green River Formation: New anatomical data from the earliest constrained record of stem rollers. J. Vertebr. Paleontol. 2010, 30, 215–225. [Google Scholar] [CrossRef] [Green Version]
  126. Weidig, I. New birds from the Lower Eocene Green River Formation, North America. In Proceedings of the VII International Meeting of the Society of Avian Paleontology and Evolution, ed. W.E. Boles and T.H. Worthy. Rec. Aust. Mus. 2010, 62, 29–44. [Google Scholar]
  127. Ksepka, D.T.; Clarke, J.A.; Grande, L. Stem Parrots (Aves, Halcyornithidae) from the Green River Formation and a Combined Phylogeny of Pan-Psittaciformes. J. Paleontol. 2011, 85, 835–852. [Google Scholar] [CrossRef]
  128. Smith, N.D.; Grande, L.; Clarke, J.A. A new species of Threskiornithidae-like bird (Aves, Ciconiiformes) from the Green River Formation (Eocene) of Wyoming. J. Vertebr. Paleontol. 2013, 33, 363–381. [Google Scholar] [CrossRef]
  129. Owen, R. Description of the remains of a mammal, a bird, and a serpent from the London Clay. Proc. Geol. Soc. Lond. 1840, 3, 162–166. [Google Scholar]
  130. Owen, R. Description of the Fossil Remains of a Mammal (Hyracotherium leporinum) and of a Bird (Lithornis vulturinus) from the London Clay. Trans. Geol. Soc. 1841, 2, 203–208. [Google Scholar] [CrossRef]
  131. Harrison, C.J.O.; Walker, C.A. Birds of the British Lower Eocene. Tert. Res. Spec. Pap. 1977, 3, 1–52. [Google Scholar]
  132. Harrison, C.J.O. Rail-like cursorial birds of the British Lower Eocene, with descriptions of two new species. Lond. Nat. 1984, 63, 14–23. [Google Scholar]
  133. Bledsoe, A.H. A Phylogenetic Analysis of Postcranial Skeletal Characters of the Ratite Birds. Ann. Carnegie Mus. 1988, 57, 73–90. [Google Scholar]
  134. Mayr, G.; Clarke, J. The deep divergences of neornithine birds: A phylogenetic analysis of morphological characters. Cladistics 2003, 19, 527–553. [Google Scholar] [CrossRef]
  135. Clarke, J.; Zhou, Z.; Zhang, F. Insight into the evolution of avian flight from a new clade of Early Cretaceous ornithurines from China and the morphology of Yixianornis grabaui. J. Anat. 2006, 208, 287–308. [Google Scholar] [CrossRef]
  136. Worthy, T.H.; Mitri, M.; Handley, W.D.; Lee, M.S.Y.; Anderson, A.; Sand, C. Osteology supports a stem-galliform affinity for the giant extinct flightless bird Sylviornis neocaledoniae (Sylviornithidae, Galloanseres). PLoS ONE 2016, 11, e0150871. [Google Scholar] [CrossRef] [Green Version]
  137. Worthy, T.H.; Degrange, F.J.; Handley, W.D.; Lee, M.S.Y. The evolution of giant flightless birds and novel phylogenetic relationships for extinct fowl (Aves, Galloanseres). R. Soc. Open Sci. 2017, 4, 170975. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  138. Del Hoyo, J.; Collar, N.; Garcia, E.F.J. Somali Ostrich (Struthio molybdophanes), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  139. Janz, L.; Feathers, J.K.; Burr, G.S. Dating surface assemblages using pottery and eggshell: Assessing radiocarbon and luminescence techniques in Northeast Asia. J. Archaeol. Sci. 2015, 57, 119–129. [Google Scholar] [CrossRef]
  140. Khatsenovich, A.; Rybin, E.; Gunchinsuren, B.; Bolorbat, T.; Odsuren, D.; Angaragdulguun, G.; Margad-Erdene, G. Human and Struthio asiaticus: One page of Paleolithic art in the eastern part of Central Asia. Irkutsk State Univ. Bull. Ser. Geoarcheol. Ethnol. Anthropol. 2017, 21, 80–106. [Google Scholar]
  141. Wang, S.; Hu, Y.; Wang, L. New ratite eggshell material from the Miocene of Inner Mongolia, China. Chin. Birds 2011, 2, 18–26. [Google Scholar] [CrossRef]
  142. Mayr, G. The middle Eocene European “ratite” Palaeotis (Aves, Palaeognathae) restudied once more. Paläontologische Z. 2015, 89, 503–514. [Google Scholar] [CrossRef]
  143. Houde, P.; Haubold, H. Palaeotis weigelti restudied; a small middle Eocene ostrich (Aves: Struthioniformes). Palaeovertebrata 1987, 17, 27–42. [Google Scholar]
  144. Lemoine, V. Recherches sur les Oiseaux Fossiles des Terrains Tertiaires Inférieurs des Environs de Reims, Deuxième Partie; Matot-Braine: Reims, France, 1881. [Google Scholar]
  145. Lambrecht, K. Palaeotis weigelti n. g. n. sp., eine fossile Trappe aus der mitteleozänen Braunkohle des Geiseltales. Jahrb. Des Halleschen Verb. Für Die Erforsch. Mitteldtsch. Bodenschätze 1928, 7, 1–11. [Google Scholar]
  146. Peters, D.S. Ein vollständiges Exemplar von Palaeotis weigelti (Aves, Palaeognathae). Cour. Forsch. Senckenberg 1988, 107, 223–233. [Google Scholar]
  147. Dyke, G.J. The fossil record and molecular clocks: Basal radiations within Neornithes. In Telling the Evolutionary Time—Molecular Clocks and the Fossil Record; Smith, P., Donoghue, P., Eds.; Taylor and Francis: London, UK, 2003; pp. 263–278. [Google Scholar]
  148. Mayr, G. Hindlimb morphology of Palaeotis suggests palaeognathous affinities of the Geranoididae and other crane-like birds from the Eocene of the Northern Hemisphere. Acta Palaeontol. Pol. 2019, 64, 669–678. [Google Scholar] [CrossRef]
  149. Mayr, G. On the taxonomy and osteology of the Early Eocene North American Geranoididae (Aves, Gruoidea). Swiss J. Palaeontol. 2016, 135, 315–325. [Google Scholar] [CrossRef]
  150. Bourdon, E.; Mourer-Chauviré, C.; Laurent, Y. Early Eocene Birds from La Borie, Southern France. Acta Palaeontol. Pol. 2016, 61, 175–190. [Google Scholar] [CrossRef] [Green Version]
  151. Cracraft, J. Systematics and evolution of the Gruiformes (Class, Aves). 1. The Eocene family Geranoididae and the early history of the Gruiformes. Am. Mus. Novit. 1969, 2388, 1–41. [Google Scholar]
  152. Kurochkin, E. A survey of the Paleogene birds of Asia. Smithson. Contrib. Paleobiol. 1976, 27, 75–86. [Google Scholar]
  153. Burchak-Abramovich, N.I. Urmiornis (Urmiornis maraghanus Mecq.) strausopodobnaya ptitsa gipparionovoi fauny Zakavkaz’a i yuzhnoi Ukrainy [Urmiornis (Urmiornis maraghanus Mecq.), an ostrich-like bird from the Hipparion fauna of Transcaucasia and southern Ukraine]. Izv. Akedemii Nauk Azerbaidzhanskoi SSR 1951, 6, 83–94. [Google Scholar]
  154. Feduccia, A. The Age of Birds; Harvard University Press: Cambridge, MA, USA, 1980. [Google Scholar]
  155. Olson, S.L. The fossil record of birds. Avian Biol. 1985, 79–238. [Google Scholar]
  156. Clarke, J.A.; Norell, M.A.; Dashzėvėg, D. New Avian Remains from the Eocene of Mongolia and the Phylogenetic Position of the Eogruidae (Aves, Gruoidea). Am. Mus. Novit. 2005, 1–17. [Google Scholar] [CrossRef] [Green Version]
  157. Elzanowski, A.; Paul, G.S.; Stidham, T.A. An avian quadrate from the Late Cretaceous Lance Formation of Wyoming. J. Vertebr. Paleontol. 2001, 20, 712–719. [Google Scholar] [CrossRef]
  158. Vandenberghe, N.; Hilgen, F.J.; Speijer, R.P.; Ogg, J.G.; Gradstein, F.M.; Hammer, O.; Hollis, C.J.; Hooker, J.J. Chapter 28—The Paleogene Period. In The Geologic Time Scale; Gradstein, F.M., Ogg, J.G., Schmitz, M., Ogg, G., Eds.; Elsevier: Amsterdam, The Netherlands, 2012; pp. 855–921. [Google Scholar]
  159. Lambrecht, K. Drei neue Vogelformen aus dem Lutétian des Geiseltales. Nova Acta Leopold. 1935, 3, 361–367. [Google Scholar]
  160. Buffetaut, E.; Angst, D. Stratigraphic distribution of large flightless birds in the Palaeogene of Europe and its palaeobiological and palaeogeographical implications. Earth-Sci. Rev. 2014, 138, 394–408. [Google Scholar] [CrossRef]
  161. Martin, L.D. The status of the Late Paleocene birds Gastornis and Remiornis. Nat. Hist. Mus. Los Angeles Cty. Sci. Ser. 1992, 36, 97–108. [Google Scholar]
  162. Smith, T.; Quesnel, F.; De Plöeg, G.; De Franceschi, D.; Métais, G.; De Bast, E.; Solé, F.; Folie, A.; Boura, A.; Claude, J.; et al. First Clarkforkian equivalent Land Mammal Age in the latest Paleocene basal Sparnacian facies of Europe: Fauna, flora, paleoenvironment and (bio)stratigraphy. PLoS ONE 2014, 9, e86229. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  163. Buffetaut, E.; de Ploëg, G. Giant Birds from the Uppermost Paleocene of Rivecourt (Oise, Northern France). Bol. Do Cent. Port. De Geo-História E Pré-História 2020, 2, 1. [Google Scholar]
  164. Laurent, Y.; Adnet, S.; Bourdon, E.; Corbalan, D.; Danilo, L.; Duffaud, S.; Fleury, G.; Garcia, G.; Godinot, M.; Le Roux, G. La Borie (Saint-Papoul, Aude): Un gisement exceptionnel dans l’Éocène basal du Sud de la France. Bull. De La Société D’histoire Nat. De Toulouse 2010, 146, 89–103. [Google Scholar]
  165. Danilo, L.; Remy, J.A.; Vianey-Liaud, M.; Marandat, B.; Sudre, J.; Lihoreau, F. A new Eocene locality in southern France sheds light on the basal radiation of Palaeotheriidae (Mammalia, Perissodactyla, Equoidea). J. Vertebr. Paleontol. 2013, 33, 195–215. [Google Scholar] [CrossRef]
  166. Zelenkov, N.; Kurochkin, E.N. Class. Aves, Iskopaemye Pozvonochnye Rossii i Sopredel’nyh Stran. Iskopaemye Reptilii i Ptitsy. Chast’3; Kurochkin, E., Lopatin, A., Zelenkov, N., Eds.; GEOS: Moscow, Russia, 2015. [Google Scholar]
  167. Zelenkov, N.; Boev, Z.; Lazaridis, G. A large ergilornithine (Aves, Gruiformes) from the Late Miocene of the Balkan Peninsula. Paläontologische Z. 2016, 90, 145–151. [Google Scholar] [CrossRef]
  168. Lydekker, R. Catalogue of the Fossil Birds in the British Museum (Natural History); Order of the Trustees: London, UK, 1891. [Google Scholar]
  169. Tsoukala, E.; Bartsiokas, A. New Mesopithecus pentelicus specimens from Kryopigi, Macedonia, Greece. J. Hum. Evol. 2008, 54, 448–451. [Google Scholar] [CrossRef] [PubMed]
  170. Lazaridis, G.; Tsoukala, E. Hipparion phlegrae, sp. nov. (Mammalia, Perissodactyla): A new species from the Turolian locality of Kryopigi (Kassandra, Chalkidiki, Greece). J. Vertebr. Paleontol. 2014, 34, 164–178. [Google Scholar] [CrossRef]
  171. Boev, Z.; Lazaridis, G.; Tsoukala, E. Otis hellenica sp. nov., a new Turolian bustard (Aves: Otididae) from Kryopigi (Chalkidiki, Greece). Geol. Balc. 2013, 42, 59–64. [Google Scholar] [CrossRef]
  172. Li, Q. Eocene fossil rodent assemblages from the Erlian Basin (Inner Mongolia, China): Biochronological implications. Palaeoworld 2016, 25, 95–103. [Google Scholar] [CrossRef]
  173. Wetmore, A. Fossil Birds from Mongolia and China. Am. Mus. Novit. 1934, 711, 1–16. [Google Scholar]
  174. Bendukidze, O. Novyj prestavitel’ semeist-va Geranoididae (Aves, Gruiformes) iz eotsenovykh otlozhenij Zaisan. Soobtzhenija Akad. Nauk Gruz. SSSR 1971, 63, 749–751. [Google Scholar]
  175. Russell, D.; Zhai, R. The Paleogene of Asia: Mammals and stratigraphy. Mémoires Du Muséum Natl. D’histoire Nat. Série C 1987, 52, 1–488. [Google Scholar]
  176. Kurochkin, E.N. New representatives and evolution of two archaic gruiform families in Eurasia. Tr. Sovmest. Sov. Mong. Paleontol. Ekspeditsija 1981, 15, 59–85. [Google Scholar]
  177. Dashzėvėg, D. Some carnivorous mammals from the Paleogene of the eastern Gobi Desert, Mongolia, and the application of Oligocene carnivores to stratigraphic correlation. Am. Mus. Novit. 1996, 3179, 1–14. [Google Scholar]
  178. Musser, G.; Li, Z.; Clarke, J.A. A new species of Eogruidae (Aves: Gruiformes) from the Miocene of the Linxia Basin, Gansu, China: Evolutionary and climatic implications. Auk 2019, 137. [Google Scholar] [CrossRef]
  179. Kozlova, E.V. Novye iskopaemye ptitsy iz yugovostochnoi Gobi. Tr. Probl. I Temat. Soveshanii ZIN 1960, 9, 323–329. [Google Scholar]
  180. Karhu, A. A new species of Urmiornis (Gruiformes: Ergilornithidae) from the early Miocene of western Kazakhstan. Paleontol. J. 1997, 31, 102–107. [Google Scholar]
  181. Wang, X.; Qiu, Z.; Opdyke, N.D. Litho-, bio-, and magnetostratigraphy and paleoenvironment of Tunggur Formation (Middle Miocene) in central Inner Mongolia, China. Am. Mus. Novit. 2003, 2003, 1–31. [Google Scholar] [CrossRef]
  182. Brodkorb, P. Catalogue of fossil birds. Part 3 (Ralliformes, Ichthyornithiformes, Charadriiformes). Bull. Fla. State Mus. Biol. Sci. II 1967, 3, 1–220. [Google Scholar]
  183. Cracraft, J. Systematics and evolution of the Gruiformes (class Aves). 3. Phylogeny of the suborder Grues. Bull. Am. Mus. Nat. Hist. 1973, 151, 1–128. [Google Scholar]
  184. Barry, J.C.; Morgan, M.E.; Flynn, L.J.; Pilbeam, D.; Behrensmeyer, A.K.; Raza, S.M.; Khan, I.A.; Badgley, C.; Hicks, J.; Kelley, J. Faunal and environmental change in the late Miocene Siwaliks of northern Pakistan. Paleobiology 2002, 28, 1–71. [Google Scholar] [CrossRef]
  185. Harrison, C.; Walker, C.A. Fossil birds from the Upper Miocene of northern Pakistan. Tert. Res. 1982, 4, 53–69. [Google Scholar]
  186. Mecquenem, R. Contribution à l’étude du gisement des vertébrés de Maragha et de ses environs. Ann. D’histoire Nat. 1908, 1, 27–29. [Google Scholar]
  187. Fang, X.; Wang, J.; Zhang, W.; Zan, J.; Song, C.; Yan, M.; Appel, E.; Zhang, T.; Wu, F.; Yang, Y.; et al. Tectonosedimentary evolution model of an intracontinental flexural (foreland) basin for paleoclimatic research. Glob. Planet. Chang. 2016, 145, 78–97. [Google Scholar] [CrossRef]
  188. Kurochkin, E.N. Birds of the central Asia in Pliocene. Trans. Jt. Sov. Mong. Paleontol. Exped. 1985, 26, 1–120. [Google Scholar]
  189. Mecquenem, R. Oiseaux. Contribution à l’étude des fossiles de Maragha. Ann. De Paléontologie 1925, 14, 54–56. [Google Scholar]
  190. Portis, A. Contribuzioni alla ornitolitologia italiana. Mem. Della R. Accad. Delle Sci. Di Torino 1884, 36, 361–384. [Google Scholar]
  191. Schaub, S. Ein Ratitenbecken aus dem Bohnerz von Egerkingen. Eclogae Geol. Helv. 1940, 33, 274–284. [Google Scholar]
  192. Gaillard, C. Un oiseau géant dans les dépôts éocènes du Mont-d’Or lyonnais. Compte Rendus De L’académie Des Sci. 1936, 202, 965–967. [Google Scholar]
  193. Angst, D.; Buffetaut, E.; Lécuyer, C.; Amiot, R. “Terror Birds” (Phorusrhacidae) from the Eocene of Europe imply trans-Tethys dispersal. PLoS ONE 2013, 8, e80357. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  194. Andrews, C.W. On the Pelvis and Hind-limb of Mullerornis betsilei M. Edw. & Grand.; with a Note On the Occurrence of a Ratite Bird in the Upper Eocene Beds of the Fayurn, Egypt. Proc. Zool. Soc. Lond. 1904, 74, 163–171. [Google Scholar]
  195. Rasmussen, D.T.; Simons, E.L.; Hertel, F.; Judd, A. Hindlimb of a giant terrestrial bird from the upper Eocene, Fayum, Egypt. Palaeontology 2001, 44, 325–337. [Google Scholar] [CrossRef]
