Enhydra and Enhydriodon from the Pacific Coast of North America

Two lineages of the "crab-eating" otter Erihydriodon, from the Old World Miocene and Pliocene, are suggested by the fossil record. One appears to lead to the late Pliocene Enhydriodon sivalensis from Villafranchian-equivalent beds in India and can be characterized by the presence of a parastyle on P⁴ and by the location of the protocone of this tooth, which is located as far lingually as is the hypocone. In the other lineage no parastyle is developed on P⁴, the anteroposterior length of the carnassial blade is progressively reduced while the transverse width is increased, and the protocone of P⁴ remains in its primitive position anterolateral to the hypocone. The second lineage, insofar as it is known, seems to lead toward the living sea otter Enhydra, particularly so because of the evolutionary direction shown by two species of Enhydriodon from the late Miocene and late Pliocene of California.