An Oldest Record of the Shark Cosmopolitodus planus (Lamnidae) from the Lower Miocene of the Sakhalin, Russia

Abstract

An isolate tooth of a rare extinct hook-toothed mako Cosmopolitodus planus (Agassiz, 1856), discovered in the Lower Miocene deposits of the Chekhov Formation of Sakhalin Island is described. This extinct species was distributed exceptionally in the Pacific basin, and is known mainly from the deposits of the Middle and Upper Miocene. Thus, the described tooth is, probably, the oldest record of this species. The geographic and stratigraphic distribution of this species, as well as the validity of the genus Cosmopolitodus Glickman, 1964, are discussed.