A Thin-Shelled Reptile from The Late Triassic of North America and the Origin of the Turtle Shell

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Andrew B. Heckert Ph.D., Professor (Creator)
Appalachian State University (ASU )
Web Site: https://library.appstate.edu/

Abstract: A new, thin-shelled fossil from the Upper Triassic (Revueltian: Norian) Chinle Group of New Mexico, Chinlechelys tenertesta, is one of the most primitive known unambiguous members of the turtle stem lineage. The thin-shelled nature of the new turtle combined with its likely terrestrial habitat preference hint at taphonomic filters that basal turtles had to overcome before entering the fossil record. Chinlechelys tenertesta possesses neck spines formed by multiple osteoderms, indicating that the earliest known turtles were covered with rows of dermal armour. More importantly, the primitive, vertically oriented dorsal ribs of the new turtle are only poorly associated with the overlying costal bones, indicating that these two structures are independent ossifications in basal turtles. These novel observations lend support to the hypothesis that the turtle shell was originally a complex composite in which dermal armour fused with the endoskeletal ribs and vertebrae of an ancestral lineage instead of forming de novo. The critical shell elements (i.e. costals and neurals) are thus not simple outgrowths of the bone of the endoskeletal elements as has been hypothesized from some embryological observations.

Additional Information

Andrew B. Heckert, Walter G. Joyce, Spencer G. Lucas, Torsten M. Scheyer, and Adrian P. Hunt (2009) "A Thin-Shelled Reptile from The Late Triassic of North America and the Origin of the Turtle Shell" Proceedings of the Royal Society B: Biological Sciences Volume 276 Issue 1656 pp. 507-513 Version of Record Available From (www.royalsocietypublishing.org)
Language: English
Date: 2009
Triassic, New Mexico, Testudinata, Chinlechelys tenertesta, origin of turtle shell

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