Ben Creisler
Some recent tetrapod-related papers (some with free pdfs):
Leonardo Corecco, Vitor P. Pereira, Marina B. Soares & Cesar L. Schultz (2021)
Geochemical study on fossil vertebrates from some specific Permian and Triassic beds of the Paranà Basin (Brazil): A preliminary approach.
Journal of South American Earth Sciences 103362
doi: https://doi.org/10.1016/j.jsames.2021.103362
https://www.sciencedirect.com/science/article/abs/pii/S0895981121002091
Highlights
Geochemical study on fossil vertebrates from some specific Permian and Triassic beds of the Paranà Basin (Brazil): A preliminary approach.
Journal of South American Earth Sciences 103362
doi: https://doi.org/10.1016/j.jsames.2021.103362
https://www.sciencedirect.com/science/article/abs/pii/S0895981121002091
Highlights
Characterize some specific Permian and Triassic beds of the Paranà Basin (Brazil).
P contents, in fossils, can indicate its preservation degree.
The fossils from Irati Formation are better preserved than those from the other
units.
Geochemical signatures can help in fossil's robbery or illegal transport cases.
Geochemical signatures can help in fossil's robbery or illegal transport cases.
Abstract
Access to the geochemical conditions of paleoenvironments is made through the analysis of the chemical composition of the hydroxyapatite of fossil bones. This is because the bones were able to incorporate chemical elements from adjacent fluids into their pores and channels during the fossil diagenesis process, and as a result, have their original apatite substituted. The main goal of the present study was to seek geochemical signatures in bones and related sedimentary rocks from three well-known fossiliferous units of the Paranà Basin in southern Brazil: Irati Formation, Cisuralian (three bones/rocks sampled); Rio do Rasto Formation, Guadalupian (three bones/rocks sampled) and Santa Maria Supersequence, Late LadinianâEarly Norian (nine bones/rocks sampled). Fossils and rocks were analyzed by ICP-MS. Although the Permian fossil and rock samples (from Irati + Rio do Rasto Formations) have variations among them, some geochemical parameters are common (high BeâCoâCuâZnâYâWâPb contents). This composition differentiates them from the Triassic fossils and rocks (from Santa Maria Supersequence - high contents of VâAsâBa). The P content (essential in apatite) was used to determine the degree of preservation of the studied material. The better-preserved Permian specimen has a mean = 434.19 ratio (P content of fossil bones/P content of rock) and the lowest ratio = 1.87. Within the Triassic specimens, the better preserved has ratio = 205.64 and lowest = 2.24. In Permian specimens, Y shares similar ionic radio with Ca. For Triassic specimens, Y replaces Ca and As either replaces P or is associated with minerals in bone cavities. So, Y and As substitute Ca in the analyzed material. Therefore, the Permian samples are better preserved than the Triassic ones based on their P contents; Y and As can be used as indicators to differentiate Permian fossils (high Y values) from Triassic ones (high As values). These geochemical signatures can help in forensic cases, such as robbery or illegal transport of fossils.
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Free pdf:
Hugo Dutel, Flora GrÃning, Alana C. Sharp, Peter J. Watson, Anthony Herrel, Callum F. Ross, Marc E. H. Jones, Susan E. Evans & Michael J. Fagan (2021)
Comparative cranial biomechanics in two lizard species: impact of variation in cranial design.
Journal of Experimental Biology 224 (5): jeb234831.
DOI: https://doi.org/10.1242/jeb.234831
https://journals.biologists.com/jeb/article/224/5/jeb234831/223396/Comparative-cranial-biomechanics-in-two-lizard
Comparative cranial biomechanics in two lizard species: impact of variation in cranial design.
Journal of Experimental Biology 224 (5): jeb234831.
