(Dawn thunder lizard).
Named By: Robert T. Bakker - 1998.
Synonyms: Apatosaurus yahnahpin.
Classification: Chordata, Reptilia, Dinosauria, Saurischia, Sauropodomorpha, Sauropoda, Diplodocidae, Apatosaurinae.
Species: E. yahnahpin (type).
Size: 21 meters long.
Known locations: USA, Wyoming - Morrison Formation.
Time period: Kimmeridgian to Tithonian of the Jurassic.
Fossil representation: Almost complete post cranial skeleton as well as additional fragmentary remains.
was initially described as a new species of Apatosaurus
yahnahpin by James Filla and Patrick Redman in 1994.
the material was re-examined by Robert Bakker in 1998 he found that
it represented a similar but more primitive sauropod
dinosaur to Apatosaurus.
The second species of Apatosaurus, A.
by the name of Brontosaurus excelsus until it was
declared to be a
synonym to the earlier Apatosaurus by Elmer S.
Riggs in 1903.
This is a clearly definable species to the Apatosaurus
type species of
A. ajax, and in the 1990s Bakker suggested
that A. excelsus is
different enough to resurrect Brontosaurus as its
own genus, although
this was largely refuted by other palaeontologists and to this day
Brontosaurus is still a synonym to Apatosaurus.
This is in part why
Bakkar chose the name Eobrontosaurus instead of Eoapatosaurus,
although it does also help prevent confusion with the Apatosaurus
Suggestions have been made that Eobrontosaurus may actually be a specimen of Camarasaurus, although most palaeontologists do not accept this idea.
- 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. - J. A. Filla & P. D. Redman - 1994.
- Dinosaur mid-life crisis: the Jurassic-Cretaceous transition in Wyoming and Colorado. - Lower and Middle Cretaceous Terrestrial Ecosystems, New Mexico Museum of Natural History and Science Bulletin 14:67-77 - R. T. Bakker - 1998.