Genus: Caseosaurus Hunt, Lucas, Heckert , Sullivan , and Lockley, 1998

Classification: Dinosauria - Saurischia - Theropoda - Herrerasauria

Etymology: In recognition of E. C. Case who discovered the holotype and made substantial contributions to our knowledge of late Triassic tetrapods.

Synonyms: none

Type species: Hunt, Lucas, Heckert , Sullivan , and Lockley, 1998

Other Species: none

Diagnosis:

Species: C. crosbyensis Hunt, Lucas, Heckert , Sullivan , and Lockley, 1998

Etymology: In reference to Crosby County, Texas which yielded the holotype

Synonyms:

Holotype: UMMP 8870: Right ilium.

Referred Specimens: = cf. Caseosaurus crosbyensis Nesbitt, Irmis, and Parker, 2007
Near Ghost Ranch, Rio Arriba County, New Mexico, USA.
Petrified Forest Formation, Chinle Group.
Early Norian, Late Triassic.
NMMNH P-35995: Partial ilium.

Time: Carnian, Late Triassic.

Horizon: Tecovas Member, Dockum Formation.

Location: Crosby County, exact locality unknown, Texas, USA.

Total length:

Mass:

Diagnosis: Herrerasaur whose ilium differs from Staurikosaurus and Herrerasaurus in possessing: (1) an elongate and dorsoventrally narrow posterior blade; (2) a narrow ridge on the l a t e r a l margin that extends from the anterodorsal margin of the acetabulum to the anterodorsal anterior spine; (3) a highly reduced brevis fossa; and (4) a semicircular margin dorsal to the acetabulum; differs from Chindesaurus bryansmalli in possessing a less deep brevis shelf which does not extend to the posterior margin, a l a t e r a l longitudinal ridge (for sacral rib a r t i c u l a t i o n ) which is placed more ventrally and a much thinner (less than half) posterior blade in dorsal view (Hunt, Lucas, Heckert, Sullivan & Lockley, 1998).

Comments: Case (1927) described an isolated dinosaur ilium (UMMP 8870) from the Tecovas Member that Long assigned to the herrerasaurid Chindesaurus bryansmalli. This specimen bears a strong resemblance to the corresponding element in Staurikosaurus and Herrerasaurus in being anteroposteriorly short and dorsoventrally high with a partially perforate acetabulum. Specifically, UMMP 8870 represents a dinosaur because it has a brevis shelf and a medially opened acetabular wall. Further, it represents a herrerasaur because the brevis shelf is reduced to a slight ridge, and the brevis fossa is small. UMMP 8870 differs from Staurikosaurus and Herrerasaurus in possessing: (1) an elongate and dorsoventrally narrow posterior blade; (2) a narrow ridge on the lateral margin that extends from the anterodorsal margin of the acetabulum to the anterodorsal anterior spine; (3) a highly reduced brevis fossa; and (4) a semicircular margin dorsal to the acetabulum. Long (in Murry, 1989; Long & Murry 1995) assigned UMMP 8870 to Chindesaurus bryansmalli. The holotype of Chindesaurus (PEFO 10395) includes only two small fragments of the ilium, that Long and Murry (1995) consider to be indistinguishable from UMMP 8870 - a fragment of the pubic process of the left ilium and a portion of the left posterior iliac blade.
The pubic process possesses no diagnostic characters but the iliac blade fragment can be directly compared to the Texas ilium. The posterior iliac blade of PEFO 10395 differs from that in UMMP 8870 in possessing a deep brevis shelf that extends to the posterior margin, a lateral longitudinal ridge (for sacral rib articulation) that is placed more dorsally and a much thicker (more than twice) posterior blade in dorsal view. It is clear that the Texas specimen represents a herrerasaurid, but that it cannot be referred t Chindesaurus or any other described member of this family (Hunt, Lucas, Heckert, Sullivan & Lockley, 1998).

Illustrations:

Holotype ilium of Caseosaurus crosbyensis (UMMP 8870) in lateral (1) and medial (2) views (after Case 1927). Scale bar is 5 cm.

References:

Long, R. A., and Murry P. A., 1995, Late Triassic (Carnian and Norian) Tetrapods from the Southwestern United States: New Mexico Museum of Natural History & Science, A Division of the Office of Cultural Affairs, Bulletin 4, p. 1-254.

Hunt, A. P., Lucas S. G., Heckert A. B., Sullivan R. M., and Lockley M. G., 1998, Late Triassic Dinosaurs from the Western United States: Geobios, v. 31, n. 4, p. 511-531.

Nesbitt, S. J., Irmis, R. B., and Parker, W. G., 2007, A critical re-evaluation of the Late Triassic Dinosaur Taxa of North America: Journal of Systematic Palaeontology, v. 5, n. 2, p. 209-243.

© Tetrapoda Database Roman Ulansky roman.ulansky@gmail.com or adios85@mail.ru