DOI: https://doi.org/10.1242/jeb.234831
https://journals.biologists.com/jeb/article/224/5/jeb234831/223396/Comparative-cranial-biomechanics-in-two-lizard
Cranial morphology in lepidosaurs is highly disparate and characterised by the frequent loss or reduction of bony elements. In varanids and geckos, the loss of the postorbital bar is associated with changes in skull shape, but the mechanical principles underlying this variation remain poorly understood. Here, we sought to determine how the overall cranial architecture and the presence of the postorbital bar relate to the loading and deformation of the cranial bones during biting in lepidosaurs. Using computer-based simulation techniques, we compared cranial biomechanics in the varanid Varanus niloticus and the teiid Salvator merianae, two large, active foragers. The overall strain magnitude and distribution across the cranium were similar in the two species, despite lower strain gradients in V. niloticus. In S. merianae, the postorbital bar is important for resistance of the cranium to feeding loads. The postorbital ligament, which in varanids partially replaces the postorbital bar, does not affect bone strain. Our results suggest that the reduction of the postorbital bar impaired neither biting performance nor the structural resistance of the cranium to feeding loads in V. niloticus. Differences in bone strain between the two species might reflect demands imposed by feeding and non-feeding functions on cranial shape. Beyond variation in cranial bone strain related to species-specific morphological differences, our results reveal that similar mechanical behaviour is shared by lizards with distinct cranial shapes. Contrary to the situation in mammals, the morphology of the circumorbital region, calvaria and palate appears to be important for withstanding high feeding loads in these lizards.
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Free pdf:
Sandy Momoe Kawano & Richard W. Blob (2021)
Terrestrial force production by the limbs of a semi-aquatic salamander provides insight into the evolution of terrestrial locomotor mechanics.
bioRxiv 2021.05.01.442256 (preprint)
doi: https://doi.org/10.1101/2021.05.01.442256
https://www.biorxiv.org/content/10.1101/2021.05.01.442256v1
Amphibious fishes and salamanders are valuable functional analogs for vertebrates that spanned the water-to-land transition. However, investigations of walking mechanics have focused on terrestrial salamanders and, thus, may better reflect the capabilities of stem tetrapods that were already terrestrial. The earliest tetrapods were aquatic, so salamanders that are not primarily terrestrial may yield more appropriate data for modelling the incipient stages of terrestrial locomotion. In the present study, locomotor biomechanics were quantified from semi-aquatic Pleurodeles waltl, a salamander that spends most of its adult life in water, and then compared to a primarily terrestrial salamander (Ambystoma tigrinum) and semi-aquatic fish (Periophthalmus barbarus) to evaluate whether walking mechanics show greater similarity between species with ecological versus phylogenetic similarities. Ground reaction forces (GRFs) from individual limbs or fins indicated that the pectoral appendages of each taxon had distinct patterns of force production, but hind limb forces were comparable between the salamanders. The rate of force development ('yank') was sometimes slower in P. waltl but generally comparable between the three species. Finally, medial inclination of the GRF in P. waltl was intermediate between semi-aquatic fish and terrestrial salamanders, potentially elevating bone stresses among more aquatic taxa as they move on land. These data provide a framework for modelling stem tetrapods using an earlier stage of quadrupedal locomotion that was powered primarily by the hind limbs (i.e., "rear-wheel drive"), and reveal mechanisms for appendages to generate propulsion in three locomotor strategies that are presumed to have occurred across the water-to-land transition in vertebrate evolution.
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Palaeobatrachus minutus & P. codreavladi sp. nov.
ZbynÄk RoÄek, Jean-Claude Rage & MÃrton Venczel (2021)
Fossil frogs of the genus Palaeobatrachus (Amphibia: Anura).
Abhandlungen der Senckenberg Gesellschaft fÃr Naturforschung 575: 151 pages
ISBN 978-3-510-61420-2
https://www.schweizerbart.de/publications/detail/isbn/9783510614202/Abh_d_Senckenb_Gesf_Naturforschung
Palaeobatrachidae are an extinct family of frogs whose earliest members are recorded from the Middle Eocene (Geiseltal, Messel, Germany), almost 50 million years ago, although there are indications that they appeared as early as before the Cretaceous mass extinction event and survived almost to our times. Their last survivors are recorded from the Middle Pleistocene, less than 0.5 million years ago, such that they were contemporaries of Neanderthal man. Their last fossil evidence is from the regions that were adjacent to the Pleistocene continental glacier. Like todayâs pipid frogs (e.g. Xenopus), they were obligate water dwellers, not able to make long excursions onto dry land. Without exaggerating, they literally died out frozen in their ponds.
