Ben Creisler
New papers:
Free pdf:
Manabu Sakamoto (2020)
Assessing bite force estimates in extinct mammals and archosaurs using phylogenetic predictions.
bioRxiv 2020.11.17.386771 (preprint)
doi: https://doi.org/10.1101/2020.11.17.386771
https://www.biorxiv.org/content/10.1101/2020.11.17.386771v1
Bite force is an ecologically important biomechanical performance measure is informative in inferring the ecology of extinct taxa. However, biomechanical modelling to estimate bite force is associated with some level of uncertainty. Here, I assess the accuracy of bite force estimates in extinct taxa using a Bayesian phylogenetic prediction model. I first fitted a phylogenetic regression model on a training set comprising extant data. The model predicts bite force from body mass and skull width while accounting for differences owning to biting position. The posterior predictive model has a 93% prediction accuracy as evaluated through leave-one-out cross-validation. I then predicted bite force in 37 species of extinct mammals and archosaurs from the posterior distribution of predictive models. Biomechanically estimated bite forces fall within the posterior predictive distributions for all except four species of extinct taxa, and are thus as accurate as that predicted from body size and skull width, given the variation inherent in extant taxa and the amount of time available for variance to accrue. Biomechanical modelling remains a valuable means to estimate bite force in extinct taxa and should be reliably informative of functional performances and serve to provide insights into past ecologies.
===
Ray Brasil Bueno de Souza, Vanessa Maria Gomes Bonfim, Vitor Passos Rios & Wilfried Klein (2020)
Allometric relations of respiratory variables in Amniota: Effects of phylogeny, form, and function.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology (advance online publication)
doi: https://doi.org/10.1016/j.cbpa.2020.110845
https://www.sciencedirect.com/science/article/pii/S1095643320301987
Highlights
Allometric relations of respiratory variables are being compiled and analyzed from phylogenetic and functional viewpoints for reptiles for the first time, and compared to birds and mammals.
Function related variables such as tidal volume, breathing frequency (except in mammals), and air convection requirement were independent of phylogeny.
Contrary to the literature, lung volume of reptiles, excluding lizards (MB0.78), scaled isometrically with MB, just as seen in birds and mammals,
Air convection requirement scaled isometrically in mammals and birds, but was more variable among reptiles, both from a taxonomic perspective as well as regarding different lung structures.
Despite more than a century of studies on breathing in reptiles, groups like crocodilians and snakes are still very poorly represented in the literature, both regarding the number of species studied, as well as the possible body sizes available, indicating still a need for studies in comparative respiratory physiology.
Abstract
Biological variables are frequently described by analyzing scaling relationships of the variable against body mass (MB). Respiratory variables are no exception and allometric relations for oxygen consumption, pulmonary ventilation, tidal volume, breathing frequency, and lung volume have been described in the literature. While the allometric relations of respiratory variables given for mammals and birds are very consistent among different studies, scaling relationships for non-avian reptiles have only been scarcely described and show considerable variation between studies. Since no comprehensive study of allometric relations of respiratory variables has been carried out comparing the different groups of non-avian reptiles, we analyzed morphological and physiological variables of the respiratory system of crocodilians, chelonians, lizards, snakes, birds, and mammals, regarding the allometric relations of each variable from a phylogenetic perspective as well as related to lung morphology. Our results indicated that few respiratory variables possess significant phylogenetic signals and that tidal volume, breathing frequency (except mammals), and air convection requirement were independent of phylogeny. Contrary to the literature, lung volume of amniotes scaled isometrically to MB, with the exception of lizards (MB0.78). Air convection requirement scaled isometrically in mammals and birds, but was more variable among non-avian reptiles, from a taxonomic perspective and in regard to different lung structures. In conclusion, respiratory variables among non-avian reptiles scaled more variably than previously expected, both according to phylogeny and to lung type, warranting future studies to explore structure-function relations of the reptilian respiratory system, especially regarding snakes and crocodilians, since these groups had very few data available for analysis.
=====
New record of a Mesozoic gondwanatherian mammaliaform from Southern Patagonia.
The Science of Nature 107(49) (advance online publication)
doi: https://doi.org/10.1007/s00114-020-01705-x
https://link.springer.com/article/10.1007/s00114-020-01705-x
Gondwanatheria is an enigmatic mammaliaform clade distributed in the Cretaceous and Paleogene of South America, Africa, Madagascar, India and Antarctica. The Mesozoic record in South America is restricted to the Latest Cretaceous of RÃo Negro and Chubut provinces, Argentina and Magallanes Region of southern Chile. The aim of the present contribution is to describe a new specimen of gondwanatherian mammaliaforms from beds belonging to the Maastrichtian Chorrillo Formation, cropping out 30 km SW of El Calafate, Santa Cruz Province, Argentina. It is represented by a single molariform referable to the species Magallanodon baikashkenke with which it shares a unique combination of characters. Analysis of the unique combination of characters exhibited by Magallanodon shed doubts on the monophyly of Ferugliotheriidae and suggest that South American taxa may be closely related to each other. The wide geographical distribution and occurrence of gondwanatherians on geological units of diverse origins suggest that they were capable of facing disparate environmental conditions.
====
Lachlan J. Hart, Phil R. Bell, Elizabeth T. Smith, D. Rex Mitchell, Tom Brougham and Steven W. Salisbury (2020)
A probable skeleton of Isisfordia (Crocodyliformes) and additional crocodyliform remains from the Griman Creek Formation (Cenomanian, New South Wales, Australia).
Journal of Paleontology (advance online publication)
DOI: https://doi.org/10.1017/jpa.2020.98
https://www.cambridge.org/core/journals/journal-of-paleontology/article/probable-skeleton-of-isisfordia-crocodyliformes-and-additional-crocodyliform-remains-from-the-griman-creek-formation-cenomanian-new-south-wales-australia/F19841B25CE2E26ECA9BDF4F44095A62
The sparse record of Cretaceous crocodyliforms in Australia comprises only three species, all within the genus Isisfordia. Isisfordia duncani Salisbury et al., 2006 is from the AlbianâTuronian Winton Formation of Queensland, and both Isisfordia molnari Hart et al., 2019 and Isisfordia selaslophensis Etheridge, 1917 have been described from opalized material from the Cenomanian Griman Creek Formation of New South Wales. Here, we describe new cranial and postcranial material, including the most complete crocodyliform skeleton from the Cretaceous of New South Wales, which is assigned to Isisfordia cf. I. selaslophensis. We also reappraise previously described crocodyliform material from the same locality. We find that much of this material displays features that are consistent with Isisfordia.
===