A new gastropod mollusc, Antarctissitys austrodema gen. et sp. nov., from the upper Maastrichtian of Antarctica and its evolutionary significance

The Maastrichtian López de Bertodano Formation of Seymour Island, Antarctic Peninsula, hosts the most diverse assemblage of Late Cretaceous molluscs from the continent. Described here is a new genus and species of gastropod, Antarctissitys austrodema gen. et sp. nov., from the upper units of the formation, which are inferred to represent a mid-shelf clastic environment. Antarctissitys austrodema is assignable to the Perissityidae (Muricoidea) and is the first confirmed record of this family in the Southern Hemisphere, indicating a much more widespread Cretaceous geographic distribution. Fusus dusenianus Wilckens from the Upper Cretaceous of Patagonia and Perissitys? sp. from the Maastrichtian of New Zealand may also belong in Perissityidae, but preservational deficiencies prevent any firm assessment. The affinities of Antarctissitys gen. nov. lie with a diverse suite of perissityid taxa in the Upper Cretaceous of North America, belonging predominantly to Perissitys.