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22 pages, 4053 KiB

Open AccessArticle

Evaluation of the Preservation of Chitinozoans in a Case Study of the Katian?—Hirnantian Succession, Eastern Precordillera of Argentina

by Jessica Gómez, Mercedes di Pasquo and Leonardo Silvestri

Foss. Stud. 2024, 2(4), 273-293; https://doi.org/10.3390/fossils2040013 - 25 Oct 2024

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Abstract

The poor preservation state of chitinozoans recovered from samples of the La Pola (Sandbian–Katian) and Don Braulio formations (Hirnantian-Llandovery), after being processed with standard methods, required significant modifications in processing. The sodium hexametaphosphate technique was used to avoid invasive mechanical procedures. Hence, more [...] Read more.

The poor preservation state of chitinozoans recovered from samples of the La Pola (Sandbian–Katian) and Don Braulio formations (Hirnantian-Llandovery), after being processed with standard methods, required significant modifications in processing. The sodium hexametaphosphate technique was used to avoid invasive mechanical procedures. Hence, more complete chitinozoans that preserved original features produced by biological, mechanical, and chemical degradation appeared. The processes that affected the good preservation of the chitinozoan exine are associated with factors inherent to the sedimentary environment, and biological and geological taphonomic effects that occurred in different regions of the Precordillera, added to the important associated tectonic activity. The thermal alteration was also an important factor in the fragile and brittle condition of the organic matter recovered. This transcends the preservation-processing technique relationship to be used. The results obtained from non-standard processing contribute to the paleoenvironmental interpretation of the Pola and Don Braulio successions, which are still widely discussed, and the determination of the most accurate age of the La Pola Formation. The latter will allow us to propose a biostratigraphic correlation between chitinozoan zones and graptolite zones, given the presence of both groups in the succession studied here, and to establish correlations with other successions in the Precordillera and elsewhere. Full article

(This article belongs to the Special Issue Advances in Palaeontology—Feature Papers to Celebrate the Inaugural Issue of Fossil Studies)

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22 pages, 49469 KiB

Open AccessFeature PaperArticle

First Evidence of Reproductive Strategies in Cephalopods Preserved in Phosphate and Siderite Nodules from the Devonian of Uruguay

by Graciela Piñeiro, Magela Rodao and Pablo Núñez Demarco

Foss. Stud. 2024, 2(3), 223-244; https://doi.org/10.3390/fossils2030011 - 13 Sep 2024

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Abstract

Uruguayan ammonoids are preserved in phosphate and siderite nodules found at the basalmost tillite-like conglomerates of the San Gregorio Formation. This lithostratigraphic unit was deposited under glacial conditions and its age (as well as that of the nodules) has been highly debated because [...] Read more.

Uruguayan ammonoids are preserved in phosphate and siderite nodules found at the basalmost tillite-like conglomerates of the San Gregorio Formation. This lithostratigraphic unit was deposited under glacial conditions and its age (as well as that of the nodules) has been highly debated because glaciations were intermittent in Gondwana during the Late Paleozoic. Reef-builder organisms (e.g., Rugosa and Tabulata), goniatite and orthoceratid cephalopods, brachiopods, sponges, actinopterygians and other indeterminate gnatostomes, as well as fragmentary stems and roots of cf. Lycopsida are the most frequent fossils in the nodules. According to new biostratigraphic and paleoclimatic evidence, these taxa are representative of a reefal environment of a preliminary Devonian age including species that are common in the underlying Early Devonian (Emsian) Durazno Group. Among the ammonoid remains, more than 40 clusters of hatchling goniatites were found in the nodules. Each cluster contains a variable number of shells similar in shape to some of the adults also preserved within the nodules, representing a single species preserved at the same developmental stage (3 mm on size average). The strongly packed shells are enveloped by a substance with a different chemical composition and microstructure with respect to that of the nodule matrix, possibly indicating the presence of a gelatinous-like substance reminiscent of that secreted by the females of some extant cuttlefish and octopuses at the time of the egg spawn. Differing from previously described ammonoid accumulations, our clusters are unique in containing individuals of just a single species preserved in the same ontogenetic stage. That allows us to suggest that they represent a mode of reproduction in which hatchlings were morphologically similar to their parents and occupied the same habitat. Our results are thus one of the oldest known records of reproductive strategies in Paleozoic ammonoids and the phosphate and siderite nodules from the San Gregorio Formation are here classified as a new Konservat-Lagerstätte, which is the oldest known for South America. Full article

