Caseosaurus

Caseosaurus; Temporal range: Norian, ; 221.5–212 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	Holotype ilium in lateral and medial view
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Genus:	†Caseosaurus; Hunt et al., 1998
Type species
	†Caseosaurus crosbyensis; Hunt et al., 1998

Caseosaurus (/ˌkeɪzioʊˈsɔːrəs/ KAY-zee-oh-SOR-əs) is a genus of saurischian dinosaur that lived approximately 221.5 to 212 million years ago during the latter part of the Triassic Period in what is now Texas, North America. It was a small, lightly-built, bipedal, ground-dwelling carnivore, and could grow up to 2 m (6.6 ft) long.

Description

The genus Caseosaurus, is known from specimen UMMP 8870, an isolated hip bone measuring nearly 141 mm. A 3D model of this specimen is available on the University of Michigan Online Repository of Fossils. Size estimates suggest that Caseosaurus was up to 2 m (6.6 ft) long and weighed up to 50 kilograms (110.2 pounds) at most.^[1]

Discovery

The genus name Caseosaurus means "Case's lizard", and was named in honor of the scientist who discovered it, Ermine Cowles Case. The suffix "-saurus" Greek(σαυρος) means "lizard".^[2] The specific name crosbyensis, is a Latinized rendering of Crosby County in Texas, the site of its discovery. Caseosaurus was described, and named by A. P. Hunt, Spencer G. Lucas, Andrew B. Heckert, Robert M. Sullivan, and Martin Lockley in 1998, with the type species being Caseosaurus crosbyensis.^[3]

Classification

In 1998, Hunt et al., examined UMMP 8870, a partial hip bone (ilium) originally assigned as a paratype of the dinosaur Chindesaurus, and designated it as the holotype of a new dinosaur, Caseosaurus crosbyensis. Irmis et al. concluded that an ilium, NMMNH P-35995 originally assigned by Heckert et al. in 2000 to the silesaurid Eucoelophysis, strongly resembles the Caseosaurus holotype.^[4] Langer (2004) examined the ilium and reassigned it back to the genus Chindesaurus.^[5]

However, in 2018, Caseosaurus was considered a valid species, and was identified as a relative of Herrerasaurus, outside of the Dinosauria.^[6]

Distinguishing anatomical features

According to Baron and Williams (2018), Caseosaurus can be distinguished from all dinosaurs (including herrerasaurids, which are placed outside Dinosauria in their analysis) by a distinctive feature: a sharp, well developed ridge connects the midpoint of the supracetabular crest to the preacetabular process.^[6] However, a recent review of early South American dinosaurs has classified it as a nomen dubium without addressing the previous study.^[7]

Paleoecology

The only specimen of Caseosaurus was discovered in the Tecovas Formation of the Dockum Group in Texas, within sediments deposited during the Norian stage of the Late Triassic period, approximately 221.5 to 212 million years ago. The paleonvironment of Caseosaurus's included the archosaur Tecovasaurus and other early theropod dinosaurs, some of which left preserved bipedal tracks.

References

^ "CASEOSAURUS". Dinochecker.com. Retrieved 2 July 2013.
^ Liddell, Henry George and Robert Scott (1980). A Greek-English Lexicon (Abridged ed.). United Kingdom: Oxford University Press. ISBN 978-0-19-910207-5.
^ 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.
^ Irmis, Nesbitt, Padian, Smith, Turner, Woody and Downs, 2007. A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science. 317, 358-361.
^ Langer, 2004. Basal Saurischia. In Weishampel, Dodson and Osmolska. The Dinosauria Second Edition. University of California Press. 861 pp.
^ ^a ^b Matthew G. Baron; Megan E. Williams (2018). "A re-evaluation of the enigmatic dinosauriform Caseosaurus crosbyensis from the Late Triassic of Texas, USA and its implications for early dinosaur evolution". Acta Palaeontologica Polonica. 63. doi:10.4202/app.00372.2017.
^ Novas, Fernando E.; Agnolin, Federico L.; Ezcurra, Martín D.; Temp Müller, Rodrigo; Martinelli, Agustín G.; Langer, Max C. (October 2021). "Review of the fossil record of early dinosaurs from South America, and its phylogenetic implications". Journal of South American Earth Sciences. 110: 103341. doi:10.1016/j.jsames.2021.103341. ISSN 0895-9811.

External links

Texas Dinosaurs from Texas A&M University

[1] "CASEOSAURUS". Dinochecker.com. Retrieved 2 July 2013.

[Liddell_1980-2] Liddell, Henry George and Robert Scott (1980). A Greek-English Lexicon (Abridged ed.). United Kingdom: Oxford University Press. ISBN 978-0-19-910207-5.

[hunt98-3] 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.

[4] Irmis, Nesbitt, Padian, Smith, Turner, Woody and Downs, 2007. A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science. 317, 358-361.

[5] Langer, 2004. Basal Saurischia. In Weishampel, Dodson and Osmolska. The Dinosauria Second Edition. University of California Press. 861 pp.

[:0-6] Matthew G. Baron; Megan E. Williams (2018). "A re-evaluation of the enigmatic dinosauriform Caseosaurus crosbyensis from the Late Triassic of Texas, USA and its implications for early dinosaur evolution". Acta Palaeontologica Polonica. 63. doi:10.4202/app.00372.2017.

[7] Novas, Fernando E.; Agnolin, Federico L.; Ezcurra, Martín D.; Temp Müller, Rodrigo; Martinelli, Agustín G.; Langer, Max C. (October 2021). "Review of the fossil record of early dinosaurs from South America, and its phylogenetic implications". Journal of South American Earth Sciences. 110: 103341. doi:10.1016/j.jsames.2021.103341. ISSN 0895-9811.

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