A MIDDLE EOCENE BASKING SHARK (LAMNIFORMES, CETORHINIDAE) FROM ANTARCTICA

A proximal fragment of a gill raker identified as belonging to a shark of the genus Cetorhinus was collected from middle Eocene deposits of the La Meseta Formation in the northern part of Seymour Island, Antarc tica. This is the first record of a fossil basking shark from Antarcti ca and one of the earliest records of the genus. The minimum age of Ce torhinidae is middle Eocene. The only living species of the family Cet orhinidae is a very large plankton feeder, Cetorhinus maximus. Basking sharks are unknown in subantarctic or Antarctic waters but occur on b oth South American coasts today. The evolution of filter-feeding verte brates is discussed.