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Temporal range: Late Jurassic, 154Ma
Eobrontosaurus yahnahpin.jpg
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Suborder: Sauropodomorpha
Family: Diplodocidae
Subfamily: Apatosaurinae
Genus: Eobrontosaurus
Bakker, 1998
Species: E. yahnahpin
(Filla & Redman, 1994) [originally Apatosaurus]

Eobrontosaurus (meaning "dawn thunder lizard") is the name given to a genus of dinosaur from the Late Jurassic of North America. It was a sauropod probably closely related to Apatosaurus. It is known from a single site from the lower Morrison Formation, dating to about 154 million years ago.[1] It grew up to 21 metres (69 ft) long.[2]

The type species, E. yahnahpin, was described by James Filla and Patrick Redman in 1994 as a species of Apatosaurus (A. yahnahpin).[3] The specific name is derived from Lakota mah-koo yah-nah-pin, "breast necklace", a reference to the pairs of sternal ribs that resemble the hair pipes traditionally worn by the tribe. The holotype is TATE-001, a relatively complete postcranial skeleton found in Wyoming, in the lower Morrison Formation. More fragmentary remains have also been referred to the species.

A re-evaluation by Robert T. Bakker in 1998 found it to be more primitive, and so Bakker coined the new generic name Eobrontosaurus, derived from Greek eos, "dawn", and Brontosaurus, the original generic name of Apatosaurus excelsus.[4] It has been argued that Eobrontosaurus yahnahpin actually belongs within Camarasaurus,[5] although this has been questioned.[6][2] According to Bakker Eobrontosaurus was a member of the Diplodocidae, more specifically the Apatosaurinae.


  1. ^ Turner, C.E. and Peterson, F., (1999). "Biostratigraphy of dinosaurs in the Upper Jurassic Morrison Formation of the Western Interior, U.S.A." Pp. 77–114 in Gillette, D.D. (ed.), Vertebrate Paleontology in Utah. Utah Geological Survey Miscellaneous Publication 99-1.
  2. ^ a b Holtz, Thomas R. Jr. (2011) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2010 Appendix.
  3. ^ Filla, J.A., Redman, P.D. (1994). "Apatosaurus yahnahpin: a preliminary description of a new species of diplodocid dinosaur from the Late Jurassic Morrison Formation (Kimmeridgian-Portlandian) and Cloverly Formation (Aptian-Albian) of the western United States", Mémoires de la Société Géologique de France (Nouvelle Série) 139 (Ecosystèmes Continentaux du Mésozoique): 87-93
  4. ^ Bakker, R.T. (1998). "Dinosaur mid-life crisis: the Jurassic-Cretaceous transition in Wyoming and Colorado". In: S.G. Lucas, J.I. Kirkland, & J.W. Estep (eds.) Lower and Middle Cretaceous Terrestrial Ecosystems; New Mexico Museum of Natural History and Science Bulletin, 14: 67–77.
  5. ^ Upchurch, P., Barrett, P.M. and Dodson, P. (2004). "Sauropoda". In Weishampel, D.B., Osmólska, H., and Dodson, P. (eds.), The Dinosauria (2nd edition). University of California Press, Berkeley 259-322.
  6. ^ Hartman, Scott (2005-02-13). ""Eobrontosaurus" is not Camarasaurus". The Dinosaur Mailing List Archives. Retrieved 27 January 2010.