Braincase de dinosaure de l'Angleterre

Posté par Markvantomme il y a 18 ans

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

P.M.GALTON and F. KNOLL

Geological Magazine, in press , 2006

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.

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