  196. Pickford, M.; Senut, B. Miocene Palaeobiology of the Orange River Valley, Namibia. Mem. Geol. Surv. Namib. 2003, 19, 1–22. [Google Scholar]
  197. Mourer-Chauviré, C.; Senut, B.; Pickford, M.; Mein, P. The oldest representative of the genus Struthio (Aves: Struthionidae), Struthio coppensi n. sp., from the Lower Miocene of Namibia. Comptes Rendus De L’académie Des Sci. Sér. 2 Fasc. A Sci. De La Terre Des Planètes 1996, 322, 325–332. [Google Scholar]
  198. Mourer-Chauviré, C. Birds (Aves) from the Early Miocene of the Northern Sperrgebiet, Namibia. Mem. Geol. Surv. Namib. 2009, 20, 147–167. [Google Scholar]
  199. Pickford, M. Preliminary Miocene mammalian biostratigraphy for western Kenya. J. Hum. Evol. 1981, 10, 73–97. [Google Scholar] [CrossRef]
  200. Leonard, L.M.; Dyke, G.J.; Walker, C.A. New specimens of a fossil ostrich from the Miocene of Kenya. J. Afr. Earth Sci. 2006, 45, 391–394. [Google Scholar] [CrossRef]
  201. Werdelin, L. Chronology of Neogene mammal localities. In Cenozoic Mammals of Africa; Werdelin, L., Sanders, W.J., Eds.; University of California Press: Berkeley, CA, USA, 2010; pp. 27–43. [Google Scholar]
  202. Rich, P.V. A fossil avifauna from the Upper Miocene Beglia Formation of Tunisia. Notes De Serv. Géologique Du Tunis 1972, 35, 29–66. [Google Scholar]
  203. Roberts, D.L.; Matthews, T.; Herries, A.I.; Boulter, C.; Scott, L.; Dondo, C.; Mtembi, P.; Browning, C.; Smith, R.M.; Haarhoff, P. Regional and global context of the Late Cenozoic Langebaanweg (LBW) palaeontological site: West Coast of South Africa. Earth-Sci. Rev. 2011, 106, 191–214. [Google Scholar] [CrossRef]
  204. Rich, P. Preliminary report on the fossil avian remains from late Tertiary sediments at Langebaanweg (Cape Province), South Africa. South. Afr. J. Sci. 1980, 76, 166–170. [Google Scholar]
  205. Manegold, A.; Louchart, A.; Carrier, J.; Elzanowski, A. The early Pliocene avifauna of Langebaanweg (South Africa): A review and update. In Proceedings of the 8th International Meeting of the Society of Avian Paleontology and Evolution, Vienna, Austria, 11–16 June 2012; pp. 135–152. [Google Scholar]
  206. Geraads, D. Carnivores du Pliocène terminal de Ahl al Oughlam (Casablanca, Maroc). Geobios 1997, 30, 127–164. [Google Scholar] [CrossRef]
  207. Mourer-Chauviré, C.; Geraads, D. The Struthionidae and Pelagornithidae (Aves: Struthioniformes, Odontopterygiformes) from the late Pliocene of Ahl al Oughlam, Morocco [Les Struthionidae et les Pelagornithidae (Aves, Struthioniformes et Odontopterygiformes) du Pliocène final d’Ahl al Oughlam, Maroc]. In Proceedings of the 6ème Symposium international de la Society for Avian Paleontology and Evolution (SAPE), Quillan, France, 28 September–3 October 2004; pp. 169–194. [Google Scholar]
  208. Hay, R.L. Geology of the Olduvai Gorge; University of California Press: Berkeley, CA, USA, 1976. [Google Scholar]
  209. Lowe, P.R. XLI.—On Some Struthious Remains:—1. Description of some Pelvic Remains of a large Fossil Ostrich, Struthio oldawayi, sp. n., from the Lower Pleistocene of Oldaway (Tanganyika Territory); 2. Egg-shell Fragments referable to Psammornis and other Struthiones collected by Mr. St. John Philby in Southern Arabia. Ibis 1933, 75, 652–658. [Google Scholar] [CrossRef]
  210. Leakey, L.S.B. Olduvai Gorge. 1951–1961. Vol 1. A Preliminary Report on the Geology and Fauna; Cambridge University Press: Cambridge, UK, 1967. [Google Scholar]
  211. Arambourg, C. Vertébrés villafranchiens d’Afrique du Nord. (Artiodactyles, Carnivores, Primates, Reptiles, Oiseaux); Fondation Singer-Polignac: Paris, France, 1979; p. 141. [Google Scholar]
  212. Becker-Platen, J.D.; Benda, L.; Steffens, P. Litho-und Biostratigraphische Deutung radiometrischer Altersbestimmungen aus dem Jungtertiär der Türkei; Schweizerbart’sche Verlagsbuchhandlung: Sttutgart, Germany, 1977. [Google Scholar]
  213. Sauer, E.G. A Miocene Ostrich from Anatolia. Ibis 1979, 121, 494–501. [Google Scholar] [CrossRef]
  214. Lambrecht, K. Handbuch der Palaeornithologie; Gebrüder Borntraeger: Berlin, Germany, 1933. [Google Scholar]
  215. Louchart, A.; Bibi, F.; Stewart, J.R. The birds of the late Miocene Baynunah Formation, Abu Dhabi Emirate. In Sands of Time: Late Miocene Fossils from the Baynunah Formation, U.A.E.; Bibi, F., Kraatz, B., Beech, M., Hill, A., Eds.; Springer: Berlin/Heidelberg, Germany, 2020. [Google Scholar]
  216. Tugarinov, A.Y. Some data on Pliocene ornithofauna of Siberia. Tr. Paleozoologichaskogo Inst. 1935, 4, 79–85. [Google Scholar]
  217. Deng, T.; Qiu, Z.; Wang, B.; Wang, X.; Hou, S. Late Cenozoic biostratigraphy of the Linxia basin, northwestern China. In Fossil Mammals of Asia; Columbia University Press: New York, NY, USA, 2013; pp. 243–273. [Google Scholar]
  218. Hou, L.; Zhou, Z.; Zhang, F.; Wang, Z. A Miocene ostrich fossil from Gansu Province, northwest China. Chin. Sci. Bull. 2005, 50, 1808–1810. [Google Scholar] [CrossRef]
  219. Kaakinen, A.; Passey, B.H.; Zhang, Z.; Liu, L.; Pesonen, L.J.; Fortelius, M. Stratigraphy and paleoecology of the classical dragon bone localities of Baode County, Shanxi Province. In Fossil Mammals of Asia: Neogene Biostratigraphy and Chronology; Wang, X., Flynn, L.J., Fortelius, M., Eds.; Columbia University Press: New York, NY, USA, 2013; pp. 203–217. [Google Scholar]
  220. Lowe, P.R. Struthious Remains from Northern China and Mongolia: With Descriptions of Struthio wimani, Struthio anderssoni and Struthio mongolicus, Spp. Nov.; Geological Survey of China: Beijing, China, 1931. [Google Scholar]
  221. Sahni, A.; Kumar, G.; Bajpai, S.; Srinivasan, S. Ultrastructure and taxonomy of ostrich eggshells from Upper Palaeolithic sites of India. J. Palaeontol. Soc. India 1989, 34, 91–98. [Google Scholar]
  222. Sahni, A.; Kumar, G.; Srinivasan, S.; Bajpai, S. Review of Late Pleistocene ostriches (Struthio sp.) of India. Man Environ. 1990, 15, 41–47. [Google Scholar]
  223. Stern, L.A.; Johnson, G.D.; Chamberlain, C.P. Carbon isotope signature of environmental change found in fossil ratite eggshells from a South Asian Neogene sequence. Geology 1994, 22, 419–422. [Google Scholar] [CrossRef]
  224. Patnaik, R.; Sahni, A.; Cameron, D.; Pillans, B.; Chatrath, P.; Simons, E.; Williams, M.; Bibi, F. Ostrich-like eggshells from a 10.1 million-yr-old Miocene ape locality, Haritalyangar, Himachal Pradesh, India. Curr. Sci. 2009, 96, 1485–1495. [Google Scholar]
  225. Davies, W. III.—On some Fossil Bird-Remains from the Siwalik Hills in the British Museum. Geol. Mag. 1880, 7, 18–27. [Google Scholar] [CrossRef] [Green Version]
  226. Lydekker, R. Indian Tertiary and post-Tertiary Vertebrata. Siwalik and Narbada bunodont Suina. Mem. Geol. Surv. India Palaeontol. Indica Ser. 10 1884, 3, 35–104. [Google Scholar]
  227. Ginsburg, I.; Heintz, F.; Sen, S. Le gisement pliocène à Mammiferes de Çalta (Ankara, Turquie). Comptes Rendus De L’académie Des Sci. Paris 1974, 278, 2739–2742. [Google Scholar]
  228. Sen, S. La faune de rangeurs pliocènes de Çalta (Ankara, Turqïe). Bull. Du Muséum Mational D’histoire Nat. Ser. 3 Sci. De La Terre 1977, 61, 89–171. [Google Scholar]
  229. Janoo, A.; Sen, S. Pliocene vertebrate locality of Çalta, Ankara, Turkey. 2. Aves: Struthionidae. Geodiversitas 1998, 20, 339–351. [Google Scholar]
  230. Beliaeva, E.I. Catalogue of Tertiary Fossil Sites of Land Mammals in the USSR; American Geological Institute: Alexandria, VA, USA, 1962. [Google Scholar]
  231. Sotnikova, M.; Dodonov, A.; Pen’kov, A. Upper Cenozoic bio-magnetic stratigraphy of Central Asian mammalian localities. Palaeogeogr. Palaeoclimatol. Palaeoecol. 1997, 133, 243–258. [Google Scholar] [CrossRef]
  232. Cai, B.; Zheng, S.; Liddicoat, J.C.; Li, Q. Review of the litho-, bio-, and chronostratigraphy in the Nihewan Basin, Hebei, China. In Fossil Mammals of Asia; Wang, X., Flynn, L.J., Fortelius, M., Eds.; Columbia University Press: New York, NY, USA, 2013; pp. 218–242. [Google Scholar]
  233. Buffetaut, E.; Angst, D. A Giant Ostrich from the Lower Pleistocene Nihewan Formation of North China, with a Review of the Fossil Ostriches of China. Diversity 2021, 13, 47. [Google Scholar] [CrossRef]
  234. Hou, L. Avian fossils of Pleistocene from Zhoukoudian. Mem. Inst. Vertebr. Palaeontol. Palaeoanthropology Acad. Sin. 1993, 19, 165–297. [Google Scholar]
  235. Vangengeim, E.; Tesakov, A.S. Late Miocene Mammal Localities of Eastern Europe and Western Asia. In Fossil Mammals of Asia; Columbia University Press: New York, NY, USA, 2013; pp. 521–537. [Google Scholar]
  236. Kurochkin, E.N.; Lungu, A.N. A new ostrich from the Middle Sarmatian of Moldavia. Paleontol. Zhurnal 1970, 1, 118–123. [Google Scholar]
  237. Solounias, N.; Rivals, F.; Semprebon, G.M. Dietary interpretation and paleoecology of herbivores from Pikermi and Samos (late Miocene of Greece). Paleobiology 2010, 36, 113–136. [Google Scholar] [CrossRef]
  238. Bachmayer, F.; Zapfe, H. Reste von Struthio aus Pikermi. Proc. Acad. Athens 1962, 37, 247–253. [Google Scholar]
  239. Michailidis, D.; Roussiakis, S.; Theodorou, G. Palaeoavian remains from the late Miocene localities of Pikermi, Chomateri and Kerassiá: Palaeoecological implications. In Proceedings of the 9th Congress of the Carpathian-Balkan Geological Association, Thessaloniki, Greece, 23–26 September 2010; pp. 23–26. [Google Scholar]
  240. Koufos, G.D.; Kostopoulos, D.S.; Konidaris, G.E. Palaeontology of the upper Miocene vertebrate localiti of Nikiti (Chalkidiki Peninsula, Macedonia, Greece) Foreword. Geobios 2016, 49, 29–36. [Google Scholar] [CrossRef]
  241. Spassov, N. The Turolian Megafauna of West Bulgaria and the character of the Late Miocene “Pikermian biome”. Boll. Soc. Paleontol. Ital. 2002, 41, 69–82. [Google Scholar]
  242. Boev, Z.; Spassov, N. First record of ostriches (Aves, Struthioniformes, Struthionidae) from the late Miocene of Bulgaria with taxonomic and zoogeographic discussion. Geodiversitas 2009, 31, 493–507. [Google Scholar] [CrossRef]
  243. Aleksejev, A. Animaux Fossiles du Village Novo-Elisavetovka; Zapiski Novorosiyskogo Institute: Odessa, Ukraine, 1915; pp. 273–453. [Google Scholar]
  244. Burchak-Abramovich, N. Fossil ostriches of Caucasus and Southern Ukraine. Tr. Estestvenoritoricheskogo Muzeya Im. G. Zardabi 1953, 7, 1–206. [Google Scholar]
  245. Forsyth Major, C. Sur un gisement d’ossements fossiles dans l’île de Samos, contemporains de l’âge de Pikermi. Comptes Rendus De L’académie Des Sci. Paris 1888, 107, 1178–1181. [Google Scholar]
  246. Tzankov, T.; Spassov, N.; Stoyanov, K. Neogene-Quaternary Paleogeography and Geodynamics of the Region of Middle Struma River Valley (South.-Western Bulgaria); Publishing House of the South-Western University “N. Rilski”: Blagoevgrad, Bulgaria, 2005; p. 199. [Google Scholar]
  247. Spassov, N.; Tzankov, T.; Geraads, D. Late Neogene stratigraphy, biochronology, faunal diversity and environments of South-West Bulgaria (Struma River Valley). Geodiversitas 2006, 28, 477–498. [Google Scholar]
  248. Theodorou, G.; Athanassiou, A.; Roussiakis, S.; Iliopoulos, G. Preliminary remarks on the late Miocene herbivores of Kerassia (Northern Euboea, Greece). Deinsea 2003, 10, 519–530. [Google Scholar]
  249. Kampouridis, P.; Michailidis, D.; Kargopoulos, N.; Roussiakis, S.; Theodorou, G. First description of an ostrich from the late Miocene of Kerassia (Euboea, Greece): Remarks on its cervical anatomy. Hist. Biol. 2020, 33, 1–8. [Google Scholar] [CrossRef]
  250. Burchak-Abramovich, N. New data on the Tertiary ostriches of Southern Ukraine. Priroda 1939, 5, 94–97. [Google Scholar]
  251. Burchak-Abramovich, N.I.; Vekua, A.K. The Fossil Ostrich from Akchagil Layers of Georgia. Acta Zool. Crac. 1971, 16, 1–26. [Google Scholar]
  252. Tesakov, A. Biostratigraphy of Middle Pliocene–Eopleistocene of Eastern Europe (based on small mammals). Trans. Geol. Inst. 2004, 1–247. [Google Scholar]
  253. Tesakov, A.S.; Dodonov, A.E.; Titov, V.V.; Trubikhin, V.M. Plio-Pleistocene geological record and small mammal faunas, eastern shore of the Azov Sea, Southern European Russia. Quat. Int. 2007, 160, 57–69. [Google Scholar] [CrossRef] [Green Version]
  254. Athanassiou, A. A Villafranchian Hipparion-Bearing Mammal Fauna from Sésklo (E. Thessaly, Greece): Implications for the Question of Hippario-Equus Sympatry in Europe. Quaternary 2018, 1, 12. [Google Scholar] [CrossRef] [Green Version]
  255. Ferring, R.; Oms, O.; Agustí, J.; Berna, F.; Nioradze, M.; Shelia, T.; Tappen, M.; Vekua, A.; Zhvania, D.; Lordkipanidze, D. Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85–1.78 Ma. Proc. Natl. Acad. Sci. USA 2011, 108, 10432–10436. [Google Scholar] [CrossRef] [Green Version]
  256. Burchak-Abramovich, N.; Vekua, A. The fossil ostrich Struthio dmanisensis sp. n. from the Lower Pleistocene of eastern Georgia. Acta Zool. Crac. 1990, 33, 121–132. [Google Scholar]
  257. Lopatin, A.V.; Vislobokova, I.A.; Lavrov, A.V.; Startsev, D.B.; Gimranov, D.O.; Zelenkov, N.V.; Maschenko, E.N.; Sotnikova, M.V.; Tarasenko, K.K.; Titov, V.V. The Taurida Cave, a New Locality of Early Pleistocene Vertebrates in Crimea. Dokl. Biol. Sci. 2019, 485, 40–43. [Google Scholar] [CrossRef]
  258. Zelenkov, N.V.; Lavrov, A.V.; Startsev, D.B.; Vislobokova, I.A.; Lopatin, A.V. A giant early Pleistocene bird from eastern Europe: Unexpected component of terrestrial faunas at the time of early Homo arrival. J. Vertebr. Paleontol. 2019, 39, e1605521. [Google Scholar] [CrossRef]
  259. Mayhew, D.F. Revision of the fossil vole assemblage (Mammalia, Rodentia, Arvicolidae) from Pleistocene deposits at Kisláng, Hungary. Palaeontology 2012, 55, 11–29. [Google Scholar] [CrossRef]
  260. Kretzoi, M. Bericht über die Calabrische (Villafranchische) Fauna von Kisláng, Kom. Feyér. Jahresber. Der Ung. Geol. Anst. 1954, 1953, 212–264. [Google Scholar]
  261. Rich, P.V. Significance of the Tertiary avifaunas from Africa (with emphasis on a mid to late Miocene avifauna from southern Tunisia). Ann. Geol. Surv. Egypt 1974, 4, 167–210. [Google Scholar]
  262. Wang, S. Rediscussion in the taxonomic assignment of “Struthio linxiaensis” Hou, et al., 2005. Acta Paleotologica Sin. 2008, 47, 362–368. [Google Scholar]
