Crocodyliform skull evolution + embryonic caiman skull + mekosuchine eggshell + dicynodont phylogeny
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Ben Creisler
Nov 12, 2025, 1:34:22 AMNov 12
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Ben Creisler
Some recent papers:
Free pdf:
Ananth Srinivas, Jen A. Bright, John A. Cunningham, Sandra Aparecida Simionato Tavares, Fresia Ricardi-Branco, Ismar de Souza Carvalho, Fabiano Vidoi Iori and Emily J. Rayfield (2025)
Constraints and adaptations in crocodyliform skull evolution
Proceedings of the Royal Society B: Biological Sciences 292(2058): 20251773
doi: https://doi.org/10.1098/rspb.2025.1773
https://royalsocietypublishing.org/doi/10.1098/rspb.2025.1773
Free pdf:
https://royalsocietypublishing.org/doi/epdf/10.1098/rspb.2025.1773
Crocodyliforms display a diverse range of skull morphologies through their evolutionary history. Extant crocodilians possess platyrostral (broad and flat) snouts, thought to be sub-optimal for resisting feeding loads due to the conflicting demands of feeding and hydrodynamic constraints. In contrast, numerous Mesozoic crocodyliforms possessed oreinirostral (dome-shaped) skulls, were terrestrial and hence free from hydrodynamic constraint. This study aims to examine the role of function in determining skull shape in crocodyliforms and assesses the difference in stress resistance between oreinirostral and platyrostral taxa. We hypothesize that in the absence of hydrodynamic constraints, oreinirostral taxa have skulls that are better suited for resisting feeding-induced loads. Using finite element analysis, we evaluated biomechanical performance in oreinirostral notosuchian taxa Baurusuchus salgadoensis, Montealtosuchus arrudacamposi and Caipirasuchus paulistanus, compared to the extant platyrostral Alligator mississippiensis, Crocodylus niloticus and Paleosuchus palpebrosus. Results show that oreinirostral morphologies are comparatively better suited for resisting forces generated during feeding, with increased muscular efficiency, supporting the hypothesis that hydrodynamic constraints influence crocodyliform skull evolution.
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Free pdf:
María Victoria Fernandez Blanco and Ingmar Werneburg (2025)
Structure and evolution of the embryonic cartilaginous skull of crocodilians
Royal Society Open Science 12(11): 251281
doi: https://doi.org/10.1098/rsos.251281
https://royalsocietypublishing.org/doi/10.1098/rsos.251281
Free pdf:
https://royalsocietypublishing.org/doi/epdf/10.1098/rsos.251281
Structure and evolution of the embryonic cartilaginous skull of crocodilians
Royal Society Open Science 12(11): 251281
doi: https://doi.org/10.1098/rsos.251281
https://royalsocietypublishing.org/doi/10.1098/rsos.251281
Free pdf:
https://royalsocietypublishing.org/doi/epdf/10.1098/rsos.251281
The evolution of skull diversity in Crocodylia is rather well documented, but the developmental foundation of their cranial architecture remains poorly understood. Here, we present the first three-dimensional reconstruction of the embryonic cartilaginous skull of Caiman crocodilus based on histological sections. We provide a comprehensive anatomical description and morphometric analysis of the chondrocranium of this species, integrating linear measurements and comparative anatomical data to assess interspecific variation and evaluate whether closely related taxa exhibit greater similarity in chondrocranial morphology. We identified both qualitative and quantitative differences between major crocodilian clades, which may reflect diverse ecological demands. Within Crocodylidae, orbitotemporal proportions strongly influence chondrocranial morphology, likely reflecting adaptations related to bite force and visual acuity, linked to prey type and diverse aquatic habits. Within Alligatoridae, by contrast, the emphasis on nasal capsule proportions suggests a reliance on olfactory and respiratory functions, consistent with their occupation of densely vegetated environments and more restricted geographic ranges. Additionally, we identified a set of embryonic diagnostic features located in the splanchnocranium of Caiman and in the neurocranium of Alligatoridae. These findings shed new light on the developmental basis of cranial diversity in Crocodylia and emphasize the evolutionary significance of chondrocranial traits in shaping macroevolutionary patterns.
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Wakkaoolithus godthelpi oogen. et oosp. nov.
