Cretaceous wood-boring bivalves from Western Antarctica with a review of the Mesozoic Pholadidae
Antarctic wood-boring bivalves are described from the Kotick Point Formation, Gustav Group (Early Cretaceous) and the Marambio Group (Late Cretaceous) of the James Ross Island group, and from the Early Cretaceous part of the Fossil Bluff Formation of eastern Alexander Island. They are identified as the pholadid genera Opertochasma, Teredina, Turnus, and Xylophagella. All but Turnus are recorded here from the Antarctic for the first time. The following new species are described: Opertochasma psyche, Teredina jeffersoni, Turnus kotickensis, and Xylophagella truncata. Particularly well-preserved accessory plates occur in Opertochasma and Teredina. The borings containing the bivalves are referred to the ichnogenus Teredolites. Preparation techniques used include serial sectioning and casting in silicone rubbers. The stratigraphical and geographical distributions of the genera and their palaeoecology are briefly discussed. First appearances of world-wide Mesozoic pholadid genera are reviewed and an attempt is made to construct a phylogeny for the early history of the group. Teredolites is known from Pliensbachian time, but the earliest body fossil, 'Teredo' australis, is Middle Jurassic in age and of doubtful generic affinity. Opertochasma and Turnus appeared in the Late Jurassic and Xylophagella in the Early Cretaceous. During the Late Cretaceous the group began to flourish and diversify.