Parrishia
Encyclopedia
Parrishia is an extinct genus
of sphenosuchia
n crocodylomorph that is currently considered a nomen dubium
because of the lack of diagnostic features associated with it. Fossils are known from the Chinle
, Dockum
, and Santa Rosa Formation
s in Arizona
and New Mexico
.
The genus was named in 1995 from fossils found from the Placerias quarry of the Chinle Group in Apache County, Arizona
. 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. However, new 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. 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. Therefore, the only distinguishing character that distinguishes Parrishia from Hesperosuchus is the robustness of the vertebrae. Material from Parrishia cannot currently be assigned to any other known sphenosuchian genus because of the lack of postcranial apomorphies; as a result, it is considered an indeterminate genus.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of sphenosuchia
Sphenosuchia
Sphenosuchia is a suborder of basal crocodylomorphs that first appeared in the Triassic and occurred into the Late Jurassic. Most were small, gracile animals with an erect limb posture. They are now thought to be ancestral to crocodyliforms, which include all living crocodilians.-Stratigraphic...
n crocodylomorph that is currently considered a nomen dubium
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
because of the lack of diagnostic features associated with it. Fossils are known from the Chinle
Chinle Formation
The Chinle is a geologic formation that is spread across the U.S. states of northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Chinle is controversially considered to be synonymous to the Dockum Group in eastern Colorado, eastern New Mexico, southwestern Kansas, the...
, Dockum
Dockum Group
The Dockum is a Late Triassic geologic group found primarily on the Llano Estacado of western Texas and eastern New Mexico with minor exposures in southwestern Kansas, eastern Colorado, and Oklahoma panhandle. The Dockum reaches a maximum thickness of slightly over 650 m but is usually much...
, and Santa Rosa Formation
Dockum Group
The Dockum is a Late Triassic geologic group found primarily on the Llano Estacado of western Texas and eastern New Mexico with minor exposures in southwestern Kansas, eastern Colorado, and Oklahoma panhandle. The Dockum reaches a maximum thickness of slightly over 650 m but is usually much...
s in Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
and New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
.
The genus was named in 1995 from fossils found from the Placerias quarry of the Chinle Group in Apache County, Arizona
Apache County, Arizona
-2010:Whereas according to the 2010 U.S. Census Bureau:*23.3% White*0.2% Black*72.9% Native American*0.3% Asian*0.0% Native Hawaiian or Pacific Islander*2.0% Two or more races*1.3% Other races*5.8% Hispanic or Latino -2000:...
. It was named after the paleontologist J. Michael Parrish, with the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
being P. mccreai. Parrishia was distinguished from the closely related genus Hesperosuchus
Hesperosuchus
Hesperosuchus is an extinct genus of crocodylomorph reptile that contains a single species, Hesperosuchus agilis. Remains of this sphenosuchian have been found in Late Triassic strata from Arizona and New Mexico....
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. However, new 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. 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. Therefore, the only distinguishing character that distinguishes Parrishia from Hesperosuchus is the robustness of the vertebrae. Material from Parrishia cannot currently be assigned to any other known sphenosuchian genus because of the lack of postcranial apomorphies; as a result, it is considered an indeterminate genus.