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17 pages, 5359 KiB

Open AccessArticle

Morphological Disparity of the Humerus in Modern Birds

by Francisco J. Serrano, Mireia Costa-Pérez, Guillermo Navalón and Alberto Martín-Serra

Diversity 2020, 12(5), 173; https://doi.org/10.3390/d12050173 - 28 Apr 2020

Cited by 13 | Viewed by 16362

From a functional standpoint, the humerus is a key element in the skeleton of vertebrates as it is the forelimb’s bone that connects with the pectoral girdle. In most birds, the humerus receives both the forces exerted by the main flight muscles and [...] Read more.

From a functional standpoint, the humerus is a key element in the skeleton of vertebrates as it is the forelimb’s bone that connects with the pectoral girdle. In most birds, the humerus receives both the forces exerted by the main flight muscles and the aerodynamical stresses exerted upon the wing during locomotion. Despite this functional preeminence, broad scale studies of the morphological disparity of the humerus in the crown group of birds (Neornithes) are lacking. Here, we explore the variation in shape of the humeral outline in modern birds and its evolutionary relationship with size and the evolution of different functional regimes, including several flight strategies, wing propelled diving and complete loss of wing locomotory function. Our findings suggest that most neornithines evolved repeatedly towards a general humeral morphology linked with functional advantages related with more efficient flapping. Lineages evolving high-stress locomotion such as hyperaeriality (e.g., swifts), hovering (e.g., hummingbirds) and wing-propelled diving (e.g., penguins) greatly deviate from this general trend, each exploring different morphologies. Secondarily flightless birds deviate to a lesser degree from their parent clades in humeral morphology likely as a result of the release from constraints related with wing-based locomotion. Furthermore, these taxa show a different allometric trend that flighted birds. Our results reveal that the constraints of aerial and aquatic locomotion are main factors shaping the macroevolution of humeral morphology in modern birds. Full article

(This article belongs to the Special Issue Origins of Modern Avian Biodiversity)

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28 pages, 2278 KiB

Open AccessEditor’s ChoiceArticle

Deep-Time Demographic Inference Suggests Ecological Release as Driver of Neoavian Adaptive Radiation

by Peter Houde, Edward L. Braun and Lawrence Zhou

Diversity 2020, 12(4), 164; https://doi.org/10.3390/d12040164 - 23 Apr 2020

Cited by 12 | Viewed by 4493

Abstract

Assessing the applicability of theory to major adaptive radiations in deep time represents an extremely difficult problem in evolutionary biology. Neoaves, which includes 95% of living birds, is believed to have undergone a period of rapid diversification roughly coincident with the Cretaceous–Paleogene ( [...] Read more.

Assessing the applicability of theory to major adaptive radiations in deep time represents an extremely difficult problem in evolutionary biology. Neoaves, which includes 95% of living birds, is believed to have undergone a period of rapid diversification roughly coincident with the Cretaceous–Paleogene (K-Pg) boundary. We investigate whether basal neoavian lineages experienced an ecological release in response to ecological opportunity, as evidenced by density compensation. We estimated effective population sizes (Ne) of basal neoavian lineages by combining coalescent branch lengths (CBLs) and the numbers of generations between successive divergences. We used a modified version of Accurate Species TRee Algorithm (ASTRAL) to estimate CBLs directly from insertion–deletion (indel) data, as well as from gene trees using DNA sequence and/or indel data. We found that some divergences near the K-Pg boundary involved unexpectedly high gene tree discordance relative to the estimated number of generations between speciation events. The simplest explanation for this result is an increase in Ne, despite the caveats discussed herein. It appears that at least some early neoavian lineages, similar to the ancestor of the clade comprising doves, mesites, and sandgrouse, experienced ecological release near the time of the K-Pg mass extinction. Full article

(This article belongs to the Special Issue Origins of Modern Avian Biodiversity)

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12 pages, 1213 KiB

Open AccessArticle

The First Fossil Owl (Aves, Strigiformes) From the Paleogene of Africa

by N. Adam Smith, Thomas A. Stidham and Jonathan S. Mitchell

Diversity 2020, 12(4), 163; https://doi.org/10.3390/d12040163 - 23 Apr 2020

Cited by 3 | Viewed by 6982

Abstract

The relatively extensive fossil record of owls (Aves, Strigiformes) in North America and Europe stands in stark contrast to the paucity of fossil strigiformes from Africa. The first occurrence of a fossil owl from the Paleogene of Africa extends the fossil record of [...] Read more.

