Feb. 22 (UPI) — Newly recovered giant rodent fossils suggest paleontogists must rethink the organization of Dinomyidae, the family of giant South American rodents.
The new fossils belong to the now-extinct giant rodent species Isostylomys laurdillardi. The fossils included an adult and a juvenile specimen. Analysis of the fossils revealed surprisingly similar teeth structures.
Previously, paleontologists were under the assumption juvenile giant rodent teeth would be structurally immature and appear different in their adult form. Thus, researchers assumed some smaller giant rodent specimens represented different species.
The two new fossils are two of the most complete yet discovered. Most ancient giant rodent fossils have consisted of isolated teeth, as well as the odd skull or jaw fragment.
A comparison of the new fossils with capybara specimens, the largest living rodent species, suggests the current Dinomyidae family tree is confused.
“Comparing them we conclude that from very young the giant rodents already were very similar to the adults which allows us to deduce that the great majority of the hypotheses before posed were wrong,” Andres Rinderknecht, a paleontologist at the National Museum of Natural History in Montevideo, said in a news release. “The juvenile and the adult analyzed here represent some of the largest rodents known to science with some of these animals weighing almost a ton.”
The findings — published in the Journal of Systematic Palaeontology — are likely to force scientists to reconsider the organization of species and subfamilies within the dominids.
“The dental ontogeny of large-sized rodents casts doubt on the validity of the subfamily Gyriabrinae, which may be composed of juveniles of different taxa within other subfamilies of Dinomyidae,” researchers concluded.
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