''Dipoides'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of beaver-grouped

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

s. ''Dipoides'' were approximately three to four times larger than modern Canadian beavers - ranging from 90 - 120KG. 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 Ellesmere Island (; ) is Canada's northernmost and List of Canadian islands by area, third largest island, and the List of islands by area, tenth largest in the world. It comprises an area of , slightly smaller than Great Britain, and the total ...

, 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. 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 The Neogene ( ,) is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period million years ago. It is the second period of th ...

period. Natalia Rybczynski, of the

Canadian Museum of Nature The Canadian Museum of Nature (; CMN) is a national museums of Canada, national natural history museum based in Canada's National Capital Region (Canada), National Capital Region. The museum's exhibitions and public programs are housed in the Vi ...

, analyzed the teeth, and wood chips, of modern beavers, and ''Dipoides''. 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.

References

External links

Dipoides Jaeger 1835
on: Encyclopedia of Life, National Museum of Natural History, Smithsonian Prehistoric beavers Prehistoric rodent genera Ringold Formation Miocene Fauna Fossil taxa described in 1835 {{paleo-rodent-stub