  263. Milne-Edwards, A. Recherches Anatomiques et Paléontologiques pour Servir à l’histoire des Oiseaux Fossiles de la France, Tome Second; Victor Masson: Paris, France, 1869–1871; Volume 1, p. 632. [Google Scholar]
  264. Mlíkovsky, J.; Chenzychenova, F.; Filippov, A. Quaternary birds of the Baikal region, East Siberia. Acta Soc. Zool. Bohem. 1997, 61, 151–156. [Google Scholar]
  265. Stimpson, C.M.; Lister, A.; Parton, A.; Clark-Balzan, L.; Breeze, P.S.; Drake, N.A.; Groucutt, H.S.; Jennings, R.; Scerri, E.M.L.; White, T.S.; et al. Middle Pleistocene vertebrate fossils from the Nefud Desert, Saudi Arabia: Implications for biogeography and palaeoecology. Quat. Sci. Rev. 2016, 143, 13–36. [Google Scholar] [CrossRef] [Green Version]
  266. Field, D.J.; Lynner, C.; Brown, C.; Darroch, S.A. Skeletal correlates for body mass estimation in modern and fossil flying birds. PLoS ONE 2013, 8, e82000. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  267. Buffetaut, E.; Angst, D. How large was the giant ostrich of China. EVOLUÇÃO Rev. De Geistória E Pré-História 2017, 2, 6–8. [Google Scholar]
  268. Folch, A.; del Hoyo, J.; Christie, D.A.; Collar, N.; Jutglar, F.; Garcia, E.F.J. Lesser Rhea (Rhea pennata), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  269. Kirwan, G.M.; Korthals, A.; Hodes, C.E. Greater Rhea (Rhea americana), version 2.0. Birds World 2021. [Google Scholar] [CrossRef]
  270. Delsuc, F.; Superina, M.; Ferraris, G.; Tilak, M.K.; Douzery, E. Molecular evidence for hybridisation between the two living species of South American ratites: Potential conservation implications. Conserv. Genet. 2007, 8, 503–507. [Google Scholar] [CrossRef] [Green Version]
  271. Miranda-Ribeiro, A. Notas ornithologicas, tinamidae. Rev. Do Mus. Paul. 1938, 23, 667–788. [Google Scholar]
  272. Bertelli, S.; Chiappe, L.M.; Mayr, G. Phylogenetic interrelationships of living and extinct Tinamidae, volant palaeognathous birds from the New World. Zool. J. Linn. Soc. 2014, 172, 145–184. [Google Scholar] [CrossRef]
  273. Rayner, J.M. Form and function in avian flight. In Current Ornithology; Springer: New York, NY, USA, 1988; pp. 1–66. [Google Scholar]
  274. Widrig, K.E.; Watanabe, J.; Bhullar, B.S.; Field, D.J. Three-dimensional atlas of pectoral musculoskeletal anatomy in the extant tinamou Nothoprocta pentlandii (Palaeognathae: Tinamidae). In Proceedings of the The Society of Vertebrate Paleontology 80th Annual Meeting, Virtual, 12–16 October 2020. [Google Scholar]
  275. Alvarenga, H.M. Uma ave ratitae do paleoceno brasileiro: Bacia calcaŕia de itaboraí, estado do Rio de Janeiro, Brasil. Bol. Do Mus. Nacional. Nova Ser. Geol. 1983, 41, 1–8. [Google Scholar]
  276. Woodburne, M.O.; Goin, F.J.; Raigemborn, M.S.; Heizler, M.; Gelfo, J.N.; Oliveira, E.V. Revised timing of the South American early Paleogene land mammal ages. J. South. Am. Earth Sci. 2014, 54, 109–119. [Google Scholar] [CrossRef]
  277. Agnolín, F.L. Unexpected diversity of ratites (Aves, Palaeognathae) in the early Cenozoic of South America: Palaeobiogeographical implications. Alcheringa: An. Australas. J. Palaeontol. 2017, 41, 101–111. [Google Scholar] [CrossRef]
  278. Alvarenga, H. Diogenornis fragilis Alvarenga, 1985, restudied: A South American ratite closely related to Casuariidae. In Proceedings of the 25th International Ornithological Congress, Campos do Jordão, Brazil, 22–28 August 2010. [Google Scholar]
  279. Tambussi, C. The fossil Rheiformes from Argentina. Cour. Forsch. Senckenberg 1995, 181, 121–129. [Google Scholar]
  280. Pascual, R.; Ortiz-Jaureguizar, E. The Gondwanan and South American episodes: Two major and unrelated moments in the history of the South American mammals. J. Mamm. Evol. 2007, 14, 75–137. [Google Scholar] [CrossRef]
  281. Raigemborn, M.S.; Krause, J.M.; Bellosi, E.; Matheos, S.D. Redefinición estratigráfica del grupo Río Chico (Paleógeno Inferior), en el norte de la cuenca del golfo San Jorge, Chubut. Rev. De La Asoc. Geológica Argent. 2010, 67, 239–256. [Google Scholar]
  282. Krause, J.; Bellosi, E. Paleosols from the Koluel Kaike Formation (Lower-Middle Eocene) in the South-central Chubut, Argentina. A preliminary analysis. In Proceedings of the Actas del IV Congreso Latinoamericano de Sedimentología, La Plata, Argentina, 11–24 November 2006; pp. 125–136. [Google Scholar]
  283. Paredes, J.M.; Colombo, F.; Foix, N.; Allard, J.O.; Nillni, A.; Allo, M. Basaltic Explosive Volcanism in a tuff-dominated intraplate setting, Sarmiento formation (Middle Eocene-lower Miocene), Patagonia, Argentina. Lat. Am. J. Sedimentol. Basin Anal. 2008, 15, 77–92. [Google Scholar]
  284. Kramarz, A.; Garrido, A.; Ribeiro, A.; Ortiz, R. Nuevos registros de vertebrados fósiles de la Formación Chichinales, Mioceno Temprano de la provincia de Río Negro, Argentina. Ameghiniana 2004, 41, 53R. [Google Scholar]
  285. Agnolín, F.; Chafrat, P. New fossil bird remains from the Chichinales Formation (Early Miocene) of northern Patagonia, Argentina. Ann. De Paleontol. 2015, 101, 87–94. [Google Scholar] [CrossRef]
  286. Marshall, L.G.; Patterson, B. Geology and Geochronology of the Mammal-Bearing Tertiary of the Valle de Santa María and Río Corral Quemado, Catamarca Province, Argentina; Field Museum of Natural History: Chicago, IL, USA, 1981. [Google Scholar]
  287. Fleagle, J.G.; Perkins, M.E.; Heizler, M.T.; Nash, B.; Bown, T.M.; Tauber, A.A.; Dozo, M.T.; Tejedor, M.F.; Vizcaíno, S.F.; Kay, R.F. Absolute and relative ages of fossil localities in the Santa Cruz and Pinturas Formations. In Early Miocene Paleobiology in Patagonia: High-Latitude Paleocommunities of the Santa Cruz Formation; Vizcaíno, S.F., Kay, R.F., Bargo, M.S., Eds.; Cambridge University Press: Cambridge, UK, 2012; pp. 41–58. [Google Scholar]
  288. Blisniuk, P.M.; Stern, L.A.; Chamberlain, C.P.; Idleman, B.; Zeitler, P.K. Climatic and ecologic changes during Miocene surface uplift in the Southern Patagonian Andes. Earth Planet. Sci. Lett. 2005, 230, 125–142. [Google Scholar] [CrossRef]
  289. Perkins, M.E.; Fleagle, J.G.; Heizler, M.T.; Nash, B.; Bown, T.; Tauber, A.A.; Dozo, M.T. Tephrochronology of the Miocene Santa Cruz and Pinturas Formations, Argentina. In Early Miocene Paleobiology in Patagonia: High-Latitude Paleocommunities of the Santa Cruz Formation; Vizcaíno, S.F., Kay, R.F., Bargo, M.S., Eds.; Cambridge University Press: Cambridge, UK, 2012; pp. 23–40. [Google Scholar]
  290. Cuitiño, J.I.; Fernicola, J.C.; Kohn, M.J.; Trayler, R.; Naipauer, M.; Bargo, M.S.; Kay, R.F.; Vizcaíno, S.F. U-Pb geochronology of the Santa Cruz Formation (early Miocene) at the Río Bote and Río Santa Cruz (southernmost Patagonia, Argentina): Implications for the correlation of fossil vertebrate localities. J. South. Am. Earth Sci. 2016, 70, 198–210. [Google Scholar] [CrossRef] [Green Version]
  291. Ameghino, F. Enumeración de las aves fósiles de la República Argentina. Rev. Argent. De Hist. Nat. 1891, 1, 441–453. [Google Scholar]
  292. Buffetaut, E. Tertiary ground birds from Patagonia (Argentina) in the Tournouër collection of the Muséum National d’Histoire Naturelle, Paris. Bull. De La Soc. Geol. De Fr. 2014, 185, 207–214. [Google Scholar] [CrossRef]
  293. Diederle, J.M.; Noriega, J. New Records Of Birds In The Santa Cruz Formation (Early-Middle Miocene) At The Río Santa Cruz Valley, Patagonia, Argentina. Publicación Electrónica De La Asoc. Paleontológica Argent. 2020, 61, 55–61. [Google Scholar] [CrossRef] [Green Version]
  294. Forasiepi, A.M.; Martinelli, A.G.; de la Fuente, M.; Dieguez, S.; Bond, M. Paleontology and stratigraphy of the Aisol Formation (Neogene), San Rafael, Mendoza. Cenozoic Geol. Cent. Andes Argentina. SCS Publ. Salta 2011, 135–154. [Google Scholar]
  295. Agnolín, F.L.; Noriega, J.I. Una Nueva Especie de Ñandú (Aves: Rheidae) del Mioceno Tardío de la Mesopotamia Argentina. Ameghiniana 2012, 49, 236–246. [Google Scholar] [CrossRef]
  296. Ganduglia, P. Observaciones geológicas en la región de Ingeniero Jacobacci provincia de Río Negro (con énfasis en el Cretácico y Terciario). Bachelor’s Dissertation, Universidad Nacional de Buenos Aires, Buenos Aires, Argentina, 1977. [Google Scholar]
  297. Cione, A.L.; Azpelicueta, M.d.l.M.; Bond, M.; Carlini, A.A.; Casciotta, J.R.; Cozzuol, M.A.; de la Fuente, M.; Gasparini, Z.; Goin, F.J.; Noriega, J. Miocene vertebrates from Entre Ríos province, eastern Argentina. El Neógeno De Argentina. Ser. Correlación Geológica 2000, 14, 191–237. [Google Scholar]
  298. Cerdeño, E.; Montalvo, C. Los Mesotheriinae (Mesotheriidae, Notoungulata) del Mioceno superior de La Pampa, Argentina. Rev. Española De Paleontol. 2001, 16, 63–75. [Google Scholar] [CrossRef]
  299. Verzi, D.; Deschamps, C.; Montalvo, C. Bioestratigrafía y biocronología del Mioceno tardío de Argentina central. Ameghiniana 2004, 41, 21R. [Google Scholar]
  300. Cenizo, M.M.; Tambussi, C.; Montalvo, P.C.I. Late Miocene continental birds from the Cerro Azul Formation in the Pampean region (central-southern Argentina). Alcheringa: An. Australas. J. Palaeontol. 2012, 36, 47–68. [Google Scholar] [CrossRef]
  301. Bossi, G.E.; Muruaga, C.M. Estratigrafía e inversión tectónica del ’rift’ neógeno en el Campo del Arenal, Catamarca, NO Argentina. Andean Geol. 2009, 36, 311–340. [Google Scholar]
  302. Reguero, M.A.; Candela, A.M. Late Cenozoic mammals from the northwest of Argentina. Cenozoic Geol. Cent. Andes Argent. 2011, 458, 411–426. [Google Scholar]
  303. Noriega, J.I.; Jordan, E.A.; Vezzosi, R.I.; Areta, J.I. A new species of Opisthodactylus Ameghino, 1891 (Aves, Rheidae), from the late Miocene of northwestern Argentina, with implications for the paleobiogeography and phylogeny of rheas. J. Vertebr. Paleontol. 2017, 37, e1278005. [Google Scholar] [CrossRef]
  304. Deschamps, C.M.; Vucetich, M.G.; Verzi, D.H.; Olivares, A.I. Biostratigraphy and correlation of the Monte Hermoso Formation (early Pliocene, Argentina): The evidence from caviomorph rodents. J. South. Am. Earth Sci. 2012, 35, 1–9. [Google Scholar] [CrossRef]
  305. Tomassini, R.L.; Montalvo, C.I.; Deschamps, C.M.; Manera, T. Biostratigraphy and biochronology of the Monte Hermoso Formation (early Pliocene) at its type locality, Buenos Aires Province, Argentina. J. South. Am. Earth Sci. 2013, 48, 31–42. [Google Scholar] [CrossRef]
  306. Rovereto, G. Los estratos araucanos y sus fósiles. An. Del Mus. Nac. De Hist. Nat. De Buenos Aires 1914, 25, 1–247. [Google Scholar]
  307. Palazzesi, L.; Barreda, V. Fossil pollen records reveal a late rise of open-habitat ecosystems in Patagonia. Nat. Commun. 2012, 1294, 1–5. [Google Scholar] [CrossRef] [Green Version]
  308. Tambussi, C.P.; Degrange, F.J. South. American and Antarctic Continental Cenozoic Birds: Paleobiogeographic Affinities and Disparities; Springer: Dordrecht, The Netherlands, 2013; p. 113. [Google Scholar]
  309. Picasso, M.B.J.; Mosto, M.C. New insights about Hinasuri nehuensis (Aves, Rheidae, Palaeognathae) from the early Pliocene of Argentina. Alcheringa: An. Australas. J. Palaeontol. 2016, 40, 244–250. [Google Scholar] [CrossRef]
  310. Ameghino, C.; Rusconi, C. Nueva subespecie de avestruz fósil del Plioceno de Buenos Aires. An. De La Soc. Científica Argent. 1932, 114, 38–42. [Google Scholar]
  311. Moreno, F.P.; Mercerat, A. Catálogo de los pájaros fósiles de la República Argentina conservados en el Museo de La Plata. An. Del Mus. De La Plata Paleontol. 1891, 1, 7–71. [Google Scholar]
  312. Picasso, M.B.J.; Mosto, C. The new taxonomic status of Rhea anchorenensis (Ameghino and Rusconi, 1932) (Aves, Palaeognathae) from the Pleistocene of Argentina. Ann. De Paleontol. 2016, 102, 237–241. [Google Scholar] [CrossRef]
  313. Picasso, M.B.J. Diversity of extinct Rheidae (Aves, Palaeognathae): Historical controversies and the new taxonomic status of Rhea pampeana Moreno and Mercerat 1891 from the Pleistocene of Argentina. Hist. Biol. 2016, 28, 1101–1107. [Google Scholar] [CrossRef]
  314. Chiappe, L. Fossil birds from the Miocene Pinturas Formation of southern Argentina. J. Vertebr. Paleontol. 1991, 11, 21A–22A. [Google Scholar]
  315. Bertelli, S.; Chiappe, L.M. Earliest Tinamous (Aves: Palaeognathae) from the Miocene of Argentina and their Phylogenetic Position; Natural History Museum of Los Angeles County: Los Angeles, CA, USA, 2005. [Google Scholar]
  316. Chandler, R. A New Species of Tinamou (Aves: Tinamiformes, Tinamidae) From the Early-Middle Miocene of Argentina. PalArch’s J. Vertebr. Palaeontol. 2012, 9, 1–8. [Google Scholar]
  317. Woodburne, M.O.; Goin, F.J.; Bond, M.; Carlini, A.A.; Gelfo, J.N.; López, G.M.; Iglesias, A.; Zimicz, A.N. Paleogene Land Mammal Faunas of South America; a Response to Global Climatic Changes and Indigenous Floral Diversity. J. Mamm. Evol. 2014, 21, 1–73. [Google Scholar] [CrossRef]
  318. Brodkorb, P. Notes on fossil Tinamous. Auk 1961, 78, 257. [Google Scholar] [CrossRef]
  319. Tonni, E.P. Los Tinamidos Fosiles Argentinos I. El Genero Tinamisornis Rovereto, 1914. Ameghiniana 1977, 14, 224–232. [Google Scholar]
  320. Tambussi, C.; Tonni, E. Un Tinamidae (Aves: Tinamiformes) del Mioceno tardío de La Pampa (República Argentina) y comentarios sobre los tinámidos fósiles argentinos. Rev. De La Asoc. Paleontológica Argent. 1985, 14, 4. [Google Scholar]
  321. Tambussi, C.P. Catalogo Critico De Los Tinamidae (Aves: Tinamiformes) Fosiles De La Republica Argentina. Ameghiniana 1987, 24, 241–244. [Google Scholar]
  322. Tambussi, C.P. Las Aves del Plioceno Tardío-Pleistoceno Temprano de la Provincia de Buenos Aires; Universidad Nacional de La Plata: Buenos Aires, Argentina, 1989. [Google Scholar]
  323. Marshall, L.G.; Berta, A.; Hofstetter, R.; Pascual, R.; Reig, O.; Bombin, M.; Mones, A. Mammals and Stratigraphy: Geochronology of the Continental Mammal-Bearing Quaternary of South America; Laboratoire de paléontologie des vertébrés de l’Ecole pratique des hautes études: Montpellier, France, 1983. [Google Scholar]
  324. Tambussi, C.; Noriega, J. Summary of the avian fossil record from southern South America. Muenchner Geowiss. Abh. 1996, 30, 245–264. [Google Scholar]
