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1 May 2011 A New Basal Sauropodomorph Dinosaur from the Early Jurassic of South Africa
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A new basal sauropodornorph dinosaur, Arcusaurus pereirabdalorum, sp. nov., is named and described on the basis of a partial, disarticulated but associated skull and dispersed cranial and postcranial elements from at least two individuals. Arcusaurus is part of a distinctive local fauna from the upper Elliot Formation (Lower Jurassic) in the Senekal District, Free State, South Africa. It can be diagnosed by various details of the premaxilla, nasal, and dentary in the skull and the shape of the distal caudal vertebrae. The taxon displays an unusual mix of characteristics. It lacks several synapomorphies of Plateosauria (Phteosaurus Massospondylus and all descendants of their most recent common ancestor) but does display other derived characteristics that are otherwise known only from less inclusive clades within Plateosauria. In a cladistic analysis a position outside Plateosauria as the sister group of the clade of Efraasia more-derived sauropodomorphs is supported; however, this position was not found to be a significantly better explanation of the data as a relatively derived position within Plateosauria. If the basal position for Arcusaurus is accepted, then a divergence from other sauropodomorphs in the middle Norian and a ghost lineage up to 35 Ma is implied. No other non-plateosaurian sauropodomorphs are known from the Jurassic, making Arcusaurus a potentially relictual taxon in the Early Jurassic.

© 2011 by the Society of Vertebrate Paleontology
Adam M. Yates, Matthew F. Bonnan, and Johann Neveling "A New Basal Sauropodomorph Dinosaur from the Early Jurassic of South Africa," Journal of Vertebrate Paleontology 31(3), 610-625, (1 May 2011).
Received: 23 August 2010; Accepted: 1 January 2011; Published: 1 May 2011

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