Around 70 million years ago, a small, furry, platypus-like creature shuffled along the banks of an ancient lake. This would not have been a remarkable occurrence, except for one thing: The lake was in present-day Argentina, not Australia.
The creature, dubbed Patagorhynchus pascuali, is the oldest fossil of the egg-laying mammal group known as monotremes ever discovered in South America. The discovery may rewrite the story of where these oddball early mammals evolved. Today, all five species of living monotremes — which include the platypus (Ornithorhynchus anatinus), the short-beaked echidna (Tachyglossus aculeatus) and three species of long-beaked echidnas (Zaglossus) — are found exclusively in Australia and a few of its surrounding islands. So how did a platypus ancestor wind up so far from Down Under?
Millions of years ago, Australia, South America and Antarctica (as well as parts of Africa and Asia) were smooshed together in a supercontinent called Gondwana. This mega landmass began to break up about 180 million years ago, during the Jurassic period, but didn't fully separate until about 66 million years ago, at the end of the Cretaceous period.