  325. Gill, F.; Donsker, D.; Rasmussen, P. IOC World Bird List. 2021. Available online: (accessed on 30 December 2021).
  326. Parker, S.A. The extinct Kangaroo Island Emu, a hitherto-unrecognised species. Bull. Br. Ornithol. Club 1984, 104, 19–22. [Google Scholar]
  327. Spencer, B. The King Island Emu. Vic. Nat. 1906, 23, 140. [Google Scholar]
  328. Le Souëf, W.H.D. Dromaeus diemenensis. Bull. Br. Ornithol. Club 1907, 21, 13. [Google Scholar]
  329. Heupink, T.H.; Huynen, L.; Lambert, D.M. Ancient DNA Suggests Dwarf and ‘Giant’ Emu Are Conspecific. PLoS ONE 2011, 6, e18728. [Google Scholar] [CrossRef] [Green Version]
  330. Thomson, V.A.; Mitchell, K.J.; Eberhard, R.; Dortch, J.; Austin, J.J.; Cooper, A. Genetic diversity and drivers of dwarfism in extinct island emu populations. Biol. Lett. 2018, 14, 20170617. [Google Scholar] [CrossRef] [Green Version]
  331. Worthy, T.H.; Nguyen, J.M.T. An annotated checklist of the fossil birds of Australia. Trans. R. Soc. South. Aust. 2020, 144, 66–108. [Google Scholar] [CrossRef]
  332. Folch, A.; Christie, D.A.; Garcia, E.F.J. Emu (Dromaius novaehollandiae), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  333. Boles, W. A new emu (Dromaiinae) from the Late Oligocene Etadunna Formation. Emu Austral. Ornithol. 2001, 101, 317–321. [Google Scholar] [CrossRef]
  334. Woodburne, M.O.; Macfadden, B.J.; Case, J.A.; Springer, M.S.; Pledge, N.S.; Power, J.D.; Woodburne, J.M.; Springer, K.B. Land mammal biostratigraphy and magnetostratigraphy of the Etadunna Formation (late Oligocene) of South Australia. J. Vertebr. Paleontol. 1994, 13, 483–515. [Google Scholar] [CrossRef]
  335. Megirian, D.; Prideaux, G.J.; Murray, P.F.; Smit, N. An Australian land mammal age biochronological scheme. Paleobiology 2010, 36, 658–671. [Google Scholar] [CrossRef]
  336. Patterson, C.; Rich, P. The fossil history of the emus, Dromaius (Aves: Dromaiinae). Rec. South. Aust. Mus. 1987, 21, 85–117. [Google Scholar]
  337. Boles, W. Revision of Dromaius gidju Patterson and Rich, 1987 from Riversleigh, northwestern Queensland, Australia, with a reassessment of its generic position. Pap. Avian Paleontol. Honor. Pierce Brodkorb 1992, 36, 195–208. [Google Scholar]
  338. Archer, M.; Hand, S.; Godthelp, H.; Creaser, P. Correlation of the Cainozoic sediments of the Riversleigh World Heritage fossil property, Queensland, Australia. Mémoires Et Trav. De L’institut De Montp. 1997, 131–152. [Google Scholar]
  339. Travouillon, K.J.; Archer, M.; Hand, S.J.; Godthelp, H. Multivariate analyses of Cenozoic mammalian faunas from Riversleigh, northwestern Queensland. Alcheringa: An. Australas. J. Palaeontol. 2006, 30, 323–349. [Google Scholar] [CrossRef]
  340. Boles, W. Hindlimb proportions and locomotion of Emuarius gidju (Patterson & Rich, 1987) (Aves: Casuariidae). Mem. Qld. Mus. 1997, 41, 235–240. [Google Scholar]
  341. Worthy, T.H.; Hand, S.J.; Archer, M. Phylogenetic relationships of the Australian Oligo-Miocene ratite Emuarius gidju Casuariidae. Integr. Zool 2014, 9, 148–166. [Google Scholar] [CrossRef]
  342. Woodburne, M.; Tedford, R.; Archer, M.; Turnbull, W.; Plane, M. Biochronology of the continental mammal record of Australia and New Guinea. Spec. Publ. South. Aust. Dep. Mines Energy 1985, 5, 347–363. [Google Scholar]
  343. Rich, P.V. The Dromornithidae, an extinct family of large ground birds endemic to Australia. Bur. Mineral. Resour. Geol. Geophys. (Aust.) Bull. 1979, 184, 1–196. [Google Scholar]
  344. Rich, P.; Van Tets, J. Fossil birds of Australia and New Guinea: Their biogeographic, phylogenetic and biostratigraphic input. In The Fossil Vertebrate Record of Australasia; Rich, P.V., Thompson, E.M., Eds.; Monash University Offset Printing Unit: Melbourne, Australia, 1982; pp. 235–385. [Google Scholar]
  345. Woodburne, M.O. The Alcoota Fauna, Central Australia: An Integrated Palaeontological and Geological Study; Australian Government Public Service: Canberra, Australia, 1967; Volume 87. [Google Scholar]
  346. Stirton, R.A.; Tedford, R.H.; Woodburne, M.O. Australian Tertiary deposits containing terrestrial mammals. Univ. Calif. Publ. Geol. Sci. 1968, 77, 1–30. [Google Scholar]
  347. Woods, J.T. Fossiliferous fluviatile and cave deposits. J. Geol. Soc. Aust. 1960, 7, 393–403. [Google Scholar]
  348. Stirton, R.; Tedford, R.; Miller, A. Cenozoic stratigraphy and vertebrate paleontology of the Tirari Desert, South Australia. Rec. South. Aust. Mus. 1961, 14, 19–61. [Google Scholar]
  349. Miller, A.H. Fossil ratite birds of the late Tertiary of South Australia. Rec. South. Aust. Mus. 1963, 14, 413–420. [Google Scholar]
  350. Hoch, E.; Holm, P. New K/Ar age determinations of the Awe fauna gangue, Papua New Guinea: Consequences for Papuaustralian late Cenozoic biostratigraphy. Mod. Geol. 1986, 10, 181–195. [Google Scholar]
  351. Plane, M. Stratigraphy and vertebrate fauna of the Otibanda formation, New Guinea; Bureau of Mineral Resources, Geology and Geophysics: Canberra, Australia, 1967; p. 64. [Google Scholar]
  352. Miller, A.H. The history and significance of the fossil Casuarius lydekkeri. Rec. Aust. Mus. 1962, 25, 235–238. [Google Scholar] [CrossRef] [Green Version]
  353. Rothschild, L.W.R.B. On the Former and Present Distribution of the So Called Ratitae Or Ostrich-like Birds with Certain Deductions and a Description of a New Form by CW Andrew. In Proceedings of the Fifth International Ornithological Congress, Berlin, Germany, 4 June 1910; pp. 144–169. [Google Scholar]
  354. Williams, P.; McDougall, I.; Powell, J. Aspects of the quaternary geology of the Tari-Koroba area, Papua. J. Geol. Soc. Aust. 1972, 18, 333–347. [Google Scholar] [CrossRef]
  355. Rich, P.V.; Plane, M.; Schroeder, N. A pygmy cassowary (Casuarius lydekkeri) from late Pleistocene bog deposits at Pureni, Papua New Guinea. BMR J. Aust. Geol. Geophys. 1988, 10, 377–389. [Google Scholar]
  356. Vickers-Rich, P.; Rich, T. Wildlife of Gondwana; Indiana University Press: Bloomington, IN, USA, 1993. [Google Scholar]
  357. Martin, H.A. Cenozoic climatic change and the development of the arid vegetation in Australia. J. Arid Environ. 2006, 66, 533–563. [Google Scholar] [CrossRef]
  358. Yates, A.M.; Worthy, T.H. A diminutive species of emu (Casuariidae: Dromaiinae) from the late Miocene of the Northern Territory, Australia. J. Vertebr. Paleontol. 2019, 39, e1665057. [Google Scholar] [CrossRef]
  359. Campbell, K.E.; Marcus, L. The relationship of hindlimb bone dimensions to body weight in birds. Nat. Hist. Mus. Los Angeles Cty. Sci. Ser. 1992, 36, 395–412. [Google Scholar]
  360. Naish, D.; Perron, R. Structure and function of the cassowary’s casque and its implications for cassowary history, biology and evolution. Hist. Biol. 2014, 28, 507–518. [Google Scholar] [CrossRef]
  361. Calder, W.A. The Kiwi. Sci. Am. 1978, 239, 132–143. [Google Scholar] [CrossRef]
  362. Kinsky, F.C. The consistent presence of paired ovaries in the Kiwi (Apteryx) with some discussion of this condition in other birds. J. Für Ornithol. 1971, 112, 334–357. [Google Scholar] [CrossRef]
  363. Folch, A.; Jutglar, F.; Garcia, E.F.J. Little Spotted Kiwi (Apteryx owenii), version 1.0. Birds World 2020. [Google Scholar] [CrossRef]
  364. Weir, J.T.; Haddrath, O.; Robertson, H.A.; Colbourne, R.M.; Baker, A.J. Explosive ice age diversification of kiwi. Proc. Natl. Acad. Sci. USA 2016, 113, E5580–E5587. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  365. Huynen, L.; Suzuki, T.; Ogura, T.; Watanabe, Y.; Millar, C.D.; Hofreiter, M.; Smith, C.; Mirmoeini, S.; Lambert, D.M. Reconstruction and in vivo analysis of the extinct tbx5 gene from ancient wingless moa (Aves: Dinornithiformes). BMC Evol. Biol. 2014, 14, 75. [Google Scholar] [CrossRef] [Green Version]
  366. Bunce, M.; Worthy, T.; Ford, T.; Hoppitt, W.; Willerslev, E.; Drummond, A.; Cooper, A. Extreme reversed sexual size dimorphism in the extinct New Zealand moa Dinornis. Nature 2003, 425, 172–175. [Google Scholar] [CrossRef]
  367. Perry, G.L.W.; Wheeler, A.B.; Wood, J.R.; Wilmshurst, J.M. A high-precision chronology for the rapid extinction of New Zealand moa (Aves, Dinornithiformes). Quat. Sci. Rev. 2014, 105, 126–135. [Google Scholar] [CrossRef]
  368. Greenwood, R.; Atkinson, I. Evolution of divaricating plants in New Zealand in relation to moa browsing. Proc. New Zealand Ecol. Soc. 1977, 24, 21–33. [Google Scholar]
  369. Bond, W.; Silander, J. Springs and wire plants: Anachronistic defences against Madagascar’s extinct elephant birds. Proc. R. Soc. B 2007, 274, 1985–1992. [Google Scholar] [CrossRef] [Green Version]
  370. Wood, J.R.; Richardson, S.J.; McGlone, M.S.; Wilmshurst, J.M. The diets of moa (Aves: Dinornithiformes). New Zealand J. Ecol. 2020, 44, 1–21. [Google Scholar] [CrossRef] [Green Version]
  371. Allentoft, M.; Rawlence, N.J. Moa’s Ark or volant ghosts of Gondwana? Insights from nineteen years of ancient DNA research on the extinct moa (Aves: Dinornithiformes) of New Zealand. Ann. Anat. 2012, 194, 36–51. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  372. Tennyson, A.J.D. The origin and history of New Zealand’s terrestrial vertebrates. New Zealand J. Ecol. 2010, 34, 6–27. [Google Scholar]
  373. Suggate, R.P.; Stevens, G.R.; Te Punga, M.T. The Geology of New Zealand; EC Keating, Government Printer: Wellington, New Zealand, 1978; Volume 2, p. 819. [Google Scholar]
  374. Landis, C.; Campbell, H.; Begg, J.; Mildenhall, D.; Paterson, A.; Trewick, S. The Waipounamu Erosion Surface: Questioning the antiquity of the New Zealand land surface and terrestrial fauna and flora. Geol. Mag. 2008, 145, 173–197. [Google Scholar] [CrossRef] [Green Version]
  375. Waters, J.M.; Craw, D. Goodbye Gondwana? New Zealand biogeography, geology, and the problem of circularity. Syst. Biol. 2006, 55, 351–356. [Google Scholar] [CrossRef] [Green Version]
  376. Trewick, S.A.; Paterson, A.M.; Campbell, H.J. Hello New Zealand. J. Biogeogr. 2007, 34, 1–6. [Google Scholar] [CrossRef]
  377. Cooper, A.; Cooper, R. The Oligocene bottleneck and New Zealand biota: Genetic record of a past environmental crisis. Proc. R. Soc. B 1995, 261, 293–302. [Google Scholar] [CrossRef]
  378. Carr, L.; McLenachan, P.; Waddell, P.; Gemmell, N.; Penny, D. Analyses of the mitochondrial genome of Leiopelma hochstetteri argues against the full drowning of New Zealand. J. Biogeogr. 2015, 42, 1066–1076. [Google Scholar] [CrossRef]
  379. Edgecombe, G.D.; Giribet, G. A New Zealand species of the trans-Tasman centipede order Craterostigmomorpha (Arthropoda: Chilopoda) corroborated by molecular evidence. Invertebr. Syst. 2008, 22, 1–15. [Google Scholar] [CrossRef]
  380. Boyer, S.L.; Giribet, G. Welcome back New Zealand: Regional biogeography and Gondwanan origin of three endemic genera of mite harvestmen (Arachnida, Opiliones, Cyphophthalmi). J. Biogeogr. 2009, 36, 1084–1099. [Google Scholar] [CrossRef]
  381. Buckley, T.R.; Lord, N.; Ramón-Laca, A.; Allwood, J.; Leschen, R. Multiple lineages of hyper-diverse Zopheridae beetles survived the New Zealand Oligocene Drowning. J. Biogeogr. 2020, 47, 927–940. [Google Scholar] [CrossRef]
  382. Wallis, G.P.; Jorge, F. Going under down under? Lineage ages argue for extensive survival of the Oligocene marine transgression on Zealandia. Mol. Ecol. 2018, 27, 4368–4396. [Google Scholar] [CrossRef] [PubMed]
  383. Sharma, P.P.; Wheeler, W.C. Revenant clades in historical biogeography: The geology of New Zealand predisposes endemic clades to root age shifts. J. Biogeogr. 2013, 40, 1609–1618. [Google Scholar] [CrossRef]
  384. Strogen, D.P.; Bland, K.J.; Nicol, A.; King, P.R. Paleogeography of the Taranaki Basin region during the latest Eocene–Early Miocene and implications for the ‘total drowning’ of Zealandia. N. Z. J. Geol. Geophys. 2014, 57, 110–127. [Google Scholar] [CrossRef]
  385. Mildenhall, D.C.; Pocknall, D.T. Miocene-Pleistocene spores and pollen from Central Otago, South Island, New Zealand. New Zealand Geol. Surv. Paleontol. Bull. 1989, 1–128. [Google Scholar]
  386. Pole, M.; Douglas, B. A quantitative palynostratigraphy of the Miocene Manuherikia Group, New Zealand. J. R. Soc. New Zealand 1998, 28, 405–420. [Google Scholar] [CrossRef]
  387. Worthy, T.H.; Worthy, J.P.; Tennyson, A.; Salisbury, S.; Hand, S.; Scofield, R. Miocene fossils show that kiwi (Apteryx, Apterygidae) are probably not phyletic dwarves. In Paleornithological Research 2013—Proceedings of the 8th International Meeting of the Society of Avian Paleontology and Evolution; Natural History Museum: Vienna, Austria, 2013; pp. 63–80. [Google Scholar]
  388. Calder, W.A. Size, Function, and Life History; Harvard University Press: Cambridge, MA, USA, 1984; p. 448. [Google Scholar]
  389. Gould, S.J. Of kiwi eggs and the Liberty Bell. Nat. Hist. 1986, 95, 20–29. [Google Scholar]
