Staurikosaurus pricei Colbert 1970

Staurikosaurus pricei Colbert, 1970

AGE: Late Carnian–early Norian, Late Triassic Alemoa local fauna (Langer, 2005a).

OCCURRENCE: Alemoa Member, Santa Maria Formation, Rio Grande do Sul state, Brazil.

HOLOTYPE: MCZ 1669, incomplete skeleton including partial mandibular rami, almost complete vertebral column including six cervical vertebrae, most of the trunk and caudal series, the complete sacrum, two fragments of the scapulocoracoid, a bone fragment of uncertain affinities attributed to the humerus (Galton, 2000), almost complete ilia, pubes, ischia, femora, and the left tibia and fibula.

REMARKS: Staurikosaurus was named by Colbert (1970) for a unique specimen from the Triassic Santa Maria sequence in southern Brazil. The age and provenance makes Staurikosaurus a very important specimen for answering questions about early dinosaur diversification, relationships, and early evolution. The partially articulated skeleton preserves much of the axial column and pectoral girdle but lacks forelimbs, most of the skull, and the ever-important pes. Unfortunately, the surfaces of the bones are poorly preserved, and the identification of some of the more incomplete elements found with the specimen continue to be debated (see Galton, 2000).

Researchers have generally agreed that Staurikosaurus is a dinosaur, but placement within Dinosauria remains controversial. Staurikosaurus was found as the sister taxon of Herrerasaurus in phylogenetic analyses (Novas, 1992; Sereno, 1999; Rauhut, 2003; Langer, 2004; Langer and Benton, 2006) or suggested as a more basal dinosaurian taxon (Galton, 1977; Brinkman and Sues, 1987). Out of the possible autapomorphies of Staurikosaurus listed by Bittencourt and Kellner (2005), none seems to be restricted to the taxon. I agree with Rauhut (2003) that a postacetabular process of the ilium abbreviated and straight posteriorly is an autapomorphy of the taxon.

KEY REFERENCES: Colbert, 1970; Galton, 1977, 2000; Bittencourt and Kellner, 2005.