(This article belongs to the Special Issue Advances in Palaeontology—Feature Papers to Celebrate the Inaugural Issue of Fossil Studies)

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27 pages, 15755 KiB

Open AccessArticle

A Craniometric Analysis of the Subfamily Cervinae (Cervidae, Mammalia)

by Roman Croitor

Foss. Stud. 2024, 2(3), 196-222; https://doi.org/10.3390/fossils2030010 - 9 Sep 2024

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Abstract

This study employs Principal Component Analysis to examine cranial measurements from both extant and fossil specimens spanning 38 species and comprising over 300 individuals within the subfamily Cervinae. Our findings elucidate craniometric distinctions among cervids characterized by varying body sizes and certain evolutionary [...] Read more.

This study employs Principal Component Analysis to examine cranial measurements from both extant and fossil specimens spanning 38 species and comprising over 300 individuals within the subfamily Cervinae. Our findings elucidate craniometric distinctions among cervids characterized by varying body sizes and certain evolutionary adaptations. While our results generally corroborate previous assertions regarding the limited craniometric variability among plesiometacarpal deer, they also unveil specific cranial adaptations within certain genera and species. The Principal Component Analysis of craniometric data revealed that giant and large-sized deer display significantly broader ecomorphological diversity in cranial shape compared to small-sized deer. Secondly, small-sized deer exhibit greater uniformity in their cranial shape, appearing densely clustered on the factorial map. Thus, we conclude that body size imposes ecological constraints, limiting the available niches due to eco-physiological factors. This study demonstrates that endemic insular deer do not evolve consistent craniometric features attributable to insular isolation, while the cranial proportions of medium-to-small-sized deer delineate a ubiquitous morphological archetype characteristic of numerous cervid taxa spanning diverse phylogenetic lineages and sharing comparable body sizes. This group of “Dama-like” deer, characterized by similar body size, metabolic rates, ecological needs, and cranial morphometry, is referred to here as the fundamental eco-physiological type, typical of warm regions within the Palearctic and Oriental biogeographic realms. Full article

(This article belongs to the Special Issue Advances in Palaeontology—Feature Papers to Celebrate the Inaugural Issue of Fossil Studies)

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18 pages, 21597 KiB

Open AccessArticle

Enigmatic Discoid and Elliptical Structures from Brioverian (Ediacaran-Fortunian) Deposits of Brittany (Armorican Massif, NW of France)

by Didier Néraudeau, Marc Poujol, Alfredo Loi and Jules Charrondière

Foss. Stud. 2024, 2(3), 123-140; https://doi.org/10.3390/fossils2030006 - 28 Jun 2024

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Abstract

The Ediacaran–Cambrian deposits of Brittany (Brioverian series) contain both a few isolated pluricentimetric discoid structures, dome-shaped or “donut”-shaped, and a multitude of centimetric to infracentimetric more or less elliptical fossils or pseudofossils. The discoid and elliptical Brioverian structures are compared to similar fossils [...] Read more.

The Ediacaran–Cambrian deposits of Brittany (Brioverian series) contain both a few isolated pluricentimetric discoid structures, dome-shaped or “donut”-shaped, and a multitude of centimetric to infracentimetric more or less elliptical fossils or pseudofossils. The discoid and elliptical Brioverian structures are compared to similar fossils and pseudofossils found worldwide, and interpreted considering both sedimentary and biological hypotheses. This synthesis of more or less enigmatical fossils from the Ediacaran–Fortunian deposits of Brittany completes the previous descriptions of more well-known discoid and elliptical Brioverian structures such as Nimbia-like and Chuaria-like fossils. It provides a better understanding of the diversity of the Brioverian fossils and original sedimentary structures. Full article

