Basking Shark (Lamniformes: Cetorhinidae) from the Lower Oligocene of the Caucasus

Abstract

Based on an almost complete impression from the base of the Pshekha Horizon (layer 2, Planorbella Beds, zone NP 21) of the North Caucasus (lower early Oligocene), we describe the basking shark Caucasochasma zherikhini gen. et sp. nov., differing from other members of family Cetorhinidae by higher number of vertebrae, weakly developed lower lobe of caudal fin, and details of the structure of gill rakers. Based on the structure of the body, it is not excluded that the described taxon was associated with the bottom to a greater degree than other species of the family (Keasius parvus and C. maximus), for which the structure of the body is known. The accumulations of plankton at the bottom could be a possible food resource for Caucasochasma.