Frilled Sharks (Hexanchiformes, Chlamydoselachidae): New Data on Their Diversity and Distribution

Findings of frilled sharks (both fossil and modern) are very rare, primarily due to their deep-sea lifestyle. A tooth of frilled shark Chlamydoselachus kamchaticus sp. nov. has been found in the Upper Eocene sediments of the Peresheek Mountain Formation on Karaginsky Island (Bering Sea, off northeastern Kamchatka). The large size of the tooth suggests a fish size close to the maximum for the genus, more than twice the size of modern Chlamydoselachus. This find is northernmost for fossil frilled sharks and located 20° north of the modern northern limit of the genus’ distribution in the Pacific Ocean. This may indicate a warmer climate in the Late Eocene than the current climate conditions in the region of Eastern Kamchatka.