Permanent life in water has a uniforming effect. This is why they all looked similar to one another, which is a source of difficulty for taxonomists. On the other hand, one cannot overlook features they have in common with pipids, restricted to the southern hemisphere. Palaeobatrachus and Xenopus are undoubtedly related, but when and why ancestors of Palaeobatrachus immigrated to the western part of northern Eurasia but not to its eastern part and not to North America remains a puzzling question. Thus, being acquainted with Palaeobatrachus means to be invited on an excursion not only into comparative anatomy, but also into paleogeography and many other fields of palaeontology.
Last but not least, Palaeobatrachus was the first fossil frog scientifically described, as early as in 1831. Since that time, many excavation sites from which original material came have ceased to exist; thus there is no possibility that further material will be recovered. What is now deposited in scientific collections is the unique and limited source of data for future comparative studies. This is one of the main reasons why this rich illustrated review was published.
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Free pdf:
Alessia Huby, Rohan Mansuit, Marc Herbin & Anthony Herrel (2021)
Revision of the muscular anatomy of the paired fins of the living coelacanth Latimeria chalumnae (Sarcopterygii: Actinistia).
Biological Journal of the Linnean Society, blab047
doi: https://doi.org/10.1093/biolinnean/blab047
https://academic.oup.com/biolinnean/advance-article/doi/10.1093/biolinnean/blab047/6261035
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As a sarcopterygian fish, the extant coelacanth Latimeria has muscular paired fins, different in their skeletal and muscular anatomy from the paired fins of actinopterygians. Although the muscular anatomy of the pectoral and pelvic fins of Latimeria has been described by several studies, a detailed functional description of the muscles and their architecture has never been performed. Our detailed functional description of the muscles of the paired fins shows a more complex organization than previously described. The pectoral and pelvic fins have a different organization of their muscular anatomy, and the pelvic fin shows a more plesiomorphic configuration of the muscles since most of them are poly-articular and run from the pelvic girdle to the fin rays, an organization typical of actinopterygians. We found that the pectoral fins are stronger than the pelvic fins which is likely to be associated with the greater contribution of the pectoral fins to locomotion and manoeuvring. Finally, the study of the joint mobility of the paired fins showed that the pectoral fins show greater mobility than the pelvic fins. The reduced mobility of the pelvic fin is possibly a consequence of the morphology of the mesomeres and the large pre-axial radials.
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Free pdf:
Only free from April 21- May 5, 2021!
Laura C. Soul & David F. Wright (2021)
Phylogenetic Comparative Methods: A User's Guide for Paleontologists
Elements of Paleontology
https://www.cambridge.org/core/elements/phylogenetic-comparative-methods-a-users-guide-for-paleontologists/973B90CCB6F4B9E07CE23793F1E4D1AD
Recent advances in statistical approaches called Phylogenetic Comparative Methods (PCMs) have provided paleontologists with a powerful set of analytical tools for investigating evolutionary tempo and mode in fossil lineages. However, attempts to integrate PCMs with fossil data often present workers with practical challenges or unfamiliar literature. This Element presents guides to the theory behind, and the application of, PCMs with fossil taxa. Based on an empirical dataset of Paleozoic crinoids, it presents example analyses to illustrate common applications of PCMs to fossil data, including investigating patterns of correlated trait evolution and macroevolutionary models of morphological change. It then emphasizes the importance of accounting for sources of uncertainty and discusses how to evaluate model fit and adequacy. Finally, this Element discusses several promising methods for modelling heterogeneous evolutionary dynamics with fossil phylogenies. Integrating phylogeny-based approaches with the fossil record provides a rigorous, quantitative perspective to understanding key patterns in the history of life.
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