Scientists have uncovered the fossil of a tiny, mouse-sized mammal dating back 74 million years to the Upper Cretaceous period in Chilean Patagonia. This mammal, identified as Yeutherium pressor, lived alongside dinosaurs during that era. The fossil discovery provides insight into the region's prehistoric fauna and represents the smallest known mammal from that time and area. The find has attracted international attention from paleontologists and researchers studying the evolution and diversity of mammals during the age of dinosaurs.