North American River Otter - Taxonomy and Evolution

Taxonomy and Evolution

The North American river otter was first described by German naturalist Johann Christian Daniel von Schreber in 1777. The mammal was identified as a species of otter and has a variety of common names, including North American river otter, northern river otter, common otter and, simply, river otter. Other documented common names are American otter, Canada otter, Canadian otter, fish otter, land otter, nearctic river otter, and Prince of Wales otter.

The river otter was first classified in the genus Lutra; Lutra was the early European name. The species name was Lutra canadensis. The species epithet canadensis means "of Canada".

In a new classification, the species is called Lontra canadensis, where the genus Lontra includes all the New World river otters. Molecular biological techniques have been used to determine when the river otter and the giant otter diverged. These analyses suggest they diverged in the Miocene epoch 23.03 to 5.33 million years ago (Mya), which is "much earlier" than indicated in the fossil record. Fossils of a giant river otter dating back 3.5 Mya have been found in the US Midwest, however fossils of the modern river otter did not appear in North America until about 1.9 Mya. The earliest known fossil of Lontra canadensis, found in the US Midwest, is from the Irvingtonian stage (1,800,000 to 300,000 years ago). The oldest fossil record of an Old World river otter comes from the late Pliocene epoch (3.6 to 1.8 Mya). The New World river otters originated from the Old World river otters after a migration across the Bering Land Bridge, which existed off and on between 1.8 million and 10,000 years ago. The otters migrated to North America and southwards again across the Panamanian Land Bridge, which formed 3 Mya.