Fossil detection of two new rodents

Scientists working at the School of Medicine, Case Western Reserve University, USA and Autónoma Tomás Frías University, Bolivia, discovered two new rodent fossils in the arid plateau in southern Bolivia.

Fossil Quebrada Hondomys potosiensis .

The larger fossil in the discovery is named Mesoprocta hypsodus , which has a characteristic body that looks like a hamster with four long legs like walking on stilts, according to Darin Croft, professor of surgery at the university. Case Western Reserve, USA. The smaller fossil called Quebradahondomys potosiensis , looks like a small thorny rat.

The findings have been published in Mammalian Evolution magazine, where the two fossils represent two completely new rodents.

"These two new species are quite rare, " said Professor Darin Croft. Croft's team has been working for the past five years and has identified only one fragment of jaw bone from each fossil animal.

Professor Darin Croft had to come to this remote area, about 12,000 feet from sea level, as well as areas where previous research was mainly in the mountains of the North and Central Chile, for about 14 years. . This excavation site is one of the highest areas in the Western Hemisphere.

Croft and his colleagues discovered and documented more than 24 new mammal species, ranging from small marsupials with mice to giant hooves with hooves , and herbivores are about the size of sheep during that time.

Previous research used radiometer and magnetometer techniques to determine the age of fossils (at Quebrada Honda, Bolivia excavation site) between 12.5 and 13 million years ago.

Although the details of the two newly discovered fossils are limited, their teeth provide the necessary properties to determine their species origin and identity.

The Mesoprocta hypsodus fossil has a relative of the current two rodents, agoutis and acouchis , which live in large areas distributed from Costa Rica to Brazil. These rodents have such outstanding features as: tall, complex teeth, known for their cute faces, long legs and agile movements.

Based on the size of the teeth and jaw, Croft estimates extinct rodents about 45.72 cm to 50.8 cm long (with a foot about 20.32 cm high) and heavy from 3.6 to 4.5 kg.

Croft said that although this rodent can eat fruits and nuts, just like modern relatives, they have strong teeth, proving they have ventured to find food in large areas. . However, their living environment no longer exists in Quebrada Honda, Bolivia.

The Quebradahondomys potosiensis fossil is a relatively small rat-like species of rat, which is a relative of rats and squirrels that live on trees, with cape and tail spines, making it easy to move. to help them escape the beast. Currently, the rat is found throughout Central America and most of South America.

Molars shaped like " 3 " or " E ", are typical of a specific subgroup of thorny mice and show that these extinct rodents eat the leaves. Researchers believe these rodents live on trees and feed on the ground.

In addition to the two new species above, Croft's team also found some fossils belonging to the genus Acarechimys.

These remaining fossils show that they are hamster-sized animals, live in burrows, bushes, eat leaves and seeds.

Fossils of the genus Acarechimys, were found from Colombia to the southern tip of Argentina, but rigorous analysis is needed to divide specific species. The researchers continued their search in the hope of identifying new species from the fossils found.

The most common fossil in this excavation site is related to Len squirrel, all of which belong to the genus Prolagostomus . They were found in such large numbers that the researchers believe that this highly social animal, like some of their current relatives, lives in crowded communities like prairie dogs. nowadays.

Recent analyzes of fossils are found here and in other locations to identify specific species. In addition, the study of change in their modern relatives is also useful support.

Finally, investigators found fossils of the Guiomys UNICA , a relative of the guinea pig. This Guiomys UNICA is estimated to be the size of a large rabbit, but as balanced as a cat, previously available only in Argentina's Patagonia region, a place more than 1,000 miles away.

This is a herbivore and leaf, living regularly in both open habitats and in dense areas, the researchers said.

Researchers are also continuing to analyze other fossils, which were found at this site and at other excavation sites in Bolivia. They plan to return to the area next year to continue searching for fossils and sketch a clearer picture of the past.

" We got closer to pulling the whole animal system together, " Croft said. " I absolutely hope we will get some new results in the next few years. "

The research is funded by the National Geographic Association and the National Science Foundation.