Dipoides

Dipoides is an extinct genus of beaver-grouped rodents.[1][2]

Dipoides Temporal range: Late Miocene to Late Pliocene
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Castoridae
Tribe:	†Castoroidini
Genus:	†Dipoides Schlosser, 1902

Dipoides were about two thirds the size of modern Canadian beavers.[2] Where modern beavers have square chisel shaped teeth, Dipoides teeth were rounded. However an excavation of a site that was once a marsh, in Ellesmere Island, showed signs that they dined on bark and young trees, like modern beavers. The excavation seemed to show that, like modern beavers, Dipoides dammed streams.[3] Other research suggests that the building of dams by Dipoides started as a side effect to the consumption of wood and bark, and was a specialization that evolved for cold weather survival due to the earth's cooling during the late Neogene period.[4]

Natalia Rybczynski, of the Canadian Museum of Nature, analyzed the teeth, and wood chips, of modern beavers, and Dipoides.[2] She concluded that they all used just one of their teeth at a time, when cutting down trees. She concluded that modern beavers square teeth required half as many bites as Dipoides less evolved round teeth.

Rybczynski argues that eating bark and building dams are unlikely to have evolved twice, so modern beavers and Dipoides shared a wood eating common ancestor, 24 million years ago.[2][3]