Dwarf Stegolophodon from the Miocene of Japan: Passengers on sinking boats

Japanese stegolophodons represent the oldest geological record of insular dwarfism in elephantoids. The Japanese stegolophodons possessed a large body size over the interval from ca. 18 to 17 Ma, but reduced in size to dwarf forms from ca. 17 to 16 Ma. The dwarfing process of the Japanese stegolophodons coincided with subsidence of the proto-Japanese Islands associated with the opening of the Japan Sea.