  390. Ducatez, S.; Field, D.J. Disentangling the avian altricial-precocial spectrum: Quantitative assessment of developmental mode, phylogenetic signal, and dimensionality. Evolution 2021, 75, 2717–2735. [Google Scholar] [CrossRef]
  391. Worthy, T.H.; Holdaway, R.N. The Lost World of the Moa: Prehistoric Life of New Zealand; Indiana University Press: Bloomington, IN, USA, 2002; p. 718. [Google Scholar]
  392. Tennyson, A.J.D.; Tomotani, B.M. A new fossil species of kiwi (Aves: Apterygidae) from the mid-Pleistocene of New Zealand. Hist. Biol. 2021, 1–9. [Google Scholar] [CrossRef]
  393. Worthy, T. A mid-Pleistocene rail from New Zealand. Alcheringa 1997, 21, 71–78. [Google Scholar] [CrossRef]
  394. Worthy, T.H.; Tennyson, A.J.D.; Jones, C.; McNamara, J.A.; Douglas, B.J. Miocene waterfowl and other birds from central Otago, New Zealand. J. Syst. Palaeontol. 2007, 5, 1–39. [Google Scholar] [CrossRef] [Green Version]
  395. Tennyson, A.; Worthy, T.; Jones, C.M.; Scofield, R.; Hand, S. Moa’s Ark: Miocene fossils reveal the great antiquity of moa (Aves: Dinornithiformes) in Zealandia. In Proceedings of the VII International Meeting of the Society of Avian Paleontology and Evolution, ed. W.E. Boles and T.H. Worth. Rec. Aust. Mus. 2010, 62, 105–114. [Google Scholar] [CrossRef] [Green Version]
  396. Tennyson, A.J.D.; Martinson, P. Extinct birds of New Zealand; Te Papa Press: Wellington, New Zealand, 2006. [Google Scholar]
  397. Worthy, T.H.; Edwards, A.R.; Millener, P.R. The fossil record of moas (Aves: Dinornithiformes) older than the Otira (last) Glaciation. J. R. Soc. New Zealand 1991, 21, 101–118. [Google Scholar] [CrossRef] [Green Version]
  398. Forbes, H. On avian remains found under a lava-flow near Timaru. Trans. Proc. New Zealand Inst. 1891, 23, 366–372. [Google Scholar]
  399. Mathews, W.H.; Curtis, G. Date of the Pliocene-Pleistocene boundary in New Zealand. Nature 1966, 212, 979–980. [Google Scholar] [CrossRef]
  400. Beu, A.; Edwards, A. New Zealand Pleistocene and late Pliocene glacio-eustatic cycles. Palaeogeogr. Palaeoclimatol. Palaeoecol. 1984, 46, 119–142. [Google Scholar] [CrossRef]
  401. Oliver, W.R.B. The Moas of New Zealand and Australia; Dominion Museum: Wellington, New Zealand, 1949. [Google Scholar]
  402. Marshall, P. Occurence of Fossil Moa-bones in the Lower Wanganui Strata. Trans. Proc. New Zealand Inst. 1919, 51, 250–253. [Google Scholar]
  403. Coates, G. The Rise and Fall of the Southern Alps; Canterbury University Press: Christchurch, New Zealand, 2002; p. 80. [Google Scholar]
  404. Dewar, R.E. Extinctions in Madagascar: The loss of the subfossil fauna. In Quaternary Extinctions: A Prehistoric Revolution; Martin, P.S., Klein, R.G., Eds.; The University of Arizona Press: Tuscon, CA, USA, 1984; pp. 574–593. [Google Scholar]
  405. Samonds, K.E.; Godfrey, L.R.; Ali, J.R.; Goodman, S.M.; Vences, M.; Sutherland, M.R.; Irwin, M.T.; Krause, D.W. Spatial and temporal arrival patterns of Madagascar’s vertebrate fauna explained by distance, ocean currents, and ancestor type. Proc. Natl. Acad. Sci. USA 2012, 109, 5352–5357. [Google Scholar] [CrossRef] [Green Version]
  406. Samonds, K.E. Late Pleistocene bat fossils from Anjohibe Cave, northwestern Madagascar. Acta Chiropterologica 2007, 9, 39–65. [Google Scholar] [CrossRef]
  407. Angst, D.; Buffetaut, É. Palaeobiology of Giant Flightless Birds; Elsevier: London, UK, 2017; p. 281. [Google Scholar]
  408. Clarke, S.; Miller, G.; Fogel, M.; Chivas, A.; Murray-Wallace, C. The amino acid and stable isotope biogeochemistry of elephant bird (Aepyornis) eggshells from southern Madagascar. Quat. Sci. Rev. 2006, 25, 2343–2356. [Google Scholar] [CrossRef]
  409. Torres, C.R.; Clarke, J.A. Nocturnal giants: Evolution of the sensory ecology in elephant birds and other palaeognaths inferred from digital brain reconstructions. Proc. R. Soc. B 2018, 285, 20181540. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  410. Dewar, R.E.; Radimilahy, C.; Wright, H.T.; Jacobs, Z.; Kelly, G.O.; Berna, F. Stone tools and foraging in northern Madagascar challenge Holocene extinction models. Proc. Natl. Acad. Sci. USA 2013, 110, 12583–12588. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  411. Hansford, J.; Wright, P.C.; Rasoamiaramanana, A.; Pérez, V.R.; Godfrey, L.R.; Errickson, D.; Thompson, T.; Turvey, S.T. Early Holocene human presence in Madagascar evidenced by exploitation of avian megafauna. Sci. Adv. 2018, 4, eaat6925. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  412. Anderson, A.; Clark, G.; Haberle, S.; Higham, T.; Nowak-Kemp, M.; Prendergast, A.; Radimilahy, C.; Rakotozafy, L.M.; Ramilisonina; Schwenninger, J.L.; et al. New evidence of megafaunal bone damage indicates late colonization of Madagascar. PLoS ONE 2018, 13, e0204368. [Google Scholar] [CrossRef] [PubMed]
  413. Douglass, K.; Hixon, S.; Wright, H.T.; Godfrey, L.R.; Crowley, B.E.; Manjakahery, B.; Rasolondrainy, T.; Crossland, Z.; Radimilahy, C. A critical review of radiocarbon dates clarifies the human settlement of Madagascar. Quat. Sci. Rev. 2019, 221, 105878. [Google Scholar] [CrossRef]
  414. Hixon, S.W.; Douglass, K.G.; Crowley, B.E.; Rakotozafy, L.M.A.; Clark, G.; Anderson, A.; Haberle, S.; Ranaivoarisoa, J.F.; Buckley, M.; Fidiarisoa, S. Late Holocene spread of pastoralism coincides with endemic megafaunal extinction on Madagascar. Proc. R. Soc. B 2021, 288, 20211204. [Google Scholar] [CrossRef]
  415. Goodman, S.M.; Patterson, B.D. Natural Change and Human Impact in Madagascar; Smithsonian Institution Press: Washington, DC, USA, 1997. [Google Scholar]
  416. Crowley, B.E. A refined chronology of prehistoric Madagascar and the demise of the megafauna. Quat. Sci. Rev. 2010, 29, 2591–2603. [Google Scholar] [CrossRef]
  417. Buffetaut, E. Elephant Birds Under the Sun King? Etienne de Flacourt and the Vouron patra. Bol. Do Cent. Port. De Geo-História E Pré-História 2018, 1, 1. [Google Scholar]
  418. Barrett, P. Antarctic palaeoenvironment through Cenozoic times-a review. Terra Antarct. 1996, 3, 103–119. [Google Scholar]
  419. Pross, J.; Contreras, L.; Bijl, P.K.; Greenwood, D.R.; Bohaty, S.M.; Schouten, S.; Bendle, J.A.; Röhl, U.; Tauxe, L.; Raine, J.I.; et al. Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch. Nature 2012, 488, 73–77. [Google Scholar] [CrossRef]
  420. Contreras, L.; Pross, J.; Bijl, P.K.; Koutsodendris, A.; Raine, J.; van de Schootbrugge, I.; Bas Brinkhuis, H. Early to Middle Eocene vegetation dynamics at the Wilkes Land Margin (Antarctica). Rev. Palaeobot. Palynol. 2013, 197, 119–142. [Google Scholar] [CrossRef]
  421. Poole, I.; Hunt, R.J.; Cantrill, D. A Fossil Wood Flora from King George Island: Ecological Implications for an Antarctic Eocene Vegetation. Ann. Bot. 2001, 88, 33–54. [Google Scholar] [CrossRef] [Green Version]
  422. Tambussi, C.; Noriega, J.; Gbzdzicki, A.; Tatur, A.; Reguero, M.; Vizcaíno, S. Ratite bird from the Paleogene La Meseta formation, Seymour Island, Antarctica. Pol. Polar Res. 1994, 15, 15–20. [Google Scholar]
  423. Field, D.J. Preliminary paleoecological insights from the Pliocene avifauna of Kanapoi, Kenya: Implications for the ecology of Australopithecus anamensis. J. Hum. Evol. 2017, 140, 1–10. [Google Scholar] [CrossRef]
  424. Case, J.A.; Woodburne, M.O.; Chaney, D.S. A gigantic phororhacoid(?) bird from Antarctica. J. Paleontol. 1987, 61, 1280–1284. [Google Scholar] [CrossRef]
  425. Alvarenga, H.M.; Höfling, E. Systematic revision of the Phorusrhacidae (Aves: Ralliformes). Papéis Avulsos De Zool. 2003, 43, 55–91. [Google Scholar] [CrossRef] [Green Version]
  426. Chávez, M. Fossil birds of Chile and Antarctic Peninsula. Arq. Do Mus. Nac. Rio De Jan. 2007, 65, 551–572. [Google Scholar]
  427. Tambussi, C.; Acosta Hospitaleche, C. Antarctic birds (Neornithes) during the Cretaceous-Eocene times. Rev. De La Asoc. Geológica Argent. 2007, 62, 604–617. [Google Scholar]
  428. Alvarenga, H.M.F.; Chiappe, L.M.; Bertelli, S. Phorusrhacids: The Terror Birds. In Living Dinosaurs: The Evolutionary History of Modern Birds; Dyke, G., Kaiser, G., Eds.; John Wiley & Sons: Hoboken, NJ, USA, 2011; pp. 187–208. [Google Scholar]
  429. Cenizo, M. Review of the putative Phorusrhacidae from the Cretaceous and Paleogene of Antarctica: New records of ratites and pelagornithid birds. Pol. Polar Res. 2012, 33, 239–258. [Google Scholar] [CrossRef]
  430. Acosta Hospitaleche, C.; Jadwiszczak, P.; Clarke, J.; Cenizo, M. The fossil record of birds from the James Ross Basin, West Antarctica. Adv. Polar Sci. 2019, 30, 251–273. [Google Scholar] [CrossRef]
  431. Pujana, R.R.; Santillana, S.N.; Marenssi, S.A. Conifer fossil woods from the La Meseta Formation (Eocene of Western Antarctica): Evidence of Podocarpaceae-dominated forests. Rev. Palaeobot. Palynol. 2014, 200, 122–137. [Google Scholar] [CrossRef]
  432. Amenábar, C.R.; Montes, M.; Nozal, F.; Santillana, S. Dinoflagellate cysts of the La Meseta Formation (middle to late Eocene), Antarctic Peninsula: Implications for biostratigraphy, palaeoceanography and palaeoenvironment. Geol. Mag. 2020, 157, 351–366. [Google Scholar] [CrossRef]
  433. Tambussi, C.; Noriega, J.; Santillana, S.; Marenssi, S. Falconid bird from the Middle Eocene La Meseta Formation, Seymour Island. West Antarctica. J. Vertebr. Paleontol. 1995, 15, 55A. [Google Scholar]
  434. Cenizo, M.; Noriega, J.I.; Reguero, M.A. A stem falconid bird from the Lower Eocene of Antarctica and the early southern radiation of the falcons. J. Ornithol. 2016, 157, 885–894. [Google Scholar] [CrossRef]
  435. Goin, F.J.; Reguero, M.A.; Pascual, R.; von Koenigswald, W.; Woodburne, M.O.; Case, J.A.; Marenssi, S.A.; Vieytes, C.; Vizcaíno, S.F. First gondwanatherian mammal from Antarctica. Geol. Soc. Lond. Spec. Publ. 2006, 258, 135–144. [Google Scholar] [CrossRef]
  436. Gelfo, J.; Goin, F.; Bauzá, N.; Reguero, M. The fossil record of Antarctic land mammals: Commented review and hypotheses for future research. Adv. Polar Sci. 2019, 30, 274–292. [Google Scholar] [CrossRef]
  437. Woodburne, M.O.; Zinsmeister, W.J. The First Land Mammal from Antarctica and Its Biogeographic Implications. J. Paleontol. 1984, 58, 913–948. [Google Scholar]
  438. Case, J.A.; Woodburne, M.O.; Chaney, D.S. A new genus of polydolopid marsupial from Antarctica. Geol. Soc. Am. Mem. 1988, 169, 505–522. [Google Scholar]
  439. Goin, F.J.; Carlini, A.A. An early Tertiary microbiotheriid marsupial from Antarctica. J. Vertebr. Paleontol. 1995, 15, 205–207. [Google Scholar] [CrossRef]
  440. Goin, F.J.; Case, J.A.; Woodburne, M.O.; Vizcaíno, S.F.; Reguero, M.A. New Discoveries of “Opposum-Like” Marsupials from Antarctica (Seymour Island, Medial Eocene). J. Mamm. Evol. 1999, 6, 335–365. [Google Scholar] [CrossRef]
  441. Bond, M.; Reguero, M.; Vizcaíno, S.; Marenssi, S. A new ‘South American ungulate’ (Mammalia: Litopterna) from the Eocene of the Antarctic Peninsula. Geol. Soc. Lond. Spec. Publ. 2006, 258, 163–176. [Google Scholar] [CrossRef] [Green Version]
  442. Bond, M.; Pascual, R.; Reguero, M.; Santillana, S.; Marenssi, S. Los primeros ungulados extinguidos sudamericanos de la Antártida. Ameghiniana 1990, 16, 240. [Google Scholar]
  443. Bond, M.; Kramarz, A.; Macphee, R.D.E.; Reguero, M. A New Astrapothere (Mammalia, Meridiungulata) from La Meseta Formation, Seymour (Marambio) Island, and a Reassessment of Previous Records of Antarctic Astrapotheres. Am. Mus. Novit. 2011, 2011, 1–16. [Google Scholar] [CrossRef] [Green Version]
  444. Hooker, J.J. An additional record of a placental mammal (Order Astrapotheria) from the Eocene of West Antarctica. Antarct. Sci. 1992, 4, 107–108. [Google Scholar] [CrossRef]
  445. Gelfo, J.N.; López, G.M.; Santillana, S.N. Eocene ungulate mammals from West Antarctica: Implications from their fossil record and a new species. Antarct. Sci. 2017, 29, 445–455. [Google Scholar] [CrossRef] [Green Version]
  446. Vizcaíno, S.F.; Reguero, M.A.; Goin, F.J.; Tambussi, C.P.; Noriega, J.I. Community structure of Eocene terrestrial vertebrates from Antarctic Peninsula. Publicación Electrónica De La Asoc. Paleontológica Argent. 1998, 5. [Google Scholar]
  447. Scher, H.D.; Martin, E.E. Timing and climatic consequences of the opening of Drake Passage. Science 2006, 312, 428–430. [Google Scholar] [CrossRef] [Green Version]
  448. Bijl, P.K.; Bendle, J.A.P.; Bohaty, S.M.; Pross, J.; Schouten, S.; Tauxe, L.; Stickley, C.E.; McKay, R.M.; Röhl, U.; Olney, M.; et al. Eocene cooling linked to early flow across the Tasmanian Gateway. Proc. Natl. Acad. Sci. USA 2013, 110, 9645–9650. [Google Scholar] [CrossRef] [Green Version]
  449. Wang, Z.; Zhang, J.; Xu, X.; Witt, C.; Deng, Y.; Chenc, G.; Meng, G.; Feng, S.; Xu, L.; Szekely, T. Phylogeny and Sex Chromosome Evolution of Palaeognathae. J. Genet. Genom. 2021. [Google Scholar] [CrossRef]
  450. Kimball, R.T.; Wang, N.; Heimer-McGinn, V.; Ferguson, C.; Braun, E.L. Identifying localized biases in large datasets: A case study using the avian tree of life. Mol. Phylogenetics Evol. 2013, 69, 1021–1032. [Google Scholar] [CrossRef]
