21st August 2013
Mike Taylor1 & Mathew Wedel2
1University of Bristol, Bristol, UK.
2Western University of Health Sciences, Pomona, USA.
The sauropod dinosaur Barosaurus lentus, from the Upper Jurassic Morrison Formation of the western United States, is a regular in popular dinosaur books. It is invariably illustrated and described as virtually identical to Diplodocus but with a proportionally longer neck. It has even been suggested that that Barosaurus and Diplodocus are sexual dimorphs. This popular interpretation of Barosaurus is based primarily on the referred specimen AMNH 6341. However, its cervical vertebrae do not closely resemble those of the holotype YPM 429. The best-preserved of the type vertebrae is a posterior cervical designated 'R', probably C14. This vertebra resembles those of brachiosaurids more than those of diplodocids: the neural arch is set forwards on the centrum, the articular surfaces are anteriorly inclined, and the neural spine seems to be unsplit, with the spinozygapophyseal laminae forming a diagonal cross in dorsal view and converging to a low point. The vertebra also has unique features, notably its extremely broad, wing-like, prezygapophyseal rami. The situation is further confused by other referred Barosaurus specimens, including CM 1198, CM 11984, ROM 3670 and two separate juvenile individuals, probably belonging to two different taxa but catalogued together as AMNH 7535. These specimens, together with Kaatedocus, may form a morphological sequence between Diplodocus and the popular conception of 'Barosaurus'; but YPM 429 seems distinct from them all. This complex situation emphasises that the diversity of Morrison Formation sauropods is still far from being resolved. New taxa continue to be named, more await description, and even well-known taxa conceal cryptic diversity.
[Note: much of what I said in this talk contradicts what is written in this abstract, which therefore should not be cited. In particular, the title of the actual talk was "Barosaurus revisited: the concept of Barosaurus (Dinosauria: Sauropoda) is not based on erroneously referred specimens".]
The abstracts volume for SVPCA 2013 can be downloaded.