(This article belongs to the Special Issue Advances in Palaeontology—Feature Papers to Celebrate the Inaugural Issue of Fossil Studies)

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11 pages, 1420 KiB

Open AccessArticle

The Diet of Metriorhynchus (Thalattosuchia, Metriorhynchidae): Additional Discoveries and Paleoecological Implications

by Stéphane Hua, Jeff Liston and Jérôme Tabouelle

Foss. Stud. 2024, 2(1), 66-76; https://doi.org/10.3390/fossils2010002 - 20 Feb 2024

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Abstract

A new metriorhynchid specimen with stomach contents is described here. Assigned to Metriorhynchus cf. superciliosus., this specimen has a clear longirostrine form as indicated by its gracile and elongated mandibular rami. This is the second example of gastric contents described for Metriorhynchidae. [...] Read more.

A new metriorhynchid specimen with stomach contents is described here. Assigned to Metriorhynchus cf. superciliosus., this specimen has a clear longirostrine form as indicated by its gracile and elongated mandibular rami. This is the second example of gastric contents described for Metriorhynchidae. This specimen’s preservation allows the identification of the gill apparatus remains of Leedsichthys, the giant suspension-feeding osteichthyan from the Jurassic, including its gill rakers. The gastric contents also contain remains of invertebrates. This specimen indicates that Leedsichthys was not the direct prey of these crocodiles but more that its body was scavenged by them. Longirostrine metriorhynchids were piscivorous but also opportunistic and may have had more of a scavenging component in their lifestyle than previously understood, as all discovered fossils point in this direction. Full article

(This article belongs to the Special Issue Advances in Palaeontology—Feature Papers to Celebrate the Inaugural Issue of Fossil Studies)

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65 pages, 31933 KiB

Open AccessFeature PaperArticle

Taxonomic Status of Nanotyrannus lancensis (Dinosauria: Tyrannosauroidea)—A Distinct Taxon of Small-Bodied Tyrannosaur

by Nicholas R. Longrich and Evan T. Saitta

Foss. Stud. 2024, 2(1), 1-65; https://doi.org/10.3390/fossils2010001 - 3 Jan 2024

Cited by 6 | Viewed by 38216

Abstract

Tyrannosaurs are among the most intensively studied and best-known dinosaurs. Despite this, their relationships and systematics are highly controversial. An ongoing debate concerns the validity of Nanotyrannus lancensis, interpreted either as a distinct genus of small-bodied tyrannosaur or a juvenile of Tyrannosaurus [...] Read more.

Tyrannosaurs are among the most intensively studied and best-known dinosaurs. Despite this, their relationships and systematics are highly controversial. An ongoing debate concerns the validity of Nanotyrannus lancensis, interpreted either as a distinct genus of small-bodied tyrannosaur or a juvenile of Tyrannosaurus rex. We examine multiple lines of evidence and show that the evidence strongly supports recognition of Nanotyrannus as a distinct species for the following reasons: 1. High diversity of tyrannosaurs and predatory dinosaurs supports the idea that multiple tyrannosaurids inhabited the late Maastrichtian of Laramidia; 2. Nanotyrannus lacks characters supporting referral to Tyrannosaurus or Tyrannosaurinae but differs from T. rex in >150 morphological characters, while intermediate forms combining the features of Nanotyrannus and T. rex are unknown; 3. Histology shows specimens of Nanotyrannus showing (i) skeletal fusions, (ii) mature skull bone textures, (iii) slow growth rates relative to T. rex, (iv) decelerating growth in their final years of life, and (v) growth curves predicting adult masses of ~1500 kg or less, showing these animals are subadults and young adults, not juvenile Tyrannosaurus; 4. growth series of other tyrannosaurids, including Tarbosaurus and Gorgosaurus, do not show morphological changes proposed for a Nanotyrannus–Tyrannosaurus growth series, and deriving Tyrannosaurus from Nanotyrannus requires several changes inconsistent with known patterns of dinosaur development; 5. Juvenile T. rex exist, showing diagnostic features of Tyrannosaurus; 6. Phylogenetic analysis suggests that Nanotyrannus may lie outside Tyrannosauridae. Tyrannosaur diversity before the K-Pg extinction is higher than previously appreciated. The challenges inherent in diagnosing species based on fossils mean paleontologists may be systematically underestimating the diversity of ancient ecosystems. Full article

