Name: »San Juan lizard«
Length: 1,5 m
Height: 0,7 m
Weight: 13 kg
Time: Triassic (231 MYA)
Location: South America (Argentina)
Sanjuansaurus ((Greek for “San Juan lizard”); pronounced san-wahn-SORE-us). I a genus of herrerasaurid dinosaur from the Late Triassic-age Ischigualasto Formation of northwestern Argentina. It is known from and based on an associated and partially-articulated partial skeleton (PVSJ 605) consisting of a jaw fragment, most of the vertebral column from the axis to the anterior tail, the shoulder blades, an ulna, part of the pelvis, most of the long bones of the legs, and a few other bones. PVSJ 605 was found in the Cancha de Bocas Member near the base of the Ischigualasto Formation, in Ischigualasto Provincial Park in San Juan. This horizon dates to approximately 231.4 Ma, during the late Carnian Stage of the Late Triassic.
Sanjuansaurus was named and described in 2010 by Oscar Alcober and Ricardo Martinez. The type species is S. gordilloi after Raul Gordillo, the head fossil preparator and artist of the San Juan Museum. Sanjuansaurus was a contemporary of other early dinosaurs including Chromogisaurus, Eoraptor, Herrerasaurus, and Panphagia. It was comparable in size to a medium-sized Herrerasaurus, with a thigh bone length of 395 millimetres (15.6 in). Alcober and Martinez performed a phylogenetic analysis and found Sanjuansaurus to be a herrerasaurid.
Barring a better hypothesis, paleontologists believe that the first dinosaurs, the early theropods, evolved in South America about 230 million years ago. Discovered recently in Argentina, Sanjuansaurus seems to have been closely related to the better-known basal theropods Herrerasaurus and Eoraptor.
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.
Species: S. gordilloi Alcober and Martinez, 2010