Castoroides

Castoroides (from Latin castor (beaver) and -oides (like)), or the giant beaver, is an extinct genus of enormous, bear-sized beavers that lived in North America during the Pleistocene. Two species are currently recognized, C. dilophidus in the Southeastern United States and C. ohioensis in most of North America. C. leiseyorum was previously described from the Irvingtonian age but is now regarded as an invalid name. All specimens previously described as C. leiseyorum are considered to belong to C. dilophidus.

==Description== left|thumb|221x221px|C. ohioensis skull cast (right), compared to a North American beaver skull (left). The former is a cast of a specimen from [[Shelby County, Iowa. At the AMNH.]] Castoroides species were much larger than modern beavers. Their average length was approximately , and they could grow as large as . The weight of the giant beaver could vary from to . This makes it the largest known rodent in North America during the Pleistocene and the largest known beaver. Recent analyses suggest that they weighed less, closer to , but this is disputable.