Tiny Dinosaur-Era Mammal Fossil Unearthed in Patagonia
Fossil of “Yeutherium pressor” Reveals Ancient South American Life
Scientists in Chile have unearthed the fossilized remains of a minuscule mammal that roamed the Earth alongside dinosaurs millions of years ago.
A Glimpse into Gondwana’s Past
This newly identified creature, named “Yeutherium pressor,” weighed a mere 30 to 40 grams – comparable to a modern-day mouse. It inhabited the region during the Upper Cretaceous period, approximately 74 million years ago, a time when South America was part of the vast supercontinent Gondwana.
Remarkable Fossil Discovery
The significant find consists of a fragment of jawbone containing a molar, along with the crowns and roots of two other teeth. Hans Puschel, who spearheaded the research team from the University of Chile and Chile’s Millennium Nucleus center, described the fossil’s composition.
“a small piece of jaw with a molar and the crown and roots of two other molars,”
—Hans Puschel, Lead Researcher
The discovery, detailed in this month’s edition of the prestigious journal *Proceedings of the Royal Society B*, was made in the Rio de las Chinas Valley, situated roughly 3,000 kilometers south of Santiago, Chile.
Unique Mammalian Traits
Despite its rodent-like appearance, “Yeutherium pressor” likely reproduced by laying eggs, similar to modern monotremes like the platypus, or by nurturing its young in a pouch, akin to marsupials. Analysis of its teeth suggests a diet consisting primarily of harder plant matter.
Like the colossal dinosaurs with whom it shared its existence, this diminutive mammal faced a sudden extinction event at the close of the Cretaceous period, about 66 million years ago.
The fossil record of mammals from this era is sparse, making this discovery particularly valuable. For context, paleontologists estimate that over 60% of mammal species alive today have evolved significantly since the Cretaceous-Paleogene extinction event that wiped out the non-avian dinosaurs (Natural History Museum).
