Coniacian ammonites from James Ross Island, Antarctica

The Cenomanian–Santonian biostratigraphy of the James Ross Basin, north-eastern Antarctic Peninsula is in need of comprehensive revision. This is being achieved by the systematic re-investigation of a series of key reference sections on the north-west coast of James Ross Island, with the first of these being located in the vicinity of Brandy Bay. A new suite of 10 ammonite taxa from the uppermost Whisky Bay and Hidden Lake Formations at this locality has overwhelming Coniacian age affinities. It comprises representatives from the Tetragonitidae and Gaudryceratidae, together with the stratigraphically earliest representative of the Kossmaticeratidae and the three earliest Pachydiscidae species from the James Ross Basin. Some fragmentary specimens are assigned to the Collignoniceratidae, and various heteromorphs to the Nostoceratidae, Diplomoceratidae and Baculitidae. The one new taxon described herein is Gaudryceras (Gaudryceras) strictum sp. nov. This ammonite fauna represents an important precursor to the much more prolific assemblages that occur in the overlying Santa Marta and López de Bertodano formations (latest Coniacian–Maastrichtian). It shows some affinities to the Madagascan Coniacian ammonite fauna, and offers an opportunity for strengthening Late Cretaceous biostratigraphic correlations between the northern and southern hemispheres.