Parrishia

Parrishia is an extinct genus of sphenosuchian crocodylomorph known from the Late Triassic Chinle, Dockum, and Santa Rosa Formations in Arizona and New Mexico.

Parrishia Temporal range: Late Triassic 221.5–205.6 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauria
Clade:	Pseudosuchia
Clade:	Crocodylomorpha
Genus:	†Parrishia Long and Murry, 1995
Type species
†P. mccreai Long and Murry, 1995

Discovery and naming

The genus was named in 1995 from fossils found from the Placerias quarry of the Chinle Group in Apache County, Arizona.^[1] It was named after the paleontologist J. Michael Parrish, with the type species being P. mccreai. Parrishia was distinguished from the closely related genus Hesperosuchus on the basis of more robust vertebral centra and the lack of dorsoventrally offset articular faces of the cervical centra, thus causing the neck to be straight rather than anterodorsally curved as in Hesperosuchus.^[1]

In their description of a new crocodylomorph skeleton from the famous Whitaker quarry in Ghost Ranch, Clark et al. (2000) treated Parrishia as a nomen dubium because they considered the holotype and referred specimens undiagnostic.^[2] More complete postcranial skeletons such as PEFO 26681 have been found that clearly show that the cervical centra of Parrishia possess articular faces that are dorsoventrally offset as in Hesperosuchus.^[3] Additionally, in the holotype specimen (UCMP A269/139623) the anterior surfaces of the centa are positioned more dorsally than the posterior surfaces, giving the neck an anterodorsal curve like Hesperosuchus.^[2][4] Therefore, the only distinguishing character that distinguishes Parrishia from Hesperosuchus is the robustness of the vertebrae.^[3] Material from Parrishia cannot be assigned to any other known sphenosuchian genus because of the lack of postcranial apomorphies; as a result, it is considered an indeterminate genus.^[5]

In an SVP 2018 conference abstract, William Parker and colleagues reported the discovery of new specimens indicating that Parrishia represents a phytosaur and not a crocodylomorph.^[6]

References

1. Long, R. A.; Murry, P. A. (1995). "Late Triassic (Carnian and Norian) tetrapods from the southwestern United States". New Mexico Museum of Natural History and Science Bulletin. 4: 1–254.
2. Clark, J. M.; Sues, H.-D.; Berman, D. S. (2000). "A new specimen of Hesperosuchus agilis from the Upper Triassic of New Mexico and the interrelationships of basal crocodylomorph archosaurs". Journal of Vertebrate Paleontology. 20 (4): 683–704. doi:10.1671/0272-4634(2000)020[0683:ANSOHA]2.0.CO;2. S2CID 7455338.
3. Parker, W. G.; Irmis, R. B. (2005). "Advances in Late Triassic vertebrate paleontology based on new material from Petrified Forest National Park, Arizona". In Heckert, A. B.; Lucas, S. G. (eds.). Vertebrate Paleontology in Arizona. New Mexico Museum of Natural History and Science Bulletin. Vol. 29. Albuquerque, New Mexico: New Mexico Museum of Natural History and Science. pp. 45–58.
4. Colbert, E. H. (1952). "A pseudosuchian reptile from Arizona". Bulletin of the American Museum of Natural History. 99: 561–592.
5. Irmis, R. B. (2005). "The vertebrate fauna of the Upper Triassic Chinle Formation in Northern Arizona". In Sterling J. Nesbitt; William G. Parker; Randall B. Irmis (eds.). Guidebook to the Triassic Formations of the Colorado Plateau in Northern Arizona: Geology, Paleontology, and History. Vol. 9. Bulletin of the Mesa Southwest Museum.
6. "Program booklet". vertpaleo.org. 2018. Retrieved 2020-02-06.