Thalattosuchia and Dyrosauridae pectoral girdle + ziphodont crocodylians during Pliocene of New Guinea + crown reptile traits evolutionary assembly + "Yinshanosaurus" Chinese pareiasaur of
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Ben Creisler
Nov 30, 2024, 3:59:47 PMNov 30
to DinosaurMa...@googlegroups.com
Ben Creisler
Crocodylomorphs have colonized various environments from fully terrestrial to fully aquatic, making it an important clade among archosaurs. A remarkable example of the rich past diversity of Crocodylomorpha Hay, 1930 is the marine colonization undergone by several crocodylomorph lineages, particularly Thalattosuchia Fraas, 1901 during the Early Jurassic–Early Cretaceous, and Dyrosauridae de Stefano, 1903 during the Late Cretaceous–Early Eocene. Thalattosuchia represents the most impressive and singular marine radiation among Crocodylomorpha, occupying various ecological niches, before enigmatically disappearing in the Cretaceous. Dyrosauridae, on the other hand, is known for surviving the end-Cretaceous mass extinction in abundance but subsequently vanished. The evolutionary path undertaken by crocodylomorphs into the aquatic environments and the reasons for their disappearance outside marine extinction events during the Mesozoic remains a mystery. Despite a well-preserved fossil record, attention has primarily centered on craniodental adaptations, overlooking the swimming-related adaptations recorded in the postcranial skeleton. This research primarily involves a comprehensive examination of the pectoral girdle of the most representative members of Thalattosuchia and Dyrosauridae, highlighting their evolutionary trajectories over time. Additionally, this work aims to test the phylogenetic signal residing in the postcranial anatomy of Crocodylomorpha. As such, the most recent and complete Crocodylomorpha phylogenetic dataset has been repurposed: 42 new postcranial characters have been added and several others have been revised to address our phylogenetic question. We stress that postcranial anatomy constitutes an important tool supply to better understand the relations of extinct crocodyliforms, but also offers insights on their development, ecology, and biomechanics.
The original publication on the Pliocene Otibanda Formation in Papua New Guinea briefly reported on crocodyliform fossils, including isolated teeth that were tentatively assigned to the notosuchian subclade Sebecosuchia. In this study, we reassess the crocodyliform material from the Otibanda Formation and provide the first detailed descriptions of the same, including the purported sebecosuchian teeth. Direct examination of these teeth confirms their ziphodont condition based on the labiolingual compression of the crowns and the presence of serrated mesial and distal carinae. In addition to the ziphodont teeth, there are also non-serrate conical teeth that are tentatively referred to an undetermined species of Crocodylus as well as fragmentary postcranial elements that we refer to as Crocodylia incertae sedis. Considering the geological age and geographical origin of the isolated ziphodont tooth crowns from Papua New Guinea, they are unlikely to belong to a sebecosuchian crocodyliform. Instead, it is more plausible that they are referable to Mekosuchinae, a highly diverse crocodylian clade inclusive of ziphodont forms that was prevalent on mainland Australia for most of the Cenozoic.
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Xavier A. Jenkins, Roger B. J. Benson, David P. Ford, Claire Browning, Vincent Fernandez, Kathleen Dollman, Timothy Gomes, Elizabeth Griffiths, Jonah N. Choiniere & Brandon R. Peecook (2024)
Stepwise Assembly Of Crown Reptile Anatomy Clarified By Late Paleozoic Outgroups Of Neodiapsida
bioRxiv 2024.11.25.625221 (preprint)
doi: https://doi.org/10.1101/2024.11.25.625221
https://www.biorxiv.org/content/10.1101/2024.11.25.625221v1
Living reptiles include more than 20,000 species with disparate ecologies. Direct anatomical evidence from Neodiapsida, which includes the reptile crown-group Sauria and its closest extinct relatives, shows that this diversity originates from a single common reptilian ancestor that lived some 255 million years ago in the Paleozoic. However, the evolutionary assembly of crown reptile traits is poorly understood due to the lack of anatomically close outgroups to Neodiapsida1–7. We present a substantially revised phylogenetic hypothesis, informed by new anatomical data derived from high-resolution synchrotron tomography of Paleozoic reptiles8–12. We find strong evidence placing the clade Millerettidae as a close sister to Neodiapsida, which uniquely share a suite of derived features among Paleozoic stem reptiles. This grouping, for which we name the new clade Parapleurota, replaces previous phylogenetic paradigms by rendering the group Parareptilia as a polyphyletic assemblage of stem reptiles, of which millerettids are the most crownward. Our analysis presents hypotheses that resolve long-standing issues in Paleozoic reptile evolution, including the placement of captorhinids on the amniote stem lineage and firm support for varanopids as synapsids, which taken together provide a greatly improved fit to the observed stratigraphic record. Optimizations of character evolution on our phylogenetic hypothesis reveals gradual assembly of crown reptile anatomy, including a Permian origin of tympanic hearing, the presence of a lower temporal fenestra in the amniote common ancestor, with subsequent modifications on the reptile stem lineage, leading to the loss of the lower temporal bar. This evolutionary framework provides a platform for investigating the subsequent radiations of the reptile crown group in the Early Triassic, including the lines leading to dinosaurs (including birds), crocodilians, lepidosaurs, and extinct marine reptiles.