(This article belongs to the Special Issue Advances in Palaeontology—Feature Papers to Celebrate the Inaugural Issue of Fossil Studies)

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11 pages, 19732 KiB

Open AccessFeature PaperArticle

The First Dinosaur from the Kingdom of Cambodia: A Sauropod Fibula from the Lower Cretaceous of Koh Kong Province, South-Western Cambodia

by Vanchan Lim, Eric Buffetaut, Haiyan Tong, Lionel Cavin, Kimchhay Pann and Phalline Polypheakdey Ngoeun

Foss. Stud. 2023, 1(1), 49-59; https://doi.org/10.3390/fossils1010006 - 2 Nov 2023

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Abstract

The first discovery of a dinosaur bone from the Kingdom of Cambodia is reported in this paper. It consists of a sauropod fibula from a sandstone layer on Koh Paur island, in Koh Kong province, in south-western Cambodia. The dinosaur-bearing bed belongs to [...] Read more.

The first discovery of a dinosaur bone from the Kingdom of Cambodia is reported in this paper. It consists of a sauropod fibula from a sandstone layer on Koh Paur island, in Koh Kong province, in south-western Cambodia. The dinosaur-bearing bed belongs to the non-marine Grès Supérieurs series and is apparently of Early Cretaceous age. On the basis of various characters, notably the development of the anteromedial crest, the dinosaur fibula from Koh Paur is referred to a euhelopodid titanosauriform. This first dinosaur discovery in Cambodia suggests that the thick non-marine formations which cover vast areas in the south-western part of the country are potentially an important source of continental Mesozoic vertebrates. Full article

(This article belongs to the Special Issue Advances in Palaeontology—Feature Papers to Celebrate the Inaugural Issue of Fossil Studies)

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Review

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13 pages, 1676 KiB

Open AccessReview

The Wasps (Hymenoptera) from Lower Cretaceous Lebanese and Spanish Ambers

by Sergio Álvarez-Parra and Dany Azar

Foss. Stud. 2024, 2(2), 110-122; https://doi.org/10.3390/fossils2020005 - 5 Jun 2024

Cited by 1 | Viewed by 2503

Abstract

Hymenoptera is the fourth-most diverse insect order today, including wasps, bees, bumblebees, and ants. They show a wide panoply of modes of life, such as herbivory, predation, parasitoidism, pollination, and eusociality. This group also includes a great number of extinct species from both [...] Read more.

Hymenoptera is the fourth-most diverse insect order today, including wasps, bees, bumblebees, and ants. They show a wide panoply of modes of life, such as herbivory, predation, parasitoidism, pollination, and eusociality. This group also includes a great number of extinct species from both amber and compression outcrops. Hymenopterans probably originated in the Paleozoic, although their oldest record is from the Middle or Late Triassic, and their diversity expanded since the Cretaceous. Here, we present a review of the Hymenoptera in Lower Cretaceous ambers from Lebanon (Barremian) and Spain (Albian), which is pivotal for the study of hymenopteran evolution. Hymenoptera in Lebanese ambers are represented by 32 species in 22 genera within 15 families, while in Spanish ambers, they correspond to 49 species in 40 genera within 18 families. Most of these species belong to the ‘Parasitica’, and only a few species have been assigned to the Aculeata. The group ‘Symphyta’ is represented by one species in Spanish amber. The paleobiogeography and possible paleobiologies of the species in these ambers are reviewed. Furthermore, checklists for all Hymenoptera species in Lebanese and Spanish ambers are provided. Full article

(This article belongs to the Special Issue Advances in Palaeontology—Feature Papers to Celebrate the Inaugural Issue of Fossil Studies)

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