  451. Field, D.J.; Berv, J.; Hsiang, A.; Lanfear, R.; Landis, M.; Dornburg, A. Timing the Extant Avian Radiation: The Rise of Modern Birds, and the Importance of Modeling Molecular Rate Variation. Bull. Am. Mus. Nat. History 2020, 440. [Google Scholar] [CrossRef]
  452. Berv, J.S.; Field, D.J. Genomic Signature of an Avian Lilliput Effect across the K-Pg Extinction. Syst. Biol. 2017, 67, 1–13. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  453. Beaulieu, J.M.; O’Meara, B.C.; Crane, P.; Donoghue, M.J. Heterogeneous Rates of Molecular Evolution and Diversification Could Explain the Triassic Age Estimate for Angiosperms. Syst. Biol. 2015, 64, 869–878. [Google Scholar] [CrossRef] [PubMed]
  454. Mayr, G.; De Pietri, V.L.; Scofield, R.P.; Worthy, T.H. On the taxonomic composition and phylogenetic affinities of the recently proposed clade Vegaviidae Agnolín et al., 2017—Neornithine birds from the Upper Cretaceous of the Southern Hemisphere. Cretac. Res. 2018, 86, 178–185. [Google Scholar] [CrossRef] [Green Version]
  455. Field, D.J.; Hsiang, A.Y. A North American stem turaco, and the complex biogeographic history of modern birds. BMC Evol. Biol. 2018, 18. [Google Scholar] [CrossRef] [Green Version]
  456. Mayr, G. Old World Fossil Record of Modern-Type Hummingbirds. Science 2004, 304, 861–864. [Google Scholar] [CrossRef] [Green Version]
  457. Mayr, G.; Alvarenga, H.; Mourer-Chauviré, C. Out of Africa: Fossils shed light on the origin of the hoatzin, an iconic Neotropic bird. Naturwissenschaften 2011, 98, 961–966. [Google Scholar] [CrossRef]
  458. Olson, S.L. Evolution of the rails of the South Atlantic islands (Aves: Rallidae). Smithson. Contrib. Zool. 1973, 152, 1–153. [Google Scholar] [CrossRef]
  459. Wright, N.A.; Steadman, D.W.; Witt, C.C. Predictable evolution toward flightlessness in volant island birds. Proc. Natl. Acad. Sci. USA 2016, 113, 4765–4770. [Google Scholar] [CrossRef] [Green Version]
  460. McNab, B.K. Energy Conservation and the Evolution of Flightlessness in Birds. Am. Nat. 1994, 144, 628–642. [Google Scholar] [CrossRef]
  461. Paxinos, E.E.; James, H.F.; Olson, S.L.; Sorenson, M.D.; Jackson, J.; Fleischer, R.C. mtDNA from fossils reveals a radiation of Hawaiian geese recently derived from the Canada goose (Branta canadensis). Proc. Natl. Acad. Sci. USA 2002, 99, 1399–1404. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  462. Black, K.; Archer, M.; Hand, S.; Godthelp, H. The Rise of Australian Marsupials: A Synopsis of Biostratigraphic, Phylogenetic, Palaeoecologic and Palaeobiogeographic Understanding. In Earth and Life: Global Biodiversity, Extinction Intervals and Biogeographic Perturbations Through Time; Talent, J., Mulder, E.F.J.d., Derbyshire, E., Eds.; International Year of Planet Earth; Springer: Berlin/Heidelberg, Germany, 2012; pp. 983–1078. [Google Scholar]
  463. Lyson, T.; Miller, I.; Bercovici, A.; Weissenburger, K.; Fuentes, A.J.; Clyde, W.; Hagadorn, J.W.; Butrim, M.J.; Johnson, K.R.; Fleming, R.; et al. Exceptional continental record of biotic recovery after the Cretaceous Paleogene mass extinction. Science 2019, 366, 977–983. [Google Scholar] [CrossRef] [PubMed]
  464. Van Valkenburgh, B. Major patterns in the history of carnivorous mammals. Annu. Rev. Earth Planet. Sci. 1999, 27, 463–493. [Google Scholar] [CrossRef] [Green Version]
  465. Figueirido, B.; Palmqvist, P.; Pérez-Claros, J.A.; Janis, C.M. Sixty-six million years along the road of mammalian ecomorphological specialization. Proc. Natl. Acad. Sci. USA 2019, 116, 12698–12703. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  466. Maxwell, E.E.; Larsson, H.C.E. Osteology and myology of the wing of the Emu (Dromaius novaehollandiae), and its bearing on the evolution of vestigial structures. J. Morphol. 2007, 268, 423–441. [Google Scholar] [CrossRef] [PubMed]
  467. Hudson, G.; Schreiweis, D.; Wang, S.C.; Lancaster, D. A numerical study of the wing and leg muscles of tinamous (Tinamidae). Northwest. Sci. 1972, 46, 207–255. [Google Scholar]
  468. Suzuki, D.; Chiba, K.; VanBuren, C.S.; Ohashi, T. The Appendicular Anatomy of the Elegant Crested Tinamou (Eudromia elegans); Kitakyushu Museum of Natural History and Human History: Kitakyushu, Japan, 2014. [Google Scholar]
  469. Witmer, L.M. The extant phylogenetic bracket and the importance of reconstructing soft tissues in fossils. Funct. Morphol. Vertebr. Paleontol. 1995, 1, 19–33. [Google Scholar]
  470. Hosner, P.A.; Tobias, J.A.; Braun, E.L.; Kimball, R.T. How do seemingly non-vagile clades accomplish trans-marine dispersal? Trait and dispersal evolution in the landfowl (Aves: Galliformes). Proc. R. Soc. B 2017, 284. [Google Scholar] [CrossRef]
  471. Chiappe, L.M.; Walker, C.A. Skeletal morphology and systematics of the Cretaceous Euenantiornithes (Ornithothoraces: Enantiornithes). In Mesozoic Birds: Above the Heads of Dinosaurs; Chiappe, L.M., Witmer, L.M., Eds.; University of California Press: Berkeley, CA, USA, 2002; pp. 240–267. [Google Scholar]
  472. O’Connor, J.K.; Chiappe, L.M.; Bell, A. Pre-modern birds: Avian divergences in the Mesozoic. In Living Dinosaurs: The Evolutionary History of Modern Birds; Dyke, G., Kaiser, G., Eds.; Wiley-Blackwell: Hoboken, NJ, USA, 2011; pp. 39–114. [Google Scholar]
  473. Chiappe, L.M.; Qingjin, M. Birds of Stone: Chinese Avian Fossils from the Age of Dinosaurs; JHU Press: Baltimore, MD, USA, 2016. [Google Scholar]
  474. Tschudy, R.H.; Pillmore, C.L.; Orth, C.J.; Gilmore, J.S.; Knight, J.D. Disruption of the Terrestrial Plant Ecosystem at the Cretaceous-Tertiary Boundary, Western Interior. Science 1984, 225, 1030–1032. [Google Scholar] [CrossRef]
  475. Vajda, V.; Raine, J.I.; Hollis, C.J. Indication of Global Deforestation at the Cretaceous-Tertiary Boundary by New Zealand Fern Spike. Science 2001, 294, 1700–1702. [Google Scholar] [CrossRef]
  476. Vajda, V.; Bercovici, A. The global vegetation pattern across the Cretaceous–Paleogene mass extinction interval: A template for other extinction events. Glob. Planet. Chang. 2014, 122, 29–49. [Google Scholar] [CrossRef] [Green Version]
  477. Klein, C.G.; Pisani, D.; Field, D.J.; Lakin, R.; Wills, M.A.; Longrich, N.R. Evolution and dispersal of snakes across the Cretaceous-Paleogene mass extinction. Nat. Commun. 2021, 12, 5335. [Google Scholar] [CrossRef] [PubMed]
  478. Hughes, J.J.; Berv, J.S.; Chester, S.G.B.; Sargis, E.J.; Field, D.J. Ecological selectivity and the evolution of mammalian substrate preference across the K-Pg boundary. Ecol. Evol. 2021, 11, 14540–14554. [Google Scholar] [CrossRef] [PubMed]
  479. Anders, E.; Wolbach, W.S.; Gilmour, I. Major wildfires at the Cretaceous-Tertiary boundary. In Global Biomass Burning; Levine, J.S., Ed.; The MIT Press: Cambridge, MA, USA, 1991; pp. 485–492. [Google Scholar]
  480. Robertson, D.S.; Lewis, W.M.; Sheehan, P.M.; Toon, O.B. K-Pg extinction: Reevaluation of the heat-fire hypothesis. J. Geophys. Res. Biogeosci. 2013, 118, 329–336. [Google Scholar] [CrossRef]
  481. Clyde, W.C.; Ramezani, J.; Johnson, K.R.; Bowring, S.A.; Jones, M.M. Direct high-precision U–Pb geochronology of the end-Cretaceous extinction and calibration of Paleocene astronomical timescales. Earth Planet. Sci. Lett. 2016, 452, 272–280. [Google Scholar] [CrossRef] [Green Version]
  482. Johnson, K.R.; Ellis, B. A Tropical Rainforest in Colorado 1.4 Million Years After the Cretaceous-Tertiary Boundary. Science 2002, 296, 2379–2383. [Google Scholar] [CrossRef]
  483. Bell, A.; Chiappe, L.M. A species-level phylogeny of the Cretaceous Hesperornithiformes (Aves: Ornithuromorpha): Implications for body size evolution amongst the earliest diving birds. J. Syst. Palaeontol. 2014, 14, 239–251. [Google Scholar] [CrossRef]
  484. Dumont, M.; Tafforeau, P.; Bertin, T.; Bhullar, B.; Field, D.; Schulp, A.; Strilisky, B.; Thivichon-Prince, B.; Viriot, L.; Louchart, A. Synchrotron imaging of dentition provides insights into the biology of Hesperornis and Ichthyornis, the last toothed birds. BMC Evol. Biol. 2016, 16, 178. [Google Scholar] [CrossRef] [Green Version]
  485. Field, D.J.; Hanson, M.; Burnham, D.; Wilson, L.E.; Super, K.; Ehret, D.; Ebersole, J.A.; Bhullar, B.A.S. Complete Ichthyornis skull illuminates mosaic assembly of the avian head. Nature 2018, 557, 96–100. [Google Scholar] [CrossRef]
  486. Alegret, L.; Thomas, E.; Lohmann, K.C. End-Cretaceous marine mass extinction not caused by productivity collapse. Proc. Natl. Acad. Sci. USA 2012, 109, 728–732. [Google Scholar] [CrossRef] [Green Version]
  487. Gottschaldt, K. Structure and function of avian somatosensory receptors. In Form and Function in Birds; King, A.S., McLelland, J., Eds.; Academic Press: London, UK, 1985; Volume 3, pp. 375–461. [Google Scholar]
  488. Cunningham, S.; Castro, I.; Alley, M. A new prey detection mechanism for kiwi (Apteryx spp.) suggests convergent evolution between paleognathous and neognathous birds. J. Anat. 2007, 211, 493–502. [Google Scholar] [CrossRef] [PubMed]
  489. Crole, M.; Soley, J. Bony Pits in the Ostrich (Struthio camelus) and Emu (Dromaius novaehollandiae) Bill Tip. Anat. Rec. 2017, 300, 1705–1715. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  490. Zelenitsky, D.K.; Therrien, F.; Ridgely, R.C.; McGee, A.R.; Witmer, L.M. Evolution of olfaction in non-avian theropod dinosaurs and birds. Proc. R. Soc. B 2011, 278, 3625–3634. [Google Scholar] [CrossRef] [PubMed] [Green Version]
Figure 1. Comparison of the palate of a palaeognathous and a neognathous bird. (a) Palate of the palaeognathous Emu Dromaius novaehollandiae. The basipterygoid process is elongate, and the pterygoid and palatine are fused (demarcation between them is approximate). (b) Palate of the neognathous Mute Swan Cygnus olor. The pterygoid and palatine are connected by an intrapterygoid joint, and the short basipterygoid processes are mostly obscured by the pterygoids.
Figure 1. Comparison of the palate of a palaeognathous and a neognathous bird. (a) Palate of the palaeognathous Emu Dromaius novaehollandiae. The basipterygoid process is elongate, and the pterygoid and palatine are fused (demarcation between them is approximate). (b) Palate of the neognathous Mute Swan Cygnus olor. The pterygoid and palatine are connected by an intrapterygoid joint, and the short basipterygoid processes are mostly obscured by the pterygoids.
Diversity 14 00105 g001
Figure 2. Comparison of the pelvis of a palaeognathous and a neognathous bird. The ilioischiadic foramen is highlighted in blue. (a) Pelvis of the Little Spotted Kiwi Apteryx owenii. The ilium and ischium are unfused throughout their lengths, leaving the ilioischiadic foramen open. (b) Pelvis of the Mute Swan Cygnus olor. The ilioischiadic foramen is closed due to the fusion of the posterior ilium and ischium.
Figure 2. Comparison of the pelvis of a palaeognathous and a neognathous bird. The ilioischiadic foramen is highlighted in blue. (a) Pelvis of the Little Spotted Kiwi Apteryx owenii. The ilium and ischium are unfused throughout their lengths, leaving the ilioischiadic foramen open. (b) Pelvis of the Mute Swan Cygnus olor. The ilioischiadic foramen is closed due to the fusion of the posterior ilium and ischium.
Diversity 14 00105 g002
Figure 3. Comparison of the shoulder girdle of a flightless palaeognath displaying the fused ‘ratite’ condition, and that of a volant palaeognath in left lateral view. (a) Fused scapulocoracoid of the flightless Greater Rhea Rhea americana. (b) Unfused scapula and coracoid of the volant Andean Tinamou Nothoprocta pentlandii.
Figure 3. Comparison of the shoulder girdle of a flightless palaeognath displaying the fused ‘ratite’ condition, and that of a volant palaeognath in left lateral view. (a) Fused scapulocoracoid of the flightless Greater Rhea Rhea americana. (b) Unfused scapula and coracoid of the volant Andean Tinamou Nothoprocta pentlandii.
Diversity 14 00105 g003
Figure 4. Comparison of the sterna of a flightless palaeognath, the Common Ostrich Struthio camelus and a volant palaeognath, the Andean Tinamou Nothoprocta pentlandii. (a) Sternum of S. camelus in dorsal view. (b) Sternum of S. camelus in left lateral view. A sternal keel is absent. (c) Sternum of N. pentlandii in dorsal view. (d) Sternum of N. pentlandii in left lateral view. A deep sternal keel provides an attachment area for the pectoralis and supracoracoideus muscles.
Figure 4. Comparison of the sterna of a flightless palaeognath, the Common Ostrich Struthio camelus and a volant palaeognath, the Andean Tinamou Nothoprocta pentlandii. (a) Sternum of S. camelus in dorsal view. (b) Sternum of S. camelus in left lateral view. A sternal keel is absent. (c) Sternum of N. pentlandii in dorsal view. (d) Sternum of N. pentlandii in left lateral view. A deep sternal keel provides an attachment area for the pectoralis and supracoracoideus muscles.