Jian Yi & Jun Liu (2024)
The tetrapod fauna of the upper Permian Naobaogou Formation of China: a new mid-sized pareiasaur Yinshanosaurus angustus gen. et sp. nov. and its implication for the phylogenetic relationship of pareiasaurs
bioRxiv 2024.11.23.624968 (preprint)
doi: https://doi.org/10.1101/2024.11.23.624968
https://www.biorxiv.org/content/10.1101/2024.11.23.624968v1
Pareiasauria is a specialized clade of herbivorous tetrapods that existed throughout Pangaea during the mid to late Permian period. The phylogenetic relationships of Chinese pareiasaur species remain controversy for several decades, primarily due to the poor preservation of known specimens. Until the report of Shihtienfenia completus in 2019, no complete skull had been documented for Chinese pareiasaurs. The present study describes a mid-sized pareiasaur, Yinshanosaurus angustus gen. et sp. nov., based on a nearly complete skull and an articulated partial postcranial skeleton collected from the Naobaogou Formation in 2018. It presents several significant new morphological features such as high and narrow skull, with the length of the skull table exceeding the width between the two quadratojugals; snout dimension as high as wide; long frontal with a length-to-width ratio of ∼3.0; U-shaped paraoccipital process in occipital view; and maxillary teeth oriented vertically, with only 7-9 cusps. Although the phylogenetic framework of pareiasaurs still requires further refinement, the current analysis yields distinct phylogenetic positions for Chinese pareiasaurs and establishes a new monophyletic clade that includes S. completus and Y. angustus.
Not yet mentioned reptile papers:
Isaure Scavezzoni, Michela M. Johnson, Stéphane Jouve & Valentin Fischer (2024)
Functional and phylogenetic signals in the pectoral girdle of Thalattosuchia and Dyrosauridae (Crocodylomorpha)
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.25596
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25596
Functional and phylogenetic signals in the pectoral girdle of Thalattosuchia and Dyrosauridae (Crocodylomorpha)
The Anatomical Record (advance online publication)
doi: https://doi.org/10.1002/ar.25596
https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25596
Crocodylomorphs have colonized various environments from fully terrestrial to fully aquatic, making it an important clade among archosaurs. A remarkable example of the rich past diversity of Crocodylomorpha Hay, 1930 is the marine colonization undergone by several crocodylomorph lineages, particularly Thalattosuchia Fraas, 1901 during the Early Jurassic–Early Cretaceous, and Dyrosauridae de Stefano, 1903 during the Late Cretaceous–Early Eocene. Thalattosuchia represents the most impressive and singular marine radiation among Crocodylomorpha, occupying various ecological niches, before enigmatically disappearing in the Cretaceous. Dyrosauridae, on the other hand, is known for surviving the end-Cretaceous mass extinction in abundance but subsequently vanished. The evolutionary path undertaken by crocodylomorphs into the aquatic environments and the reasons for their disappearance outside marine extinction events during the Mesozoic remains a mystery. Despite a well-preserved fossil record, attention has primarily centered on craniodental adaptations, overlooking the swimming-related adaptations recorded in the postcranial skeleton. This research primarily involves a comprehensive examination of the pectoral girdle of the most representative members of Thalattosuchia and Dyrosauridae, highlighting their evolutionary trajectories over time. Additionally, this work aims to test the phylogenetic signal residing in the postcranial anatomy of Crocodylomorpha. As such, the most recent and complete Crocodylomorpha phylogenetic dataset has been repurposed: 42 new postcranial characters have been added and several others have been revised to address our phylogenetic question. We stress that postcranial anatomy constitutes an important tool supply to better understand the relations of extinct crocodyliforms, but also offers insights on their development, ecology, and biomechanics.