The relatively extensive fossil record of owls (Aves, Strigiformes) in North America and Europe stands in stark contrast to the paucity of fossil strigiformes from Africa. The first occurrence of a fossil owl from the Paleogene of Africa extends the fossil record of this clade on that continent by as much as 25 million years, and confirms the presence of large-sized owls in Oligocene continental faunas. The new fossil is tentatively referred to the Selenornithinae, a clade of large owls previously restricted to Europe. This new fossil owl was likely similar in size to the extant Eagle Owls of the genus Bubo, and suggests that the niche of large, volant, terrestrial avian predator, although relatively rare throughout avian evolutionary history, may be an ecological role that was more common among extinct owls than previously recognized. Full article

(This article belongs to the Special Issue Origins of Modern Avian Biodiversity)

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13 pages, 1479 KiB

Open AccessArticle

Evidence for Wide Dispersal in a Stem Galliform Clade from a New Small-Sized Middle Eocene Pangalliform (Aves: Paraortygidae) from the Uinta Basin of Utah (USA)

by Thomas A. Stidham, K.E. Beth Townsend and Patricia A. Holroyd

Diversity 2020, 12(3), 90; https://doi.org/10.3390/d12030090 - 28 Feb 2020

Cited by 7 | Viewed by 5184

Abstract

A new bird coracoid from the Uinta Formation in the Uinta Basin in Utah (USA) records the presence of the only known pangalliform from the middle Eocene of North America, occurring in a >15 million year gap in their history. This fossil represents [...] Read more.

A new bird coracoid from the Uinta Formation in the Uinta Basin in Utah (USA) records the presence of the only known pangalliform from the middle Eocene of North America, occurring in a >15 million year gap in their history. This fossil represents a new taxon, informally termed the Uintan paraortygid, which is also currently the best-supported record of the extinct Paraortygidae in North America (and among the oldest records of the group in the world). The specimen exhibits a derived enlarged procoracoid prominence with a small procoracoid process, and concave elliptical scapular cotyle that are shared with the middle Eocene paraortygids, Xorazmortyx and Scopelortyx; however, the Uintan paraortygid also has a possibly autapomorphic (pneumatic) fossa adjacent to the scapular cotyle. The similarity in body size and morphology among these widely distributed early paraortygids suggests phylogenetic affinity among them. Given their occurrence in the United States, Uzbekistan, and Namibia during the middle Eocene, these birds likely were good fliers with an increased ability to disperse; and probably had a flexible biology or diet allowing them to occupy a diversity of habitats from coasts and forests to semi-arid savannah-like habitats. The problematic early records of Odontophoridae need to be reexamined as potential members of Paraortygidae and associates of these small-bodied taxa. Full article

(This article belongs to the Special Issue Origins of Modern Avian Biodiversity)

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12 pages, 5310 KiB

Open AccessEditor’s ChoiceArticle

First Complete Wing of a Stem Group Sphenisciform from the Paleocene of New Zealand Sheds Light on the Evolution of the Penguin Flipper

by Gerald Mayr, Vanesa L. De Pietri, Leigh Love, Al A. Mannering, Joseph J. Bevitt and R. Paul Scofield

Diversity 2020, 12(2), 46; https://doi.org/10.3390/d12020046 - 26 Jan 2020

Cited by 10 | Viewed by 7655

Abstract

We describe a partial skeleton of a stem group penguin from the Waipara Greensand in New Zealand, which is tentatively assigned to Muriwaimanu tuatahi. The fossil includes the first complete wing of a Paleocene penguin and informs on previously unknown features of [...] Read more.

We describe a partial skeleton of a stem group penguin from the Waipara Greensand in New Zealand, which is tentatively assigned to Muriwaimanu tuatahi. The fossil includes the first complete wing of a Paleocene penguin and informs on previously unknown features of the mandible and tibiotarsus of small-sized Sphenisciformes from the Waipara Greensand. The wing is distinguished by important features from that of all geologically younger Sphenisciformes and documents an early stage in the evolution of wing-propelled diving in penguins. In particular, the wing of the new fossil exhibits a well-developed alular phalanx and the distal phalanges are not flattened. Because the wing phalanges resemble those of volant birds, we consider it likely that the wing feathers remained differentiated into functional categories and were not short and scale-like as they are in extant penguins. Even though the flippers of geologically younger penguins may favor survival in extremely cold climates, they are likely to have been shaped by hydrodynamic demands. Possible selective drivers include a diminished importance of the hindlimbs in subaquatic propulsion, new foraging strategies (the caudal end of the mandible of the new fossil distinctly differs from that of extant penguins), or increased predation by marine mammals. Full article

