A NEW BASAL SAUROPODOMORPH FROM THE EARLY JURASSIC HANSON FORMATION OF ANTARCTICA

The latest expedition to the Transantarctic mountains, Antarctica (2010-2011), has yielded the remains of two possible new taxa from the early Jurassic Hanson Formation. Earlier expeditions to the Mt. Kirkpatrick region of the Transantarctics have produced a diverse fossil assemblage including Cryolophosaurus ellioti, Glacialisaurus hammeri, an undescribed pterosaur humerus, and a tritylodont postcanine tooth. Here we describe the remains of a partial skeleton of a basal sauropodomorph dinosaur discovered near the same locality on Mt. Kirkpatrick, Antarctica. The material includes the anterior portion of the left ilium, including a proportionally elongate preacetabular process and the dorsal and anterior portions of the acetabulum including the pubic peduncle. It also includes the incomplete shaft and proximal end of the left ischium, including the obturator process, but lacking the anterior extension, the distal end of the left pubis, a nearly complete right pubis, and the last two posterior dorsal vertebrae articulating with the first sacral vertebra.

Based on plesiomorphic and derived characters, especially of the ilium and vertebrae, this material represents a taxon within the family Massospondylidae. Due to the size of the specimen and the lack of fusion between the neural arches and the centra, the specimen appears to be that of a juvenile animal. The material may represent that of a juvenile Glacialisaurus hammeri, a taxon found in close proximity though slightly lower in the section, however further investigation is needed.

Although little is known about the temporal, spatial, and phylogenetic relationships within basal sauropodomorphs, especially within the Antarctic region, several recent discoveries from early Jurassic of South America has helped elucidate some of these issues. The material described herein is important for the understanding of biodiversity and biogeographic implications of Antarctica during the Early Jurassic and will aid in providing new data for the debate on basal sauropodomorph phylogenetics.