Xavier Panadès I Blas, Àngel Galobart, Michael Archer, Michael Stein, Suzanne Hand & Albert Sellés (2025)
Australia’s oldest crocodylian eggshell: insights into the reproductive paleoecology of mekosuchines
Journal of Vertebrate Paleontology e2560010
doi: https://doi.org/10.1080/02724634.2025.2560010
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2560010
Alongside large madtsoiid snakes, the largest known lizards, thylacoleonid marsupials and a range of other terrestrial carnivores, the now extinct mekosuchine crocodylians were significant predators during most of the Cenozoic in Australia. Although the skeletal fossil record for mekosuchines extends from the lower Eocene through the Quaternary, fossil evidence relating to their reproductive biology (e.g., eggshells, eggs, clutches, or nests) has been reported but not studied. Here, we describe Australia’s oldest crocodylian eggshell from the purple layer of the lower Eocene Tingamarra Local Fauna of the Oakdale Sandstone of Murgon, south-eastern Queensland, Australia. The eggshells belong to a new crocodylian eggshell type which differs structurally from all other crocodylomorph eggshells. Given the abundance in the Tingamarra deposits of specimens representing two mekosuchine crocodylians, both referable to species of Kambara and with no other crocodylians being present in this deposit, it is parsimonious to presume that these eggshells were produced by one or both of these mekosuchine species. A preliminary taphonomic analysis of the oological remains sheds light on aspects of the reproductive behavior of these mekosuchines.
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Australia’s oldest crocodylian eggshell: insights into the reproductive paleoecology of mekosuchines
Journal of Vertebrate Paleontology e2560010
doi: https://doi.org/10.1080/02724634.2025.2560010
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2560010
Alongside large madtsoiid snakes, the largest known lizards, thylacoleonid marsupials and a range of other terrestrial carnivores, the now extinct mekosuchine crocodylians were significant predators during most of the Cenozoic in Australia. Although the skeletal fossil record for mekosuchines extends from the lower Eocene through the Quaternary, fossil evidence relating to their reproductive biology (e.g., eggshells, eggs, clutches, or nests) has been reported but not studied. Here, we describe Australia’s oldest crocodylian eggshell from the purple layer of the lower Eocene Tingamarra Local Fauna of the Oakdale Sandstone of Murgon, south-eastern Queensland, Australia. The eggshells belong to a new crocodylian eggshell type which differs structurally from all other crocodylomorph eggshells. Given the abundance in the Tingamarra deposits of specimens representing two mekosuchine crocodylians, both referable to species of Kambara and with no other crocodylians being present in this deposit, it is parsimonious to presume that these eggshells were produced by one or both of these mekosuchine species. A preliminary taphonomic analysis of the oological remains sheds light on aspects of the reproductive behavior of these mekosuchines.
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News:
Australian 'drop crocs' unlock insights into ancient ecosystems
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Brenen M Wynd, Basanta Khakurel, Christian F Kammerer, Peter J Wagner & April M Wright (2025)
Incorporating continuous characters in joint estimation of dicynodont phylogeny
Systematic Biology, syaf078
doi: https://doi.org/10.1093/sysbio/syaf078
https://academic.oup.com/sysbio/advance-article-abstract/doi/10.1093/sysbio/syaf078/8320520
Continuous characters have received comparatively little attention in Bayesian phylogenetic estimation. This is predominantly because they cannot be modeled by a standard phylogenetic Q-matrix approach due to their non-discrete nature. In this paper, we explore the use of continuous traits under two Brownian motion models to estimate a phylogenetic tree for Dicynodontia, a well-studied group of early synapsids (stem mammals) in which both discrete and continuous characters have been extensively used in parsimony-based tree reconstruction. We examine the differences in phylogenetic signal between a continuous trait partition, a discrete trait partition, and a joint analysis with both types of characters. We find that continuous and discrete traits contribute substantially different signal to the analysis, even when other parts of the model (clock and tree) are held constant. Tree topologies resulting from the new analyses differ strongly from the established phylogeny for dicynodonts, highlighting continued difficulty in incorporating truly continuous data in a Bayesian phylogenetic framework.
Systematic Biology, syaf078
doi: https://doi.org/10.1093/sysbio/syaf078
https://academic.oup.com/sysbio/advance-article-abstract/doi/10.1093/sysbio/syaf078/8320520
Continuous characters have received comparatively little attention in Bayesian phylogenetic estimation. This is predominantly because they cannot be modeled by a standard phylogenetic Q-matrix approach due to their non-discrete nature. In this paper, we explore the use of continuous traits under two Brownian motion models to estimate a phylogenetic tree for Dicynodontia, a well-studied group of early synapsids (stem mammals) in which both discrete and continuous characters have been extensively used in parsimony-based tree reconstruction. We examine the differences in phylogenetic signal between a continuous trait partition, a discrete trait partition, and a joint analysis with both types of characters. We find that continuous and discrete traits contribute substantially different signal to the analysis, even when other parts of the model (clock and tree) are held constant. Tree topologies resulting from the new analyses differ strongly from the established phylogeny for dicynodonts, highlighting continued difficulty in incorporating truly continuous data in a Bayesian phylogenetic framework.
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