Scientists Uncover Fossil of Tiny Mammal in Chilean Patagonia

Scientists in Chile have discovered the fossil of a mouse-sized mammal that lived alongside dinosaurs around 74 million years ago in Chilean Patagonia.

Named Yeutherium pressor, the tiny creature weighed between 30 and 40 grams and is the smallest mammal ever found in this part of South America, which was then part of the ancient supercontinent Gondwana.

The fossil — a small jaw fragment containing one molar and the crown and roots of two others — was unearthed in the Río de las Chinas Valley, in the Magallanes region, some 3,000 kilometers south of Santiago.

Lead researcher Hans Puschel, from the University of Chile and Chile’s Millennium Nucleus center for early mammals, said the discovery sheds light on the region’s prehistoric biodiversity. The findings were published this month in the Proceedings of the Royal Society B.

Despite its rodent-like appearance, Yeutherium pressor likely laid eggs, like a platypus, or carried its young in a pouch, like kangaroos and opossums. The shape of its teeth suggests it fed on hard vegetation.

Like the dinosaurs it lived alongside, the tiny mammal disappeared in the mass extinction that ended the Cretaceous period around 66 million years ago.