====
Jorgo Ristevski, Ralph E. Molnar & Adam M. Yates (2024)
Reassessment of isolated reptilian teeth confirms the presence of ziphodont crocodylians during the Pliocene of New Guinea
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2024.2429585
https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2429585
Reassessment of isolated reptilian teeth confirms the presence of ziphodont crocodylians during the Pliocene of New Guinea
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2024.2429585
https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2429585
The original publication on the Pliocene Otibanda Formation in Papua New Guinea briefly reported on crocodyliform fossils, including isolated teeth that were tentatively assigned to the notosuchian subclade Sebecosuchia. In this study, we reassess the crocodyliform material from the Otibanda Formation and provide the first detailed descriptions of the same, including the purported sebecosuchian teeth. Direct examination of these teeth confirms their ziphodont condition based on the labiolingual compression of the crowns and the presence of serrated mesial and distal carinae. In addition to the ziphodont teeth, there are also non-serrate conical teeth that are tentatively referred to an undetermined species of Crocodylus as well as fragmentary postcranial elements that we refer to as Crocodylia incertae sedis. Considering the geological age and geographical origin of the isolated ziphodont tooth crowns from Papua New Guinea, they are unlikely to belong to a sebecosuchian crocodyliform. Instead, it is more plausible that they are referable to Mekosuchinae, a highly diverse crocodylian clade inclusive of ziphodont forms that was prevalent on mainland Australia for most of the Cenozoic.
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Preprints (not yet peer-reviewed)
Free pdf:
Xavier A. Jenkins, Roger B. J. Benson, David P. Ford, Claire Browning, Vincent Fernandez, Kathleen Dollman, Timothy Gomes, Elizabeth Griffiths, Jonah N. Choiniere & Brandon R. Peecook (2024)
Stepwise Assembly Of Crown Reptile Anatomy Clarified By Late Paleozoic Outgroups Of Neodiapsida
bioRxiv 2024.11.25.625221 (preprint)
doi: https://doi.org/10.1101/2024.11.25.625221
https://www.biorxiv.org/content/10.1101/2024.11.25.625221v1
Living reptiles include more than 20,000 species with disparate ecologies. Direct anatomical evidence from Neodiapsida, which includes the reptile crown-group Sauria and its closest extinct relatives, shows that this diversity originates from a single common reptilian ancestor that lived some 255 million years ago in the Paleozoic. However, the evolutionary assembly of crown reptile traits is poorly understood due to the lack of anatomically close outgroups to Neodiapsida1–7. We present a substantially revised phylogenetic hypothesis, informed by new anatomical data derived from high-resolution synchrotron tomography of Paleozoic reptiles8–12. We find strong evidence placing the clade Millerettidae as a close sister to Neodiapsida, which uniquely share a suite of derived features among Paleozoic stem reptiles. This grouping, for which we name the new clade Parapleurota, replaces previous phylogenetic paradigms by rendering the group Parareptilia as a polyphyletic assemblage of stem reptiles, of which millerettids are the most crownward. Our analysis presents hypotheses that resolve long-standing issues in Paleozoic reptile evolution, including the placement of captorhinids on the amniote stem lineage and firm support for varanopids as synapsids, which taken together provide a greatly improved fit to the observed stratigraphic record. Optimizations of character evolution on our phylogenetic hypothesis reveals gradual assembly of crown reptile anatomy, including a Permian origin of tympanic hearing, the presence of a lower temporal fenestra in the amniote common ancestor, with subsequent modifications on the reptile stem lineage, leading to the loss of the lower temporal bar. This evolutionary framework provides a platform for investigating the subsequent radiations of the reptile crown group in the Early Triassic, including the lines leading to dinosaurs (including birds), crocodilians, lepidosaurs, and extinct marine reptiles.
====
Free pdf:
"Yinshanosaurus angustus" gen. et sp. nov. (not official)
"Yinshanosaurus angustus" gen. et sp. nov. (not official)
Jian Yi & Jun Liu (2024)
The tetrapod fauna of the upper Permian Naobaogou Formation of China: a new mid-sized pareiasaur Yinshanosaurus angustus gen. et sp. nov. and its implication for the phylogenetic relationship of pareiasaurs
bioRxiv 2024.11.23.624968 (preprint)
doi: https://doi.org/10.1101/2024.11.23.624968
https://www.biorxiv.org/content/10.1101/2024.11.23.624968v1
Pareiasauria is a specialized clade of herbivorous tetrapods that existed throughout Pangaea during the mid to late Permian period. The phylogenetic relationships of Chinese pareiasaur species remain controversy for several decades, primarily due to the poor preservation of known specimens. Until the report of Shihtienfenia completus in 2019, no complete skull had been documented for Chinese pareiasaurs. The present study describes a mid-sized pareiasaur, Yinshanosaurus angustus gen. et sp. nov., based on a nearly complete skull and an articulated partial postcranial skeleton collected from the Naobaogou Formation in 2018. It presents several significant new morphological features such as high and narrow skull, with the length of the skull table exceeding the width between the two quadratojugals; snout dimension as high as wide; long frontal with a length-to-width ratio of ∼3.0; U-shaped paraoccipital process in occipital view; and maxillary teeth oriented vertically, with only 7-9 cusps. Although the phylogenetic framework of pareiasaurs still requires further refinement, the current analysis yields distinct phylogenetic positions for Chinese pareiasaurs and establishes a new monophyletic clade that includes S. completus and Y. angustus.
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