A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods

Benson, R. B. J. (2010) A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods. Zoological Journal of the Linnean Society, 158 (4). pp. 882-935. ISSN 0024-4082 DOI 10.1111/j.1096-3642.2009.00569.x

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Abstract

Megalosaurus bucklandii (Dinosauria: Theropoda), the oldest named dinosaur taxon, from the Bathonian (Middle Jurassic) of England, is a valid taxon diagnosed by a unique character combination of the lectotype dentary. Abundant referred material is described and several autapomorphies are identified: ventral surfaces of first and third to fifth sacral centra evenly rounded, ventral surface of second sacral centrum bearing longitudinal, angular ridge; dorsally directed flange around midheight on the scapular blade; an array of posterodorsally inclined grooves on the lateral surface of the median iliac ridge; anteroposteriorly thick ischial apron with an almost flat medial surface; and complementary groove and ridge structures on the articular surfaces between metatarsals II and III. A new phylogenetic analysis focuses on basal tetanurans and includes 41 taxa, six of which have never been included in a cladistic analysis, and 213 characters, 29 of which are new. This is the first phylogenetic analysis to focus on basal tetanuran relationships, and it reveals several new results. Megalosauroidea (= Spinosauroidea) includes two clades, basal to the traditional content of Megalosauridae + Spinosauridae. These comprise Xuanhanosaurus, Marshosaurus, Condorraptor + Piatnitzkysaurus and Chuandongocoelurus + Monolophosaurus. Almost all large-bodied Middle Jurassic theropods are megalosauroids, but Poekilopleuron is an allosauroid. Megalosauroids show geographical differentiation among clades, indicating the development of endemic theropod faunas across Pangaea during the Middle Jurassic. Notably, megalosaurids are not known from outside of Europe during this epoch. Megalosauroids are less diverse and abundant during the Late Jurassic, when most theropods are neotetanurans and allosauroids dominate the large-bodied predator niche. This indicates faunal turnover between the Middle and Late Jurassic.

Item Type: Article
Uncontrolled Keywords: 09AREP; IA60,
Subjects: 04 - Palaeobiology
Divisions: 04 - Palaeobiology
Journal or Publication Title: Zoological Journal of the Linnean Society
Volume: 158
Page Range: pp. 882-935
Identification Number: 10.1111/j.1096-3642.2009.00569.x
Depositing User: Sarah Humbert
Date Deposited: 01 Apr 2010 08:43
Last Modified: 23 Jul 2013 09:57
URI: http://eprints.esc.cam.ac.uk/id/eprint/1362

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