(This article belongs to the Special Issue Origins of Modern Avian Biodiversity)

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23 pages, 2958 KiB

Open AccessArticle

Beyond Endocasts: Using Predicted Brain-Structure Volumes of Extinct Birds to Assess Neuroanatomical and Behavioral Inferences

by Catherine M. Early, Ryan C. Ridgely and Lawrence M. Witmer

Diversity 2020, 12(1), 34; https://doi.org/10.3390/d12010034 - 17 Jan 2020

Cited by 18 | Viewed by 7594

Abstract

The shape of the brain influences skull morphology in birds, and both traits are driven by phylogenetic and functional constraints. Studies on avian cranial and neuroanatomical evolution are strengthened by data on extinct birds, but complete, 3D-preserved vertebrate brains are not known from [...] Read more.

The shape of the brain influences skull morphology in birds, and both traits are driven by phylogenetic and functional constraints. Studies on avian cranial and neuroanatomical evolution are strengthened by data on extinct birds, but complete, 3D-preserved vertebrate brains are not known from the fossil record, so brain endocasts often serve as proxies. Recent work on extant birds shows that the Wulst and optic lobe faithfully represent the size of their underlying brain structures, both of which are involved in avian visual pathways. The endocasts of seven extinct birds were generated from microCT scans of their skulls to add to an existing sample of endocasts of extant birds, and the surface areas of their Wulsts and optic lobes were measured. A phylogenetic prediction method based on Bayesian inference was used to calculate the volumes of the brain structures of these extinct birds based on the surface areas of their overlying endocast structures. This analysis resulted in hyperpallium volumes of five of these extinct birds and optic tectum volumes of all seven extinct birds. Phylogenetic ANCOVA (phyANCOVA) were performed on regressions of the brain-structure volumes and endocast structure surface areas on various brain size metrics to determine if the relative sizes of these structures in any extinct birds were significantly different from those of the extant birds in the sample. Phylogenetic ANCOVA indicated that no extinct birds studied had relative hyperpallial volumes that were significantly different from the extant sample, nor were any of their optic tecta relatively hypertrophied. The optic tectum of Dinornis robustus was significantly smaller relative to brain size than any of the extant birds in our sample. This study provides an analytical framework for testing the hypotheses of potential functional behavioral capabilities of other extinct birds based on their endocasts. Full article

(This article belongs to the Special Issue Origins of Modern Avian Biodiversity)

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9 pages, 3087 KiB

Open AccessArticle

On the Preservation of the Beak in Confuciusornis (Aves: Pygostylia)

by Amanda Falk, Jingmai O’Connor, Min Wang and Zhonghe Zhou

Diversity 2019, 11(11), 212; https://doi.org/10.3390/d11110212 - 11 Nov 2019

Cited by 8 | Viewed by 5798

Abstract

The Confuciusornithiformes represent the most stem-ward avian occurrence of an edentulous rostrum. Although a keratinous beak is widely considered to have covered the rostrum in confuciusornithiforms, this feature is almost never preserved, having been previously reported only in the holotype of Confuciusornis dui [...] Read more.

The Confuciusornithiformes represent the most stem-ward avian occurrence of an edentulous rostrum. Although a keratinous beak is widely considered to have covered the rostrum in confuciusornithiforms, this feature is almost never preserved, having been previously reported only in the holotype of Confuciusornis dui and the holotype of Eoconfuciusornis zhengi. This strongly contrasts with the widespread preservation of the keratinous sheaths that cover the manual and pedal ungual phalanges. Here, we report on a third occurrence of a preserved rhamphotheca in a specimen of Confuciusornis sanctus. We illuminated the preserved traces using laser-stimulated fluorescence. Similarly to E. zhengi, the rhamphotheca has been preserved only as a two-dimensional trace, whereas ungual sheaths are preserved in three dimensions. In contrast to the traces preserved in C. dui, the rhamphotheca in the discussed specimen of C. sanctus is straight rather than upturned. This hints towards hidden morphological diversity within the thousands of Confuciusornis specimens, in which species may be further differentiated by soft tissue features or behaviors, much like many living birds, that cannot be detected in fossils, even with exceptional preservation. Full article

(This article belongs to the Special Issue Origins of Modern Avian Biodiversity)

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34 pages, 30653 KiB

Open AccessArticle

Total-Evidence Framework Reveals Complex Morphological Evolution in Nightbirds (Strisores)

by Albert Chen, Noor D. White, Roger B.J. Benson, Michael J. Braun and Daniel J. Field

Diversity 2019, 11(9), 143; https://doi.org/10.3390/d11090143 - 23 Aug 2019

Cited by 17 | Viewed by 12095

Abstract

Strisores is a clade of neoavian birds that include diurnal aerial specialists such as swifts and hummingbirds, as well as several predominantly nocturnal lineages such as nightjars and potoos. Despite the use of genome-scale molecular datasets, the phylogenetic interrelationships among major strisorean groups [...] Read more.

