A new capitosauroid temnospondyl from the Middle Triassic upper Fremouw Formation of Antarctica

ABSTRACTWe describe a new capitosauroid temnospondyl, <i>Antarctosuchus polyodon</i>, gen. et sp. nov., on the basis of a large and relatively complete skull from the upper Fremouw Formation of Antarctica. The new species is characterized by its possession of numerous, extremely small maxillary, palatine, and ectopterygoid teeth, a dental pattern that suggests specialization on small prey items, possibly invertebrates. The taxon is also characterized by a parachoanal tooth row that extends far posterior to the choana and occipital condyles set close to the midline. A combination of features, including a flat skull and low occiput together with well-developed sensory canals, suggests an aquatic lifestyle. We address the phylogenetic relationships of <i>Antarctosuchus</i> by adding it to a recent cladistic analysis of Capitosauria. The revised data set includes 27 taxa and 53 characters. The results of this analysis place <i>Antarctosuchus</i> within a clade of derived Triassic stereospondyls as the sister taxon to <i>Paracyclotosaurus crookshanki</i> from the Triassic Denwai Formation of India. To date, the upper Fremouw Formation has yielded two endemic temnospondyl species (viz., <i>Kryostega collinsoni</i> and <i>Antarctosuchus polyodon</i>), although indeterminate remains referred to benthosuchids and a cranial fragment assigned to <i>Parotosuchus</i> sp. have also been noted. In contrast to the broadly distributed therapsid taxa recognized from the Middle Triassic of Antarctica (e.g., <i>Cynognathus</i>, <i>Diademodon</i>), the temnospondyl fauna suggests more limited interchange with other coeval southern Pangean basins (e.g., Karoo, Luangwa, Ruhuhu, Waterberg).SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at http://www.tandfonline.com/UJVP.