Diversity 14 00105 g004
Figure 5. Old and new hypotheses of palaeognath interrelationships. Extinct clades are indicated by †. (a) Ratite monophyly based on the morphological study of Livezey and Zusi [30]. (b) Molecular phylogeny suggesting ratite paraphyly recovered by Mitchell, et al. [45], Grealy, et al. [41], Yonezawa, et al. [49], Urantówka, et al. [46], and Almeida, et al. [42].
Figure 5. Old and new hypotheses of palaeognath interrelationships. Extinct clades are indicated by †. (a) Ratite monophyly based on the morphological study of Livezey and Zusi [30]. (b) Molecular phylogeny suggesting ratite paraphyly recovered by Mitchell, et al. [45], Grealy, et al. [41], Yonezawa, et al. [49], Urantówka, et al. [46], and Almeida, et al. [42].
Diversity 14 00105 g005
Figure 6. Present-day geographic ranges of extant palaeognath subclades. Range of Rheidae in dark blue, Tinamidae in orange, Struthionidae in green, Casuariidae in aqua, and Apterygidae in pink. [10,14,66,67,68].
Figure 6. Present-day geographic ranges of extant palaeognath subclades. Range of Rheidae in dark blue, Tinamidae in orange, Struthionidae in green, Casuariidae in aqua, and Apterygidae in pink. [10,14,66,67,68].
Diversity 14 00105 g006
Figure 7. Geographic distribution of palaeognath fossils illustrated on palaeogeographic globes. (a) Middle Paleocene, late Paleocene, early Eocene, middle Eocene, late Eocene, and late Oligocene. (b) Early Miocene, middle Miocene, late Miocene, early Pliocene, and late Pliocene. Palaeomaps modified from GPlates ( [83,84].
Figure 7. Geographic distribution of palaeognath fossils illustrated on palaeogeographic globes. (a) Middle Paleocene, late Paleocene, early Eocene, middle Eocene, late Eocene, and late Oligocene. (b) Early Miocene, middle Miocene, late Miocene, early Pliocene, and late Pliocene. Palaeomaps modified from GPlates ( [83,84].
Diversity 14 00105 g007aDiversity 14 00105 g007b
Figure 8. Possible relationships of Lithornithidae to the remainder of Palaeognathae. (a) Scenario A shows a monophyletic Lithornithidae, (b) Scenario B shows a paraphyletic Lithornithidae, and (c) Scenario C shows a polyphyletic Lithornithidae.
Figure 8. Possible relationships of Lithornithidae to the remainder of Palaeognathae. (a) Scenario A shows a monophyletic Lithornithidae, (b) Scenario B shows a paraphyletic Lithornithidae, and (c) Scenario C shows a polyphyletic Lithornithidae.
Diversity 14 00105 g008
Figure 9. Relationships within Struthioniformes as hypothesized by Mayr and Zelenkov [6]. “Eogruidae” is here estimated to be a paraphyletic grade of crownward stem struthioniforms, and Geranoididae is tentatively inferred to be a clade of early stem struthioniforms.
Figure 9. Relationships within Struthioniformes as hypothesized by Mayr and Zelenkov [6]. “Eogruidae” is here estimated to be a paraphyletic grade of crownward stem struthioniforms, and Geranoididae is tentatively inferred to be a clade of early stem struthioniforms.
Diversity 14 00105 g009
Figure 10. A summary of recent molecular phylogenetic studies that recover Rheidae as sister to the remaining notopalaeognaths. Extinct clades are indicated by †. (a) Smith, et al. [39] primary concordance and total evidence tree. (b) Prum, et al. [48] concatenated dataset; Kuhl, et al. [54]. (c) Hackett, et al. [36]; Harshman, et al. [37] maximum likelihood and Bayesian tree; Claramunt and Cracraft [55]. (d) Phillips, et al. [44]; Cloutier, et al. [56] concatenated dataset. (e) Mitchell, et al. [45]; Grealy, et al. [41]; Yonezawa, et al. [49], Urantówka, et al. [46], Almeida, et al. [42].
Figure 10. A summary of recent molecular phylogenetic studies that recover Rheidae as sister to the remaining notopalaeognaths. Extinct clades are indicated by †. (a) Smith, et al. [39] primary concordance and total evidence tree. (b) Prum, et al. [48] concatenated dataset; Kuhl, et al. [54]. (c) Hackett, et al. [36]; Harshman, et al. [37] maximum likelihood and Bayesian tree; Claramunt and Cracraft [55]. (d) Phillips, et al. [44]; Cloutier, et al. [56] concatenated dataset. (e) Mitchell, et al. [45]; Grealy, et al. [41]; Yonezawa, et al. [49], Urantówka, et al. [46], Almeida, et al. [42].
Diversity 14 00105 g010
Figure 11. A summary of recent molecular phylogenetic studies that do not recover Rheidae as sister to the remaining notopalaeognaths. Extinct clades are indicated by †. (a) Kimball, et al. [450]. (b) Prum, et al. [48] binned ASTRAL analysis; Reddy, et al. [58]; Sackton, et al. [50]; Feng, et al. [43] maximum likelihood analysis of avian growth hormone gene copies. (c) Haddrath and Baker [38] 10 and 27 gene concatenated dataset, 27 gene consensus tree; Baker, et al. [40]; Cloutier, et al. [56] total evidence consensus tree. (d) Haddrath and Baker [38] 10 gene consensus tree. (e) Smith, et al. [39] maximum likelihood reanalysis of Phillips, et al. [44]; (f) Harshman, et al. [37] maximum parsimony and RY coded maximum likelihood analysis; Wang, et al. [449]; (g) Smith, et al. [39] using 40 loci.
Figure 11. A summary of recent molecular phylogenetic studies that do not recover Rheidae as sister to the remaining notopalaeognaths. Extinct clades are indicated by †. (a) Kimball, et al. [450]. (b) Prum, et al. [48] binned ASTRAL analysis; Reddy, et al. [58]; Sackton, et al. [50]; Feng, et al. [43] maximum likelihood analysis of avian growth hormone gene copies. (c) Haddrath and Baker [38] 10 and 27 gene concatenated dataset, 27 gene consensus tree; Baker, et al. [40]; Cloutier, et al. [56] total evidence consensus tree. (d) Haddrath and Baker [38] 10 gene consensus tree. (e) Smith, et al. [39] maximum likelihood reanalysis of Phillips, et al. [44]; (f) Harshman, et al. [37] maximum parsimony and RY coded maximum likelihood analysis; Wang, et al. [449]; (g) Smith, et al. [39] using 40 loci.
Diversity 14 00105 g011
Table 1. Lithornithid fossil record.
Table 1. Lithornithid fossil record.
ContinentGeological UnitLocationEpochStageAge ReferenceTaxaInstitutionsReference
North AmericaHornerstown FormationNew Jersey, USALate Cretaceous–early PaleoceneMaastrichtian-DanianOlson and Parris [85]; Staron, et al. [86]?PalaeognathaeNJSMParris and Hope [63]
Fort Union FormationPark County, Montana, USAmiddle PaleoceneSelandianLofgren, et al. [87]; Stidham, et al. [88]Lithornis celetiusUSNM, PUHoude [62]
Polecat Bench FormationWyoming, USAmiddle PaleoceneSelandianLofgren, et al. [87]; Stidham, et al. [88]Lithornis celetiusPU, UMHoude [62]
Goler FormationKern County, California, USAmiddle PaleoceneSelandianLofgren, et al. [89]; Albright, et al. [90]; Lofgren, et al. [91]Lithornis sp.RAMStidham, et al. [88]
Willwood Formation, Sand Coulee bedsPark County, Wyoming, USAlate PaleoceneThanetianLofgren, et al. [87]Lithornis promiscuus,
Lithornis plebius
USNM, UM, AMNHHoude [62]
Willwood FormationBasin, Wyoming, USAearly EoceneYpresianLofgren, et al. [87]Lithornis nasi (provisional), Paracathartes howardaeUM, ROM, USNMHoude [62]
Green River Formation, Fossil Butte memberLincoln County, Wyoming, USAearly EoceneYpresianSmith, et al. [92]Calciavis grandei, Pseudocrypturus cercanaxiusAMNH, USNMHoude [62]; Nesbitt and Clarke [64]
Bridger FormationBridger Basin, Wyoming, USAmiddle EoceneYpresian-LutetianMurphey and Evanoff [93]incertae sedisYPMHoude [62]
EuropeHeers Formation, Orp Sand memberMaret, Belgiummiddle PaleoceneSelandianSmith and Smith [94], De Bast, et al. [95]cf. LithornithidaeIRSNBMayr and Smith [96]
Fissure filling of WalbeckHelmstedt, Germanymiddle PaleoceneSelandianAguilar, et al. [97]Fissuravis weigeltiGMHMayr [98]
Tuffeau de Saint-OmerTempleuve, Francelate PaleoceneThanetianSteurbaut [99];
Moreau and Mathis [100]; Smith and Smith [94]
Lithornithidae gen. et sp. indet.IRSNBMayr and Smith [96]
Ølst FormationLimfjord region, Denmarkearly EoceneYpresianHeilmann-Clausen and Schmitz [101]Lithornis nasi, Lithornis vulturinusMGUHBourdon and Lindow [102]
Fur FormationDenmarkearly EoceneYpresianChambers, et al. [103]Lithornis vulturinusDK, MGUHLeonard, et al. [104]; Bourdon and Lindow [102]
London Clay FormationKent, Essex, Sussex, Englandearly EoceneYpresianKing [105]; Ellison, et al. [106]; Friedman, et al. [107]Lithornis vulturinus, Lithornis nasi, ?Lithornis hookeri, Pseudocrypturus cercanaxius (provisional)NHMUK, WN, PUHoude [62]
Messel FormationMessel, Germanymiddle EoceneYpresian-LutetianFranzen and Haubold [108]; Schaal and Ziegler [109]; Lenz, et al. [110]Lithornis sp.SGPIMH, IRSNBMayr [111];
Mayr [112]
Table 2. Fossil record of stem struthioniforms.
Table 2. Fossil record of stem struthioniforms.
ContinentGeological UnitLocationEpochStageAge ReferenceTaxaInstitutionsReference
EuropeChâlons-sur-Vesles FormationCernay and Berru, Marne, Francelate PaleoceneThanetianBuffetaut and Angst [160]Remiornis hebertiMNHNLemoine [144];
Martin [161]; Mayr [76]
Sables de Bracheux FormationRivecourt, Francelate PaleoceneThanetianSmith, et al. [162]Remiornis hebertiMVBuffetaut and de Ploëg [163]
Argiles rutilantes d’Issel et de Saint-PapoulSaint-Papoul, Franceearly EoceneYpresianLaurent, et al. [164]; Danilo, et al. [165]Galligeranoides boriensisMHNTBourdon, et al. [150]; Mayr [148]
Messel FormationMessel,
middle EoceneYpresian-LutetianFranzen and Haubold [108]; Schaal and Ziegler [109]; Lenz, et al. [110]Palaeotis weigeltiHLMDPeters [146]; Houde and Haubold [143]; Mayr [142]
Geiseltal brown coalGeisel Valley lignite pits, Germanymiddle EoceneLutetianFranzen and Haubold [108]Palaeotis weigeltiGMHLambrecht [145]; Houde and Haubold [143]; Mayr [142]; Mayr [148]
unlistedKolkotova Balka, Tiraspol, Moldovalate MioceneTortonian-MessinianZelenkov and Kurochkin [166]Urmiornis ukrainusPINZelenkov and Kurochkin [166]
unlistedHrebeniki, Odessa Oblast, Ukrainelate MioceneTortonian-MessinianZelenkov and Kurochkin [166]Urmiornis ukrainusNNPMZelenkov and Kurochkin [166]
unlistedMorozovka, Odessa Oblast, Ukrainelate MioceneTortonian-MessinianZelenkov and Kurochkin [166]Urmiornis ukrainusNNPMZelenkov and Kurochkin [166]
unlistedArmavir, Krasnodar Krai, Russialate MioceneTortonian-MessinianZelenkov and Kurochkin [166]Urmiornis ukrainusArmavir Regional MuseumZelenkov and Kurochkin [166]
unlistedSamos, Greecelate MioceneTortonianZelenkov, et al. [167]Ampipelargus majoriNHMUKLydekker [168]; Zelenkov, et al. [167]
Triglia FormationKryopigi, Chalkidiki, Greecelate MioceneTortonian-MessinianTsoukala and Bartsiokas [169]; Lazaridis and Tsoukala [170]?Ampipelargus sp.AUGBoev, et al. [171]; Zelenkov, et al. [167]
AsiaIrdin Manha FormationShara Murun region, Inner Mongolia, Chinamiddle EoceneLutetianLi [172]Eogrus aeolaAMNH, PINWetmore [173]; Kurochkin [152]; Zelenkov and Kurochkin [166]
Khaichin FormationOmnogvi Province, Mongoliamiddle EoceneLutetianZelenkov and Kurochkin [166]Eogrus aeolaPINZelenkov and Kurochkin [166]
Obayla FormationKalmakpai River, East Kazakstanlate EocenePriabonianClarke, et al. [156]Eogrus turanicusPINBendukidze [174]; Zelenkov and Kurochkin [166]
unlistedTsagan Khutel, Bayanhongor Province, Mongolialate EocenePriabonianRussell and Zhai [175]Eogrus crudusPINKurochkin [176]; Zelenkov and Kurochkin [166]
unlistedAlag Tsav, Dornogovi Province, Mongolialate EocenePriabonianDashzėvėg [177]; Clarke, et al. [156]Eogruidae incertae sedisIGMClarke, et al. [156]
Kustovskaya FormationEast Kazakstanlate EocenePriabonianMusser, et al. [178]Eogrus sp.PINKozlova [179];
Kurochkin [176]; Musser, et al. [178]
Ergilin Dzo FormationDornogovi Province, Mongolialatest Eocene-earliest OligocenePriabonian-RupelianDashzėvėg [177]Eogrus sp., Ergilornis rapidus, Ergilornis minor, Ergilornis sp., Ergilornithidae incertae sedis, Sonogrus gregalisPINWetmore [173]; Kozlova [179]; Kurochkin [152]; Kurochkin [176]; Zelenkov and Kurochkin [166]; Mayr and Zelenkov [6]
unlistedMynsualmas, Kazakstanearly MioceneAquitanian-BurdigalianKarhu [180]; Zelenkov and Kurochkin [166]Urmiornis brodkorbiPINKarhu [180]; Zelenkov and Kurochkin [166]
Upper Aral FormationAltynshokysu, Kazakstanearly MioceneAquitanian-BurdigalianKarhu [180]; Zelenkov and Kurochkin [166]Urmiornis brodkorbiPINKarhu [180]; Zelenkov and Kurochkin [166]
Tunggur FormationShara Murun region, Inner Mongolia, Chinamiddle MioceneSerravallianWang, et al. [181]Eogrus wetmoreiAMNH[173]; Brodkorb [182]; Cracraft [183]
unlistedSharga, Govi-Altai Province, Mongoliamiddle MioceneSerravallianMusser, et al. [178]Ergilornis sp. Zelenkov, et al. [167]; Musser, et al. [178]
Nagri and Chinji FormationsGilgit-Baltistan, Pakistanlate middle- early late MioceneSerravallian-TortonianBarry, et al. [184]? Urmiornis cracrafti Harrison and Walker [185]; Musser, et al. [178]
unlistedMaragheh, Iranlate MioceneTortonian-MessinianMusser, et al. [178]Urmiornis maraghanusMNHNMecquenem [186]
Lower Pavlodar FormationPavlodar, Kazakstanlate MioceneTortonian-MessinianZelenkov and Kurochkin [166]Urmiornis sp.PINKurochkin [176]; Zelenkov and Kurochkin [166]
Karabulak FormationKalmakpai, Zaisan, East Kazakstanlate MioceneTortonian-MessinianZelenkov and Kurochkin [166]Urmiornis orientalisPINKurochkin [176]; Zelenkov and Kurochkin [166]
Liushu FormationZhuangeji town, Gansu, Chinalate MioceneMessinianFang, et al. [187]Sinoergilornis guanheensisIVPPMusser, et al. [178]
Khirgis-Nur FormationKhirgis-Nur, Sunur Province, Mongolialate MioceneMessinianZelenkov and Kurochkin [166]Urmiornis sp.PINKurochkin [176]; Zelenkov and Kurochkin [166]
Khirgis-Nur FormationChono-Khariakh, Kobdos Province, Mongoliaearly PlioceneZancleanZelenkov and Kurochkin [166]Urmiornis dzabghanensisPINKurochkin [188]; Zelenkov and Kurochkin [166]
Khirgis-Nur FormationDzagso-Khairkhan-Obo, Ubsunur Province, Mongoliaearly PlioceneZancleanZelenkov and Kurochkin [166]Urmiornis dzabghanensisPINKurochkin [188]; Zelenkov and Kurochkin [166]
Table 3. Crown struthionid fossil record.
