Rodentia
Giant Pleistocene Rodents
Rodents are mammals characterized primarily by a single pair of continuously growing incisors in both the upper and lower jaws. These incisors are large and chisel-shaped, well adapted for gnawing through tough materials. Rodents lack canine teeth and typically have a distinct gap called a diastema between their incisors and their cheek teeth. Rodents include all of today's mice, rats, gerbils, guinea pigs and porcupines, but during the Pleistocene epoch some North American rodents reached massive sizes. In particular the Giant Beaver Castoroides may have been the largest rodent to live in North America.
Giant beaver
Castoroides ohioensis
Temporal Range: 1.9 million years ago to approximately 11,000 years ago
Geographic Range: Found across North America from the Yukon to Florida
Species: C. ohioensis, C. dilophidus
Diet: Herbivorous, grasses, aquatic plants
Castoroides, commonly known as the giant beaver, was one of the largest rodents ever to live in North America. This massive mammal inhabited lakes, marshes, and wetland habitats. Its fossils have been discovered across much of North America, with one species most often found in the Midwest (C. ohioensis) and another species found in the southeastern US (C. dilophidus)
Unlike modern beavers, Castoroides was enormous, reaching lengths of about 7 feet and weighing about as much as a small bear. Its body was heavily built, with large hind feet that likely aided with swimming. Their tails may have been longer and less paddle-shaped than those of living beavers. One of Castoroides' most notable features was the size of its incisors, which could grow to be over 6 inches long. These teeth had a textured enamel surface not seen in the chisel-like incisors of modern beavers. Evidence suggests that Castoroides fed primarily on aquatic vegetation rather than cutting down large trees.
(BELOW) A labeled diagram of the skeletal anatomy of the giant beaver Castoroides. Drawing is based on a mounted skeleton on display at the Joseph Moore Museum in Richmond, Indiana. Note the extremely large size of the incisors.
(BELOW) A partial cranium of Castoroides displayed alongside the cranium of an extant beaver. These huge rodents could easily weigh 20 times more than their smaller relatives.
Media Gallery
Suggested References: Rodentia
Harington, C.R. (2007). "Giant Beaver, Castoroides ohioensis, remains in Canada and an overlooked report from Ontario". Canadian Field-Naturalist. 121 (3): 330–333.
Korth, William W (1994). “The Tertiary record of rodents in North America”. Springer. p. 145.
Parmalee P. W.; Graham R. W. (2002). "Additional records of the giant beaver, Castoroides, from the Mid-South: Alabama, Tennessee, and South Carolina". Smithsonian Contributions to Paleobiology. 93: 65–71.
Plint, Tessa; Longstaffe, Fred J.; Zazula, Grant (2019). "Giant beaver palaeoecology inferred from stable isotopes". Scientific Reports. 9 (7179): 1–12.
Swinehart, Anthony L., and Richards, Ronald L. (2001) "Palaeoecology of a Northeast Indiana Wetland Harboring Remains of the Pleistocene Giant Beaver (Castoroides Ohioensis)." Indiana Academy of Science.