Asunción, Paraguay – Riso Cave in the Paraguayan Chaco has been seen as an unspoiled treasure by paleontologists ever since rodent remains were unexpectedly found there next to the fossil of a giant sloth of the Pleistocene Epoch.
The discovery of five jaws measuring 1.5 centimeters (3/5 of an inch) each and with almost all their molars intact, from four diminutive rodent species that lived around 10,000 years ago, constitutes the first fossil find of this type in Paraguay.
"It is of incalculable value because a study of the remains will help us understand what these rodents fed on, and so find out how the climate and vegetation in the region evolved," Victór Filippi, a researcher with the Universidad Nacional in Asunción, told Efe.
The area is an ecotone, as the merging of several ecosystems is known - in this case the Chaco, which is dry, and the Cerrado, made up of forests and pastureland.
Filippi and his team found the fossil remains of the small mammals - Graomys chacoensis, Oligoryzomys, Holochilus chacarius and Calomys - while studying the remains of a giant sloth (Catonyx cuvieri), which they discovered two years ago.
Until then it was believed that the species, long since extinct, had lived only in Brazil and Uruguay.
Also found inside Riso Cave, located near the city of Vallemi some 610 kilometers (380 miles) north of Asuncion, were the osteoderms, or bony plates, of a crocodile.
An act of vandalism, however, left the sloth skeleton badly damaged soon after it was discovered.
The cave, some 40 meters (130 feet) deep, is located in the only karst, or limestone, terrain in Paraguay, around Vallemi, also known as "the cement capital," since a number of cement and lime-mining companies operate there.
And here is where the obstacles to the research arise.
One of those companies, Calera Riso, owns the cave and has refused permission for further exploration, after giving the go-ahead in the days when the giant sloth was found.