Table 3. Crown struthionid fossil record.
ContinentGeological UnitLocationEpochStageAge ReferenceTaxaInstitutionsReference
AfricaElisabethfeld siltsNorthern Sperrgebiet, Namibiaearly MioceneAquitanianPickford and Senut [196]Struthio coppensi Mourer-Chauviré, et al. [197]; Mourer-Chauviré [198]
unlistedKadianga West, Kenyamiddle MioceneLanghianPickford [199]Struthio sp.KNMLeonard, et al. [200]
unlistedCentral Nyanza, Kenyamiddle MioceneSerravallianPickford [199]Struthio sp.KNMLeonard, et al. [200]
unlistedNgorora, Kenyamiddle MioceneSerravallianPickford [199]Struthio sp.KNMLeonard, et al. [200]
Beglia FormationBled el Douarah, Tunisialate MioceneTortonianWerdelin [201]Struthio sp. Rich [202]
Varswater FormationLangebaanweg, South Africaearly PlioceneZancleanRoberts, et al. [203]Struthio cf. asiaticus Rich [204]; Manegold, et al. [205], but see Mikhailov and Zelenkov [78]
unlistedAhl al Oughlam, Casablanca, Moroccolate PliocenePiacenzianGeraads [206]Struthio asiaticus Mourer-Chauviré and Geraads [207], but see Mikhailov and Zelenkov [78]
Olduvai seriesOlduvai Gorge Bed I, Tanzaniaearly PliestoceneGelasianHay [208]Struthio oldawayi Lowe [209];
Leakey [210]
unlistedAïn Boucherit, Algeriaearly PleistoceneGelasianWerdelin [201]Struthio barbarus Arambourg [211]; Mikhailov and Zelenkov [78]
AsiaTurgut strataÇandir, Turkeymiddle MioceneLanghianBecker-Platen, et al. [212]Struthio cf. brachydactylusBGRSauer [213]
unlistedMaragha, Iranlate MioceneTortonian Palaeostruthio karatheodoris Mecquenem [189]; Lambrecht [214];
Mikhailov and Zelenkov [78]
Baynunah FormationUnited Arab Emirateslate MioceneTortonian Palaeostruthio karatheodoris Louchart, et al. [215]
unlistedPavlodar, Kazakhstanlate MioceneMessinian (?) Palaeostruthio karatheodoris Tugarinov [216]; Kurochkin [188]; Mikhailov and Zelenkov [78]
Liushu FormationGansu province, Chinalate MioceneTortonian-MessinianDeng, et al. [217]Struthio (Orientornis) linxiaensis Hou, et al. [218]
unlistedBaode county, Chinalate MioceneMessinianKaakinen, et al. [219]Struthio wimani Lowe [220]; Mikhailov and Zelenkov [78]
Dhok Pathan Formation?, Siwalik seriesSiwalik Hills, Indialate Miocene-early PlioceneMessinian-ZancleanSahni, et al. [221]; Sahni, et al. [222];
Stern, et al. [223]; Patnaik, et al. [224]
Struthio asiaticus Davies [225];
Lydekker [226];
Mikhailov and Zelenkov [78]
unlistedÇalta, Ankara, Turkeyearly PlioceneZancleanGinsburg, et al. [227]; Sen [228]; Janoo and Sen [229]Struthio sp. Janoo and Sen [229]
unlistedPavlodar, Kazakhstanearly PlioceneZanclean Struthio chersonensis Beliaeva [230]
upper Issykulian FormationAkterek, Kyrgyzstanlate PliocenePiacenzianSotnikova, et al. [231]Pachystruthio transcaucasius Sotnikova, et al. [231]
Nihewan FormationNihewan Basin, Chinaearly PleistoceneGelasianCai, et al. [232]Pachystruthio indet.MNHNBuffetaut and Angst [233]
unlistedZhoukoudian, Chinamiddle-late PleistoceneCalabrian- Chibanian “Struthio anderssoni” Hou [234]
EuropeunlistedVarnitsa, Moldovalate MioceneTortonianVangengeim and Tesakov [235]Struthio orlovi Kurochkin and Lungu [236]
unlistedPikermi, Greecelate MioceneTortonianSolounias, et al. [237]Palaeostruthio cf. karatheodoris Bachmayer and Zapfe [238]; Michailidis, et al. [239]
Nikiti FormationNikiti, Greecelate MioceneTortonian Palaeostruthio cf. karatheodoris Koufos, et al. [240]
unlistedHadzhidimovo, Bulgarialate MioceneTortonianSpassov [241]Palaeostruthio karatheodorisNMNHSBoev and Spassov [242]
unlistedNovoelizavetovka, Ukrainelate MioceneTortonian- MessinianVangengeim and Tesakov [235]Struthio novorossicusONUAleksejev [243]; Mikhailov and Zelenkov [78]
unlistedKuyal’nik, Ukrainelate MioceneTortonian-Messinian Struthio sp. Burchak-Abramovich [244]; Mikhailov and Zelenkov [78]
unlistedSamos, Greecelate MioceneTortonian-Messinian Palaeostruthio karatheodorisMGLForsyth Major [245]; Mikhailov and Zelenkov [78]
Strumyani Genetic LithocomplexKamimantsi, Bulgarialate MioceneTortonian- MessinianTzankov, et al. [246]; Spassov, et al. [247]Palaeostruthio cf. karatheodorisNMNHSBoev and Spassov [242]
unlistedKerassia, Greecelate MioceneTortonian-MessinianTheodorou, et al. [248]Palaeostruthio karatheodoris Kampouridis, et al. [249]
unlistedGrebeniki, Ukrainelate MioceneTortonianVangengeim and Tesakov [235]Palaeostruthio karatheodoris, Struthio brachydactylus Burchak-Abramovich [250]; Mikhailov and Zelenkov [78]
Odessa CatacombsOdessa, Ukraineearly PlioceneZanclean Struthio sp. “Odessa Ostrich”ONUBurchak-Abramovich [244]; Mikhailov and Zelenkov [78]
unlistedKvabebi, Georgialate PliocenePiacenzian Pachystruthio transcaucasius Burchak-Abramovich and Vekua [251]; Mikhailov and Zelenkov [78]
Khapry FormationLiventzovka, Rostovskaya Oblast, Russiaearly PleistoceneGelasianTesakov [252]; Tesakov, et al. [253]Struthio sp. “Odessa Ostrich” Kurochkin and Lungu [236]
Sésklo basin sedimentary fillSésklo, Thessaly, Greeceearly PleistoceneGelasian Struthio cf. chersonensis Athanassiou [254]
unlistedDmanisi, Georgiaearly PleistoceneGelasianFerring, et al. [255]Pachystruthio dmanisensis Burchak-Abramovich and Vekua [256]; Mikhailov and Zelenkov [78]
Taurida CaveTaurida, Crimeaearly PleistoceneGelasianLopatin, et al. [257]Pachystruthio dmanisensis Lopatin, et al. [257]; Zelenkov, et al. [258]
unlistedKisláng, Hungaryearly-middle PleistoceneGelasian-CalabrianMayhew [259]Pachystruthio pannonicusGMBKretzoi [260]; Mikhailov and Zelenkov [78]
Table 4. Rheid fossil record.
Table 4. Rheid fossil record.
ContinentGeological UnitLocationEpochStageAge ReferenceTaxaInstitutionsReference
South AmericaItaboraí FormationSão José, Brazillate PaleoceneSelandianPascual and Ortiz-Jaureguizar [280]Diogenornis fragilis Alvarenga [275]
Rio Chico FormationChubut province, Argentinalate PaleoceneThanetianRaigemborn, et al. [281]Diogenornis sp., Rheidae indet.MACNTambussi [279]; Agnolín [277]
Koluel Kaike FormationEl Gauchito, Chubut province, Argentinalate PaleoceneThanetianKrause and Bellosi [282]gen. et sp. indet.MLPAgnolín [277]
Sarmiento FormationChubut province, Argentinamiddle Eocene to early MioceneunknownParedes, et al. [283]gen. et sp. Indet.MACNAgnolín [277]
Chichinales FormationRío Negro province, Argentinaearly MioceneBurdigalianKramarz, et al. [284]Opisthodactylus horaciopereziMPCNAgnolín and Chafrat [285]
Santa Cruz FormationSanta Cruz province, Argentinaearly MioceneBurdigalian-LanghianMarshall and Patterson [286]; Fleagle, et al. [287]; Blisniuk, et al. [288]; Perkins, et al. [289]; Cuitiño, et al. [290]Opisthodactylus patagonicusNHMUK, MPM, YPM, MNHNAmeghino [291]; Buffetaut [292]; Diederle and Noriega [293]
Aisol FormationMendoza province, Argentinaearly MioceneBurdigalian-LanghianForasiepi, et al. [294]Pterocnemia cf. mesopotamicaFMNHAgnolín and Noriega [295]
Level 13 of Ganduglia (1977)Río Negro province, Argentinamiddle MioceneLanghianGanduglia [296]gen et sp. indet.MLPAgnolín [277]
Ituzaingó FormationEntre Ríos province, Argentinalate MioceneMessinianCione, et al. [297]Pterocnemia mesopotamica, Pterocnemia sp., Rheidae indet.MACN, MASP, CICYTTPAgnolín and Noriega [295]
Cerro Azul FormationLa Pampa province, Argentinalate MioceneMessinianCerdeño and Montalvo [298]; Verzi, et al. [299]Pterocnemia sp.GHUNLPCenizo, et al. [300]
Andalhuala FormationTucumán province, Argentinalate Miocene-early PlioceneMessinian-ZancleanMarshall and Patterson [286]; Bossi and Muruaga [301]; Reguero and Candela [302]Opisthodactylus kirchneriMUFYCANoriega, et al. [303]
Monte Hermoso FormationBuenos Aires province, Argentinaearly PlioceneZancleanDeschamps, et al. [304]; Tomassini, et al. [305]Heterorhea dabbenei, Hinasuri nehuensisMLPRovereto [306]; Tambussi [279]
Table 5. Tinamid fossil record.
Table 5. Tinamid fossil record.
ContinentGeological UnitLocationEpochStageAge ReferenceTaxaInstitutionsReference
South AmericaPinturas FormationSanta Cruz province, Argentinaearly MioceneBurdigalianFleagle, et al. [287]Tinamidae gen. et sp. indetMACNBertelli and Chiappe [315]
Santa Cruz FormationSanta Cruz province, Argentinaearly MioceneBurdigalianMarshall and Patterson [286]; Fleagle, et al. [287]; Blisniuk, et al. [288]; Perkins, et al. [289]; Cuitiño, et al. [290]Crypturellus reai, Tinamidae gen. et sp. indetMPM, MACN, AMNHBertelli and Chiappe [315]; Chandler [316]
Cerro Azul FormationLa Pampa province, Argentinalate MioceneMessinianCerdeño and Montalvo [298]; Verzi, et al. [299]Eudromia sp., Nothura sp.MLP, GHUNLPCenizo, et al. [300]
Monte Hermoso FormationBuenos Aires province, Argentinaearly PlioceneZancleanDeschamps, et al. [304]; Tomassini, et al. [305]Eudromia olsoni, Eudromia cf. elegans, Roveretornis intermedius, Tinamisornis parvulusMACNBrodkorb [318]; Tambussi and Tonni [320]; Tomassini, et al. [305]
Chapadmalal FormationBuenos Aires province, Argentinalate PlioceneZanclean-PiacenzianMarshall, et al. [323];Deschamps, et al. [304]Eudromia elegans, Eudromia sp., Nothura parvula, Nothura darwiniiMLPTambussi and Noriega [324]; Tambussi and Degrange [308]
Table 6. Casuarid fossil record.
Table 6. Casuarid fossil record.
ContinentGeological UnitLocationEpochStageAge ReferenceTaxaInstitutionsReference
AustraliaEtadunna FormationLake Palankarinna, South Australia, Australialate OligoceneChattianWoodburne, et al. [334]; Megirian, et al. [335]Emuarius guljarubaSAMBoles [333]
Wipajiri FormationEtadunna Station, South Australia, Australialatest Oligocene-early MioceneChattian-AquitanianWoodburne, et al. [334]; Megirian, et al. [335]Emuarius gidjuSAM, AMPatterson and Rich [336]; Boles [337]
Riversleigh faunal zones A-CRiversleigh, Queensland, Australialatest Oligocene-middle MioceneChattian-LanghianArcher, et al. [338]; Travouillon, et al. [339]; Megirian, et al. [335]Emuarius gidjuAM, QMBoles [337]; Boles [340]; Worthy, et al. [341]
Camfield bedsBullock Creek, Northern Territory, Australiamiddle MioceneunknownWoodburne, et al. [342]Dromaius sp. Rich [343]; Rich and Van Tets [344]
Waite FormationAlcoota, Northern Territory, Australialate MioceneunknownRich [343]Dromaius sp.QM, UCMPWoodburne [345]; Stirton, et al. [346]; Rich [343]; Rich and Van Tets [344]
Chinchilla SandsChinchilla, Queensland, Australiaearly PlioceneZancleanRich and Van Tets [344]Dromaius novaehollandiaeQMWoods [347]; Stirton, et al. [346]; Rich and Van Tets [344]
Tirari FormationLake Palankarinna, South Australia, Australialate Pliocene-early PleistocenePiacenzian-GelasianStirton, et al. [348]; Rich and Van Tets [344]Dromaius ocypusUCMPMiller [349]; Rich [343]; Rich and Van Tets [344]
New GuineaOtibanda FormationMorobe, Papua New Guinealate PliocenePiacenzianHoch and Holm [350]Casuarius sp.UCMPPlane [351]; Rich and Van Tets [344]
Cave depositsunknownPleistocene?UnknownLydekker [168]; Miller [352]Casuarius lydekkeriAMLydekker [168]; Rothschild [353]; Miller [352]; Worthy, et al. [341]
Pleistocene swamp depositsPureni, Papua New Guinealate PleistoceneChibanianWilliams, et al. [354]Casuarius lydekkeriCPCRich, et al. [355]
Table 7. Apterygid fossil record.
Table 7. Apterygid fossil record.
ContinentGeological UnitLocationEpochStageAge ReferenceTaxaInstitutionsReference
New ZealandBannockburn FormationOtago, South Island, New Zealandlate early MioceneBurdigalianMildenhall and Pocknall [385]; Pole and Douglas [386]Proapteryx micromerosNMNZWorthy, et al. [387]
Kaimatira PumiceMarton, North Island, New Zealandmiddle PleistoceneCalabrianWorthy [393]Apteryx littoralisNMNZTennyson and Tomotani [392]
Table 8. Dinornithid fossil record.
Table 8. Dinornithid fossil record.
ContinentGeological UnitLocationEpochStageAge ReferenceTaxaInstitutionsReference
New ZealandBannockburn FormationOtago, South Island, New Zealandlate early MioceneBurdigalianMildenhall and Pocknall [385]; Pole and Douglas [386]Dinornithidae indet.NMNZTennyson, et al. [395]
unlistedTimaru, South Island, New Zealandearly PleistoceneGelasianMathews and Curtis [399]Anomalopteryx didiformis Forbes [398]; Worthy, et al. [397]
unlistedHawke’s Bay, North Island, New Zealandearly Pleistocene?Gelasian?Beu and Edwards [400]Eurapteryx curtusAIMWorthy, et al. [397]
unlistedWairapa, North Island, New Zealandearly Pleistocene?Gelasian?Oliver [401];
Beu and Edwards [400]
“Eurapteryx geranoides”NMNZWorthy, et al. [397]
Tewkesbury FormationWanganui, North Island, New Zealandearly PleistoceneCalabrianBeu and Edwards [400]Dinornis novaezealanidae, Emeidae indet.NMNZMarshall [402]; Worthy, et al. [397]
Table 9. Putative Antarctic ratites.
Table 9. Putative Antarctic ratites.
ContinentGeological UnitLocationEpochStageAge ReferenceTaxaInstitutionsReference
AntarcticaLa Meseta FormationSeymour Islandlate EoceneLutetian- PriabonianAmenábar, et al. [432]“ratititae”MLP, UCRTambussi, et al. [422]; Cenizo [429]; Acosta Hospitaleche, et al. [430]
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Widrig, K.; Field, D.J. The Evolution and Fossil Record of Palaeognathous Birds (Neornithes: Palaeognathae). Diversity 2022, 14, 105.

AMA Style

Widrig K, Field DJ. The Evolution and Fossil Record of Palaeognathous Birds (Neornithes: Palaeognathae). Diversity. 2022; 14(2):105.

Chicago/Turabian Style

Widrig, Klara, and Daniel J. Field. 2022. "The Evolution and Fossil Record of Palaeognathous Birds (Neornithes: Palaeognathae)" Diversity 14, no. 2: 105.

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop