Principal reference section for the Santa Rosa formation of Middle and Late Triassic age, Guadalupe County, New Mexico

10.3133/b1804 ◽  
1988 ◽  

2014 ◽  
Author(s):  
Robert J Gay ◽  
Isabella St. Aude

Originally identified as an ornithisichian dinosaur, Crosbysaurus has been found in New Mexico, Arizona, and the type locality in Texas. The genus has been reassessed by other workers in light of revelations about the postcrania of another putative Triassic ornithischian, Revueltosaurus. The understanding of Triassic dental faunas has become more complicated by the extreme convergence between pseudosuchian archosaurus and ornithichian dinosaur dental morphologies. We report here on a new specimen of Crosbysaurus from the Petrified Forest Member of the Chinle Formation at Comb Ridge in southeastern Utah. This new specimen is assigned to Crosbysaurus on the basis of the unique compound posterior denticles, mediolateral width, and curvature. While this specimen, MNA V10666, does not help resolve the affinities of Crosbysaurus it does represent an approximately 250 kilometer extension of the geographic range of this taxon. This is the first record of this taxon in Utah and as such it represents the northernmost known record of Crosbysaurus. This indicates that Crosbysaurus was not limited to the southern area of Chinle/Dockum deposition but instead was widespread across the paleoriver systems of the Late Triassic in western Pangea. The specimen we report on here was found in close association with a typical Late Triassic Chinle fauna, including phytosaurs, metoposaurs, and dinosauromorphs.





PalZ ◽  
1991 ◽  
Vol 65 (1-2) ◽  
pp. 191-198 ◽  
Author(s):  
Adrian P. Hunt ◽  
Spencer G. Lucas
Keyword(s):  


2008 ◽  
Vol 276 (1656) ◽  
pp. 507-513 ◽  
Author(s):  
Walter G Joyce ◽  
Spencer G Lucas ◽  
Torsten M Scheyer ◽  
Andrew B Heckert ◽  
Adrian P Hunt

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.



2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Axel Hégron ◽  
Michelle R. Stocker ◽  
Adam D. Marsh ◽  
Sterling J. Nesbitt
Keyword(s):  


2016 ◽  
Vol 225 ◽  
pp. 106-131 ◽  
Author(s):  
Sofie Lindström ◽  
Randall B. Irmis ◽  
Jessica H. Whiteside ◽  
Nathan D. Smith ◽  
Sterling J. Nesbitt ◽  
...  


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