Ancient Platypuses Had Teeth and Swam with Dolphins

The platypus has always been nature’s oddball—a mammal that seems to have been assembled from spare biological parts. But here’s what makes it even stranger: its ancient cousins were actually *more* normal, not less. And they hung out with dolphins in the Australian outback.

Paleontologists at Flinders University in Adelaide have just announced the discovery of new fossils belonging to *Obdurodon insignis*, a toothed ancestor of today’s platypus that lived around 25 million years ago during the late Oligocene period. The find, described in the journal Australian Zoologist, is genuinely rare—platypuses almost never show up in the fossil record, and when they do, it’s usually just teeth or jaw fragments. This time, the team found enough material to paint a fuller picture of how these creatures actually lived.

The most striking difference between *Obdurodon insignis* and modern platypuses? Teeth. Real, functional molars and premolars that could crush through hard-shelled prey like yabbies (freshwater shrimp). Today’s platypuses lose their vestigial teeth shortly after birth and rely on a small horny pad to chew instead. But that ancient version? Dr. Aaron Camens of Flinders University explains that the new premolar fossils reveal *Obdurodon insignis* had large, pointed front teeth alongside robust molars—a serious set of gnashers built for crushing animals with shells or tough exoskeletons. The rest of its anatomy—revealed through a well-preserved scapula—suggests it swam and moved like its modern descendant, just slightly larger and far more dentally equipped.

What really captures the imagination is the ecosystem these creatures inhabited. Picture central Australia 25 million years ago: not the arid outback we know today, but a landscape of huge lakes, slow-flowing rivers, and forested lowlands teeming with life. The trees hosted diverse arboreal mammals like koalas and possums, while the giant eagle Archaehierax hunted from above. On the ground, sheep-sized marsupials browsed. Below the surface, lungfish and smaller species filled the lakes. And there, swimming alongside these other animals, was something unexpected: a small dolphin. A *freshwater* dolphin, living in an ancient ecosystem that’s now long vanished.

In this lost world, the toothed platypus swam with the dolphins—a snapshot of a community that dissolved over millennia as the climate shifted and the rainforests gave way to desert. What’s remarkable is that platypuses never left. They’ve been continuously swimming in Australian waterways ever since that ancient community dissolved, making them one of the most durable mammalian lineages on the continent. Professor Trevor Worthy, the study’s co-author, captures the thrill perfectly: for over 20 years, his team has been returning to this remote location east of the Flinders Ranges, excavating rocks and collecting fossils. From more than a thousand fossils found, only three belong to the toothed platypus. Each one is a small window into a vanished world—and proof that sometimes, the strangest animals have the deepest histories.