Sonselasuchus, new shuvosaurid (Poposauroidea) from Upper Triassic Chinle Formation, Petrified Forest National Park, Arizona (free to read)

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

A new paper:

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Free access (I can't download it for now):

Sonselasuchus cedrus, gen. et sp. nov.

Elliott Armour Smith &Christian A. Sidor (2026)
Osteology and relationships of a new shuvosaurid (Pseudosuchia, Poposauroidea) from the Upper Triassic Chinle Formation of Petrified Forest National Park, Arizona, U.S.A.
Journal of Vertebrate Paleontology e2604859
doi: https://doi.org/10.1080/02724634.2025.2604859
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2604859

Free to read:
https://www.tandfonline.com/doi/epdf/10.1080/02724634.2025.2604859


Shuvosauridae is a clade of pseudosuchian archosaurs currently represented by three named species characterized by a body plan strikingly convergent with that of ornithomimid theropod dinosaurs. This paper documents a new genus and species of shuvosaurid from the Upper Triassic Chinle Formation of Petrified Forest National Park, Arizona. Sonselasuchus cedrus, gen. et sp. nov., is largely diagnosed by features of the maxilla, including a reduced body and anterior process, an enlarged subnarial foramen, and an expanded facet on the posterior process, although other unique cranial features are also noted herein. By contrast, its postcranial anatomy is largely similar to what has been described for other shuvosaurids, although subtle differences are noted. A phylogenetic analysis finds S. cedrus in an unresolved clade with Effigia okeeffeae and Shuvosaurus inexpectatus, likely as a result of non-overlapping missing data, particularly for the skull of Shuvosaurus. A review of the shuvosaurid fossil record indicates that shuvosaurids were persistent components of Late Triassic terrestrial vertebrate faunas in North America. S. cedrus is represented by a minimum number of 36 individuals, mostly skeletally immature, that occur within a multitaxic bonebed of almost exclusively disarticulated elements. An analysis of the relative size change of limb dimensions indicates the forelimb was growing on a negative allometric trajectory relative to the hindlimb, which is consistent with a transition in locomotory mode from quadrupedal to bipedal in S. cedrus during ontogeny.

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News:

https://www.eurekalert.org/news-releases/1118722

https://www.discovermagazine.com/a-25-inch-crocodile-relative-walked-on-two-legs-in-late-triassic-forests-225-million-years-ago-48787

https://www.newscientist.com/article/2518365-ancient-weirdo-reptile-graduated-from-4-legs-to-2-in-adolescence/

https://novataxa.blogspot.com/2026/03/sonselasuchus.html

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