Bistahieversor

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Bistahieversor
Temporal range: Late Cretaceous, 74.5Ma
New Mexico Museum of natural History and science
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Theropoda
Family: Tyrannosauridae
Subfamily: Tyrannosaurinae
Genus: Bistahieversor
Carr & Williamson, 2010
Species: † B. sealeyi
Binomial name
Bistahieversor sealeyi
Carr & Williamson, 2010

Bistahieversor (meaning "Bistahi destroyer") is a genus of tyrannosaurid dinosaur. Bistahieversor existed in the Late Cretaceous[1] Hunter Wash member of the Kirtland Formation, which has been dated to 74.55 ± 0.29 Ma.[2]

The name Bistahieversor comes from the Navajo Bistahí, or "place of the adobe formations" in reference to the Bisti/De-Na-Zin Wilderness where it was found, and eversor, meaning "destroyer."[1]

Description[edit]

Size comparison with a juvenile
Wall-mounted fossil

Material from both adolescent and adult individuals has been found in the Kirtland Formation of New Mexico, United States. Adult Bistahieversor are estimated to have been around 9 metres (30 ft) long, weighing at least a ton. The snout is deep, indicating that the feature is not unique to more derived tyrannosaurs such as Tyrannosaurus. Geographical barriers such as the newly forming Rocky Mountains may have isolated the more southerly Bistahieversor from more derived northern tyrannosaurs.[3]

Bistahieversor differs from other tyrannosaurs in the possession of 64 teeth, an extra opening above the eye, and a keel along the lower jaw. The opening above the eye is thought to have accommodated an air sac that would have lightened the skull's weight. Bistahieversor also had a complex joint at its "forehead" that would have stabilized the skull, preventing movement at the joint.[4]

History of discovery[edit]

The first remains now attributed to Bistahieversor, a partial skull and skeleton, were described in 1990 as a specimen of Aublysodon.[5] Additional remains, consisting of the incomplete skull and skeleton of a juvenile, were described in 1992.[6] Another, complete, skull and partial skeleton were found in the Bisti/De-Na-Zin Wilderness of New Mexico in 1998.[7] In a 2000 paper, Thomas Carr and Thomas Williamson re-examined these four specimens and suggested that they did not belong to Aublysodon, but rather to one or more new species of Daspletosaurus.[8] However, it was not until 2010 that Carr and Williamson published a thorough re-description of the specimens and found that they belonged to a new genus and species of more generalized tyrannosauroid, which they named Bistahieversor sealeyi.[1]

Classification[edit]

Bistahieversor is a genus of derived dinosaur currently classified in the subfamily Tyrannosaurinae. It is more derived than Teratophoneus but less derived than Lythronax. It forms a clade of tyrannosaurines with Lythronax, Tyrannosaurus, Tarbosaurus and Zhuchengtyrannus.[9]

Restoration
A skull during preparation

Below is a cladogram by Loewen et al. in 2013.[9]

Tyrannosaurinae

Dinosaur Park Fm. tyrannosaurid B




Daspletosaurus




Two Medicine Fm. tyrannosaurid




Teratophoneus




Bistahieversor




Lythronax




Tyrannosaurus




Tarbosaurus



Zhuchengtyrannus










See also[edit]

References[edit]

  1. ^ a b c Carr, T.D. and Williamson, T.E. (2010). "Bistahieversor sealeyi, gen. et sp. nov., a new tyrannosauroid from New Mexico and the origin of deep snouts in Tyrannosauroidea." Journal of Vertebrate Paleontology, 30(1): 1-16. doi:10.1080/02724630903413032
  2. ^ Sullivan, R.M., and Lucas, S.G. 2006. "The Kirtlandian land-vertebrate "age" – faunal composition, temporal position and biostratigraphic correlation in the nonmarine Upper Cretaceous of western North America." New Mexico Museum of Natural History and Science, Bulletin 35:7-29.
  3. ^ Rettner, R. (28 January 2010). "New Tyrannosaur Species Discovered". LiveScience. Retrieved 1 February 2010. 
  4. ^ Viegas, J. (28 January 2010). "New Tyrannosaur Had More Teeth Than T. rex". Discovery News. Retrieved 1 February 2010. 
  5. ^ Lehman and Carpenter, K. (1990). "A partial skeleton of the tyrannosaurid dinosaur Aublysodon from the Upper Cretaceous of New Mexico." Journal of Paleontology, 64: 1026-1032.
  6. ^ Archer, B. and Babiarz, J.P. (1992). "Another tyrannosaurid dinosaur from the Cretaceous of northwest New Mexico." Journal of Paleontology, 66: 690–691.
  7. ^ "New Species of Tyrannosaur Discovered in Southwestern U.S.". Newswise. 28 January 2010. Retrieved 1 February 2010. 
  8. ^ Carr, T. D. and Williamson, T.E. (2000). "A review of Tyrannosauridae (Dinosauria: Coelurosauria) from New Mexico." New Mexico Museum of Natural History and Science Bulletin, 17: 113–145.
  9. ^ a b Loewen, M. A.; Irmis, R. B.; Sertich, J. J. W.; Currie, P. J.; Sampson, S. D. (2013). "Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans". In Evans, David C. PLoS ONE 8 (11): e79420. doi:10.1371/journal.pone.0079420.  edit