Geological Magazine



Original Article

A saurischian dinosaur braincase from the Middle Jurassic (Bathonian) near Oxford, England: from the theropod Megalosaurus or the sauropod Cetiosaurus?


P. M. GALTON a1c1 and F. KNOLL a2a3c2
a1 College of Naturopathic Medicine, University of Bridgeport, Bridgeport, CT 06601, USA
a2 Abteilung Paläontologie, Staatliches Museum für Naturkunde, 70191 Stuttgart, Germany
a3 CNRS UMR 5143, Muséum national d'Histoire naturelle, 75231 Paris cedex 05, France

Article author query
galton pm   [Google Scholar] 
knoll f   [Google Scholar] 
 

Abstract

A dinosaur braincase from the Middle Jurassic (Bathonian) of Oxfordshire (England) is described. The specimen, which has historical significance, has been erratically attributed to either a sauropod or a theropod on the basis of vague phenetic resemblances. It is here re-interpreted in the light of recent cladistic analyses of dinosaurs, allowing the first proper character-based discussion of its affinities. It resembles those of ornithischian and prosauropod dinosaurs in the absence of a prominent, caudolaterally directed bony sheet from either the crista tuberalis (as in all theropods) or the crista prootica (as in all sauropods except juveniles of the eusauropod Shunosaurus). This braincase shows two synapomorphic characters of the Eusauropoda: the region of the cranium is rostrocaudally shortened and the long axis of the supratemporal fenestra is transversely oriented. For these characters, ornithischians, theropods, and prosauropods retain the plesiomorphic condition. It is concluded that the specimen is an important exemplar of a Middle Jurassic sauropod braincase and it is suggested that it could be from the eusauropod Cetiosaurus.

(Published Online September 18 2006)
(Received February 7 2005)
(Revised March 13 2006)
(Accepted March 28 2006)


Key Words: systematics; phylogeny; sauropod; Jurassic; England.

Correspondence:
c1 Author for correspondence: knoll.smns@naturkundemuseum-bw.de, knoll@mnhn.fr
c2 315 Southern Hills Drive, Rio Vista, CA 94571, USA.


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