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Caseosaurus crosbyensis

Osteichthyes

Taxonomy
Caseosaurus crosbyensis was named by Hunt et al. (1998). Its type specimen is UMMP 8870, a set of postcrania (ilium), and it is a 3D body fossil. Its type locality is west bank of Blanco River, northern breaks, which is in a Carnian/Norian terrestrial claystone in the Tecovas Formation of Texas. It is the type species of Caseosaurus.

It was synonymized subjectively with Chindesaurus bryansmalli by Langer (2004).

Synonymy list
YearName and author
1998Caseosaurus crosbyensis Hunt et al. p. 530 fig. 3
2007Caseosaurus crosbyensis Nesbitt et al. pp. 225-226
2009Caseosaurus crosbyensis Bittencourt and Kellner p. 30
2010Caseosaurus crosbyensis Langer et al. p. 71
2018Caseosaurus crosbyensis Baron and Williams pp. 135-136
2021Caseosaurus crosbyensis Müller and Garcia p. 9

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RankNameAuthor
kingdomAnimalia()
Bilateria
EubilateriaAx 1987
Deuterostomia
phylumChordataHaeckel 1874
subphylumVertebrata
superclassGnathostomata
classOsteichthyes
subclassSarcopterygii()
subclassDipnotetrapodomorpha(Nelson 2006)
subclassTetrapodomorpha()
Tetrapoda
Reptiliomorpha
Anthracosauria
subclassAmphibiosauriaKuhn 1967
Cotylosauria()
RankNameAuthor
Amniota
Sauropsida
classReptilia
subclassEureptilia()
Romeriida
Diapsida()
Archosauromorpha(Huene 1946)
Crocopoda
ArchosauriformesGauthier 1986
Eucrocopoda
Archosauria()
superorderTheropodomorpha
infraorderHerrerasauria
genusCaseosaurus
speciescrosbyensis

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

Caseosaurus crosbyensis Hunt et al. 1998
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Diagnosis
ReferenceDiagnosis
A. P. Hunt et al. 1998As for genus.
M. G. Baron and M. Williams 2018Caseosaurus crosbyensis represents a valid taxon and a most likely represents a member of the clade Herrerasauria. Caseosaurus crosbyensis is unique among herrerasaurids and dinosaurs in possessing of the supraacetabular crest to the preacetabular process. Furthermore, Caseosaurus crosbyensis can be referred to Herrerasauria based upon the possession of three of the clade’s synapomorphies: a postacetabular process that is 25–35% of the total length of the length of the iliac blade and a supraacetabular crest that extends down part of pubic peduncle as a ridge without reaching the distal end*; possession of extensive rugosities on the pre- and postacetabular processes* (also present in a similar form in silesaurids, and in a slightly different form in Saturnalia tupiniquim and Coelophysis bauri). In addition to these features, Caseosaurus crosbyensis possesses a number of other features that can be observed in all other herrerasaurs,including: a preacetabular process of the ilium that expands mediolaterally towards its distal end* (also in silesaurids); absence of a brevis fossa. Furthermore, Caseosaurus crosbyensis and NMMNH P-35995 possess an ischiadic peduncle that is less ventrally extensive than the pubic peduncle in medial and lateral aspect, a condition that is also present in Herrerasaurus ischigualastensis and Staurikosaurus pricei. Caseosaurus crosbyensis can be distinguished from Herrerasaurus ischigualastensis and Staurikosaurus pricei by possessing a preacetabular process that is more than twice as long as it is deep*; having a sharp, distinct anterodorsal ridge that runs from the middle of the supraacetabular crest to the preacetabular process*; and the absence of an acetabular antitrochanter* (which also distinguishes Caseosaurus crosbyensis from Chindesaurus bryansmalli). Caseosaurus crosbyensis can be further distinguished from Staurikosaurus pricei as it possesses a preacetabular iliac process that is much shorter than the postacetabular process of the ilium (also present in Herrerasaurus ischigualastensis, Eoraptor lunensis, and Eodromaeus murphi). Further to these distinguishing features, Caseosaurus crosbyensis appears to differ from other herrerasaurs in a several other respects. For example, while Caseosaurus crosbyensis possesses rugose areas on the dorsal and lateral portions of the pre- and postacetabular processes, these areas are less extensive than they are in Herrerasaurus ischigualastensis and Staurikosaurus pricei (Fig. 6). Furthermore, the supracetabular crest of Caseosaurus crosbyensis describes a semicircle in lateral view*, differing from the condition in Herrerasaurus ischigualastensis and Staurikosaurus pricei, in which the supraacetabular crest is not semicircular but instead forms a straighter, anteroventrally oriented lip over the main body of the acetabulum (Fig. 6). For the anatomical features listed above, (*) represents those that are present in both the holotype and the referred specimen of Caseosaurus crosbyensis; the single autapomorphy of the taxon is also observed in both specimens.