Researchers from Case Western Reserve University recently found the oldest fossils on the South American continent along the banks of the Ucayali River, an offshoot of the Amazon River.
The fossils, which are at least 41 million years old, are the teeth of mouse and rat-sized animals that experts say are most closely related to African rodents. They are from the suborder Caviomorpha, which means they are related to living species such as guinea pigs, chinchillas and New World porcupines.
