Two new rodent fossils were discovered in the arid highlands of southern Bolivia by researchers from Case Western Reserve University School of Medicine and Universidad Autnoma Toms Fras.
The larger of the two rodents, named Mesoprocta hypsodus, probably looked something like a guinea pig on stilts, said Darin Croft, an anatomy professor at Case Western Reserve. The smaller, Quebradahondomys potosiensis, was a spiny rat.
An online article in the Journal of Mammalian Evolution describes the new species, a possible third, and two known species that are new inhabitants to that location.
"The two new species are pretty rare," said Croft. Various teams have been working the Bolivian site, called Quebrada Honda, on and off since the late 1970s. Croft's team has been working there for the past five years and has identified only one fossilized piece of jawbone from each animal.
Croft has been working this remote area, about 12,000 feet above sea level, as well as largely understudied areas in the mountains of northern and central Chile, for 14 years. The research sites are among the highest in the Western Hemisphere.
He and his colleagues have found and documented remains of more than two-dozen new species of mammals, ranging from mouse-sized marsupials to giant armadillos and hoofed, sheep-sized grazers in that time.
Prior research using radiometric and paleomagnetic dating techniques puts the age of the fossils at Quebrada Honda in the range of 12.5 to 13 million years ago.
Though the finds were limited to one fossil each, the teeth provide the telltale features needed to determine their kin and identify them as unique.
Mesoprocta hypsodus is related to agoutis and acouchis, two types of current and common rodents found from Costa Rica to Brazil. Tall, complex teeth are typical of these rodents, which are known for their flatish face, long legs and quickness.
Based on the d
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Case Western Reserve University