Strisores is a clade of neoavian birds that include diurnal aerial specialists such as swifts and hummingbirds, as well as several predominantly nocturnal lineages such as nightjars and potoos. Despite the use of genome-scale molecular datasets, the phylogenetic interrelationships among major strisorean groups remain controversial. Given the availability of next-generation sequence data for Strisores and the clade’s rich fossil record, we reassessed the phylogeny of Strisores by incorporating a large-scale sequence dataset with anatomical data from living and fossil strisoreans within a Bayesian total-evidence framework. Combined analyses of molecular and morphological data resulted in a phylogenetic topology for Strisores that is congruent with the findings of two recent molecular phylogenomic studies, supporting nightjars (Caprimulgidae) as the extant sister group of the remainder of Strisores. This total-evidence framework allowed us to identify morphological synapomorphies for strisorean clades previously recovered using molecular-only datasets. However, a combined analysis of molecular and morphological data highlighted strong signal conflict between sequence and anatomical data in Strisores. Furthermore, simultaneous analysis of molecular and morphological data recovered differing placements for some fossil taxa compared with analyses of morphological data under a molecular scaffold, highlighting the importance of analytical decisions when conducting morphological phylogenetic analyses of taxa with molecular phylogenetic data. We suggest that multiple strisorean lineages have experienced convergent evolution across the skeleton, obfuscating the phylogenetic position of certain fossils, and that many distinctive specializations of strisorean subclades were acquired early in their evolutionary history. Despite this apparent complexity in the evolutionary history of Strisores, our results provide fossil support for aerial foraging as the ancestral ecological strategy of Strisores, as implied by recent phylogenetic topologies derived from molecular data. Full article

(This article belongs to the Special Issue Origins of Modern Avian Biodiversity)

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25 pages, 3774 KiB

Open AccessArticle

New Material of Paleocene-Eocene Pellornis (Aves: Gruiformes) Clarifies the Pattern and Timing of the Extant Gruiform Radiation

by Grace Musser, Daniel T. Ksepka and Daniel J. Field

Diversity 2019, 11(7), 102; https://doi.org/10.3390/d11070102 - 28 Jun 2019

Cited by 16 | Viewed by 6670

Abstract

Pellornis mikkelseni is an early gruiform from the latest Paleocene-earliest Eocene Fur Formation of Denmark. At approximately 54 million years old, it is among the earliest clear records of the Gruiformes. The holotype specimen, and only material thus far recognised, was originally considered [...] Read more.

Pellornis mikkelseni is an early gruiform from the latest Paleocene-earliest Eocene Fur Formation of Denmark. At approximately 54 million years old, it is among the earliest clear records of the Gruiformes. The holotype specimen, and only material thus far recognised, was originally considered to comprise a partial postcranial skeleton. However, additional mechanical preparation of the nodule containing the holotype revealed that the skeleton is nearly complete and includes a well-preserved skull. In addition to extracting new information from the holotype, we identify and describe two additional specimens of P. mikkelseni which reveal further morphological details of the skeleton. Together, these specimens show that P. mikkelseni possessed a schizorhinal skull and shared many features with the well-known Paleogene Messelornithidae (“Messel rails”). To reassess the phylogenetic position of P. mikkelseni, we modified an existing morphological dataset by adding 20 characters, four extant gruiform taxa, six extinct gruiform taxa, and novel scorings based on the holotype and referred specimens. Phylogenetic analyses recover a clade containing P. mikkelseni, Messelornis, Songzia and crown Ralloidea, supporting P. mikkelseni as a crown gruiform. The phylogenetic position of P. mikkelseni illustrates that some recent divergence time analyses have underestimated the age of crown Gruiformes. Our results suggest a Paleocene origin for this important clade, bolstering evidence for a rapid early radiation of Neoaves following the end-Cretaceous mass extinction. Full article

(This article belongs to the Special Issue Origins of Modern Avian Biodiversity)

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