Scientists in Chile have discovered the fossil of a minute, mouse-sized mammal believed to have lived during the age of dinosaurs in the region of Chilean Patagonia.
Identified as Yeutherium pressor, the creature is estimated to have weighed between 30 and 40 grams—approximately one ounce—and is believed to have existed during the Upper Cretaceous period, some 74 million years ago.
It is the smallest mammal ever uncovered in this part of South America, dating from a time when the area formed part of the ancient landmass known as Gondwana.
The fossil consists of a small section of jaw containing one molar and the crown and roots of two additional molars. Hans Püschel, who led the team of researchers from the University of Chile and the Millennium Nucleus research centre, confirmed the details of the find.
The discovery was published this month in the British scientific journal Proceedings of the Royal Society B.
Researchers located the fossil in the Río de las Chinas Valley, situated in the Magallanes Region of southern Chile, approximately 3,000 kilometres south of Santiago.
Despite its rodent-like appearance, Yeutherium pressor was a mammal that most likely laid eggs—similar to the platypus—or carried its young in a pouch, as seen in kangaroos and opossums.
The morphology of its teeth suggests a diet comprising relatively hard vegetation.
Like the dinosaurs it once shared its environment with, this tiny mammal became extinct abruptly at the close of the Cretaceous period, around 66 million years ago.
