Glacialisaurus hammeri, Smith & Pol, 2007

Smith, Nathan D. & Pol, Diego, 2007, Anatomy of a basal sauropodomorph dinosaur from the Early Jurassic Hanson Formation of Antarctica, Acta Palaeontologica Polonica 52 (4), pp. 657-674 : 659

Glacialisaurus hammeri sp. nov.

Figs. 2–6 , Table 1.

Holotype: FMNH PR 1823, a partial right astragalus, medial and lateral distal tarsals, and partial right metatarsus preserved in articulation with each other.

Referred material: FMNH PR 1822, a distal left femur.

Type locality: Mt. Kirkpatrick, Beardmore Glacier region, Central Transantarctic Mountains, Antarctica.

Type horizon: Approximately 4,100 meters, in the tuffaceous siltstones and mudstones of the lower part of the Hanson Formation, which is Early Jurassic in age ( Elliot 1996).

Derivation of the name: In honor of Dr. William R. Hammer (Augustana College, Rock Island, USA), for his contributions to vertebrate paleontology and Antarctic research.

Diagnosis.—A robust non−eusauropod sauropodomorph dinosaur that can be distinguished from other sauropodomorphs by the presence of the following autapomorphies: (1) a robust medial epicondylar ridge on the distal femur (convergently present, though more gracile, in many basal theropod dinosaurs); (2) a robust adductor ridge extending from the proximal end of the femoral medial condyle; (3) a second metatarsal with an anterior border that is weakly convex in proximal aspect; (4) a hypertrophied lateral plantar flange on the proximal end of metatarsal II (present, but less developed in many basal sauropodomorphs, e.g., Saturnalia , Plateosaurus ); (5) a second metatarsal that is gently twisted medially about its long axis at the distal end of its shaft; and (6) a second metatarsal with a medial distal condyle that is more robust and well−developed than the lateral distal condyle.

Figures

Fig. 2. Sauropodomorph dinosaur Glacialisaurus hammeri gen. et sp. nov. from the Early Jurassic Hanson Formation at Mt. Kirkpatrick, Beardmore Glacier region, Antarcticac. Distal left femur (FMNH PR1822) in anterior (A), lateral (B), posterior (C), and medial (D) views.

Fig. 3. Sauropodomorph dinosaur Glacialisaurus hammeri gen. et sp. nov. from the Early Jurassic Hanson Formation at Mt. Kirkpatrick, Beardmore Glacier region, Antarcticac.Distal left femur (FMNH PR1822) in distal view.

Fig. 4. Sauropodomorph dinosaur Glacialisaurus hammeri gen. et sp. nov. from the Early Jurassic Hanson Formation at Mt. Kirkpatrick, Beardmore Glacier region, Antarcticac. Right astragalus (FMNH PR1823) in dorsal (A), and posterior (B) views. Right distal tarsals and metatarsus have been digitally removed in A.

Fig. 5. Sauropodomorph dinosaur Glacialisaurus hammeri gen. et sp. nov. from the Early Jurassic Hanson Formation at Mt. Kirkpatrick, Beardmore Glacier region, Antarcticac. Right pes (FMNH PR1823) in anterior (A), medial (B), and posterior (C) views. Astragalus and distal tarsals have been digitally removed in B.

Fig. 6. Sauropodomorph dinosaur Glacialisaurus hammeri gen. et sp. nov. from the Early Jurassic Hanson Formation at Mt. Kirkpatrick, Beardmore Glacier region, Antarcticac. Right metatarsal II (FMNH PR1823) in distal view. Anterior is toward the top of the page. Note the medial twisting of the distal articular end, and the more robust development of the medial condyle.