Field of Science

Antarctosuchus polyodon, a new Temnospondyl from the Middle Triassic of Antarctica and Evidence for the Provincialization of the Temnospondyl Assemblages of Gondwana

I've always been interested in the Triassic rocks of Antarctica since as a work-study student at the Museum of Northern Arizona in the 1990s, I was tasked with returning a loan back to the American Museum of Natural History. Turns out it was Edwin Colbert's collection of material from Antarctica.  I was spellbound handling and packing away leaves of Glossopteris and specimens of Thrinaxodon and Dicynodon. These were specimens I had read about when I was younger that helped nail down the theory of plate tectonics, and here I was handling them and packing them for shipment (I hope they made it OK). In graduate school in the late 1990s we were tasked with writing a mock NSF proposal.  Mine dealt with collecting fossils in the Transantarctic Mountains and I'm happy to say it was the only one 'funded' by the professor, but of course I did not really get to go. As a result I'm always envious when  I read about Antarctic work.

This is a paper in the new issue of the Journal of Vertebrate Paleontology describing a new temnospondyl from the Middle Triassic of Antarctica.  This new taxon, Antarctosuchus polyodon, is based on a well preserved skull and a reconstruction is provided below courtesy of Christian Sidor.

This new taxon and its phylogenetic relationships suggests that the Gonwanan temnospondyl faunal assemblages were more provincial than the synapsid assemblages.

Sidor, C. A., Steyer, J. S., and W. R. Hammer. 2014. A new capitosaurid temnospondyl from the Middle Triassic Upper Fremouw Formation of Antarctica. Journal of Vertebrate Paleontology 34(3):539-548. DOI:10.1080/02724634.2013.808205

Abstract - We describe a new capitosauroid temnospondyl, Antarctosuchus polyodon, 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 Antarctosuchus 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 Antarctosuchus within a clade of derived Triassic stereospondyls as the sister taxon to Paracyclotosaurus crookshanki from the Triassic Denwai Formation of India. To date, the upper Fremouw Formation has yielded two endemic temnospondyl species (viz., Kryostega collinsoni and Antarctosuchus polyodon), although indeterminate remains referred to benthosuchids and a cranial fragment assigned to Parotosuchus sp. have also been noted. In contrast to the broadly distributed therapsid taxa recognized from the Middle Triassic of Antarctica (e.g., Cynognathus, Diademodon), the temnospondyl fauna suggests more limited interchange with other coeval southern Pangean basins (e.g., Karoo, Luangwa, Ruhuhu, Waterberg).

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