title: A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina.
abstract: Herrerasauridae comprises a basal clade of dinosaurs best known from the Upper Triassic of Argentina and Brazil, which have yielded remains of Herrerasaurus ischigualastensis and Staurikosaurus pricei, respectively. Systematic opinion regarding the position of Herrerasauridae at the base of Dinosauria has varied. Here we describe a new herrerasaurid, Sanjuansaurus gordilloi gen. n., sp. n., based on a partial skeleton from Carnian-age strata of the the Upper Triassic Ischigualasto Formation of northwestern Argentina. The new taxon is diagnosed by numerous features, including long, band-shaped and posterolaterally oriented transverse process on the posterior cervical vertebrae; neural spines of the sixth to eighth dorsal vertebrae, at least, bearing acute anterior and posterior processes; scapula and coracoid with everted lateral margins of the glenoid; and short pubis (63% of the femoral length). Phylogenetic analysis placed Sanjuansaurus within a monophyletic Herrerasauridae, at the base of Theropoda and including Herrerasaurus and Staurikosaurus. The presence of Sanjuansaurus at the base of the Ischigualasto Formation, along with other dinosaurs such as Herrerasaurus, Eoraptor, Panphagia, and Chromogisaurus suggests that saurischian dinosaurs in southwestern Pangea were already widely diversified by the late Carnian rather than increasing in diversity across the Carnian-Norian boundary.
authors: Museo de Ciencias Naturales, San Juan 5400, Argentina.
authors: Oscar A
authors: OA
authors: Alcober
authors: Ricardo N
authors: RN
authors: Martinez
references: Science. 1999 Jun 25;284(5423):2137-47
references: 10381873
references: Science. 1993 May 7;260(5109):769-70
references: 17746108
references: An Acad Bras Cienc. 2000 Dec;72(4):509-38
references: 11151018
references: Biol Rev Camb Philos Soc. 2010 Feb;85(1):55-110
references: 19895605
references: PLoS One. 2009;4(2):e4397
references: 19209223
references: Science. 2009 Dec 11;326(5959):1530-3
references: 20007898
references: Science. 1992 Nov 13;258(5085):1137-40
references: 17789086
references: Science. 1993 May 7;260(5109):794-7
references: 17746113
references: Science. 2007 Jul 20;317(5836):358-61
references: 17641198