Chindesaurus

Chindesaurus Temporal range: Late Triassic, 216 Ma PreЄ Є O S D C P T J K Pg N ↓
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	Dinosauria
Order:	Saurischia
Family:	Herrerasauridae?
Genus:	Chindesaurus Long & Murry, 1995
Species
C. bryansmalli Long & Murry, 1995 (type)
Synonyms
?Caseosaurus Hunt et al., 1998

Chindesaurus ( /ˌtʃɪndɨˈsɔrəs/ chin-di-sawr-əs; meaning "Lizard from Chinde Point) is a genus of saurischian dinosaur named after Chinde Point (Chinde {Navajo, chindi} meaning "ghost or evil spirit"), near where the genoholotype specimen (a partial skeleton) was discovered in the Chinle Formation of Petrified Forest National Park, Arizona, by Bryan Small in 1985.^[1] The Petrified Forest formation dates to the early Norian stage of the late Triassic period, about 216 million years ago.^[2] It was formally described by Long and Murry in 1995. The type species, Chindesaurus bryansmalli, is named in honor of the discoverer.

Description

Chindesaurus is known from five incomplete specimens (six if Caseosaurus is included). The type specimen is the most complete, and contains several rib and vertebrae fragments, two complete vertebrae from the hips and one from the tail, fragments of hip bones, and partial leg bones. A single tooth was also found with the specimen.^[3] The remaining specimens are even more incomplete, consisting of isolated hip bones and upper leg bones (femora), and more vertebrae.

The type and paratype specimens probably came from individuals around 2.4 metres (7.9 ft) in length.

Classification

Chindesaurus has been difficult to classify, and has been recovered in several different positions at the base of the saurischian family tree. When it was first discovered in 1985, the animal which would eventually be named Chindesaurus was thought to be a prosauropod.^[4] When it was finally described and named a decade after its discovery by Long and Murray, they regarded it as a herrerasaurid, an opinion that has been followed by most paleontologists since.^[3] Phylogenetic analyses published through 2007 continued to find it to fall among the herrerasaurids,^[5][6] though a few studies cast doubt on this, including one in 2007 by Irmis, Nesbitt and colleagues which found Chindesaurus to be a probable basal saurischian dinosaur, and noted that it shares a wide range of characteristics with several lineages of basal saurischians, making any classification problematic.^[7]

One specimen originally assigned to Chindesaurus, from the Tecovas Formation of Texas, was later placed in its own genus and species, Caseosaurus crosbyensis.^[8] Subsequent research has shown that this separation was probably in error, and that the two forms represent the same species.^[9] Nesbitt, Irmis and Parker agreed in a 2007 paper that there is little reason to separate Caseosaurus from Chindesaurus, and the two even share some unique characteristics not found in similar species. Nesbitt and colleagues suggested that any differences between the two were probably related to differences in size. However, since both species are so fragmentary, they decided not to formally make them synonyms.^[10]

References

1. ^ Parker, W. G., R. B. Irmis, and S. J. Nesbitt. 2006. Review of the Late Triassic dinosaur record from Petrified Forest National Park . Pages 160-161 in Parker, W. G., S. R. Ash, and R. B. Irmis, editors. A century of research at Petrified Forest National Park: geology and paleontology. Museum of Northern Arizona, Flagstaff, Arizona. Bulletin 62.
2. ^ Litwin, R.J., Traverse, A., and Ash, S.R., 1991. Preliminary palynological zonation of the Chinle Formation, southwestern U.S.A., and its correlation to the Newark Supergroup (eastern U.S.A.). Review of Paleobotany and Palynology, v. 77, p. 269-287.
3. ^ ^{a b} Long and Murry, (1995). "Late Triassic (Carnian and Norian) tetrapods from the Southwestern United States." New Mexico Museum Natural History Science Bulletin, 4: 1-254.
4. ^ Meyer, (1986). "D-Day on the Painted Desert." Arizona Highways, 62(7): 3-13.
5. ^ Bittencourt and Kellner, (2004). "The phylogenetic position of Staurikosaurus pricei Colbert, 1970 from the Triassic of Brazil." Journal of Vertebrate Paleontology, 24(3):.
6. ^ 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.
7. ^ Irmis, R.B., Nesbitt, S.J., Padian, K., Smith, N.D., Turner, A.H., Woody, D.T., and Downs, A. (2007). "A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs". Science 317: 358-361
8. ^ Hunt, Lucas, Heckert, Sullivan and Lockley, (1998). "Late Triassic Dinosaurs from the Western United States." Geobios, 31(4): 511-531.
9. ^ Langer, (2004). "Basal Saurischia." In Weishampel, Dodson and Osmolska (eds.). The Dinosauria Second Edition. University of California Press. 861 pp.
10. ^ Nesbitt, Irmis and Parker, (2007). "A critical re-evaluation of the Late Triassic dinosaur taxa of North America." Journal of Systematic Palaeontology, 5(2): 209–243.

External links

• Image of Chindesaurus by Rob Gay

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