(ORDO NEWS) — Scientists have described the fossils of the teeth and talus of an ancient rodent found in Montana. The remains belong to a waterfowl beaver, which was named Microtheriomys articulaquaticus.
The species lived 30 million years ago, 7 million years earlier than the Eurasian swimming beaver, which was considered the oldest before this discovery.
Scientists from Ohio State University have described the teeth and ankle bones of North America’s oldest waterfowl rodent, the beaver, called Microtheriomys articulaquaticus.
To classify the animal, the scientists compared the morphology of its talus to those of 343 other rodents. M. articulaquaticus is 30 million years old.
Previously, the species, the remains of which were found in France, was considered the oldest waterfowl, presumably living 23 million years ago.
“Rodents are incredibly diverse today. There are gliding rodents such as flying squirrels, jumping rodents such as kangaroo rats, aquatic species such as muskrats and beavers, and burrowing animals such as ground squirrels.
When this diversity arose is an important question, says study leader Jonathan Kalede. “Rodents are the most diverse group of mammals on Earth, with 4 out of 10 mammal species being a rodent.”
A M. articulaquaticus fossil was found in western Montana. The structure of the animal’s teeth immediately led scientists to the idea that they were looking at a beaver. However, the subsequent study of the talus revealed much more about the life of this species.
The talus in beavers is where the lower leg meets the top of the foot, just like in humans. Analysis of the data showed that waterfowl probably evolved as a result of using existing anatomy for a new way of life.
Initially, beavers were adapted to burrowing, and later switched to a semi-aquatic lifestyle. Movement in the depths of the earth and in water requires similar adaptations of the skeleton and muscles.
Fish and frog fossils found alongside M. articulaquaticus support the fact that it lived in an aquatic environment. M. articulaquaticus did not yet have a flat tail and probably fed on herbaceous plants rather than trees.
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