Beaver jaw

Beaver jaw

NMMNH P-19248

Extinct beaver

Rodent

West of Rio Rancho, Sandoval County

Middle Miocene, 14 million years ago

Lower jaw with 5 teeth

Extinct beavers of the genus Monosaulax are common members of the Miocene fauna of New Mexico, especially in certain fossil sites in the Rio Puerco Valley west of Rio Rancho. Although these Miocene beavers probably were not semi-aquatic rodents with a broad paddle-like tail as in the living beaver (scientific name Castor canadensis), their fossils are often found in fine-grained sediments deposited in quiet water, indicating they lived near permanent freshwater sources such as ponds or streams.