It's possible that the platypus is the coolest mammal on Earth. Not only do they lay eggs, they are venomous and look like the bizarre product of a beaver/duck/otter orgy. A new paper from the University of New South Wales to be published in the Journal of Vertebrate Paleontology describes the discovery of a giant ancient platypus that is nearly twice the size of platypuses seen today and it even stands to rewrite what we thought we knew about their evolutionary lineage.

The discovery is of a single tooth and the researchers estimate the animal's size at approximately one meter. Modern platypuses are about the size of a house cat, making their ancient relatives approximately double their size. The tooth was found in limestone at the Riversleigh World Heritage fossil site in Queensland, Australia, not far from modern day platypus territory. The fossil is currently estimated at 5-15 million years old, though radiometric dating will be needed to confirm the age.

The fossil tooth is sharp and different morphological features indicate that the ancient platypus was a formidable predator that probably dined on crustaceans, fish, and possibly even turtles. This is considerably different from the platypus diet today. Today’s platypuses only have teeth early in life. As they mature, the teeth fall out and a spiky pad forms inside the mouth to grind up worms and shellfish, while gravel is also scooped up into the mouth to help break down the food.

The new giant platypus will greatly alter what is known about the evolutionary history of the platypus. Up until now, the lineage was thought to be fairly straightforward as one species gradually evolved into the next, but this discovery shows unexpected branching in the phylogenetic tree that resulted in very large animals.

The newly discovered species is being called Obdurodon tharalkooschild. “Obduron” is Greek for “lasting tooth” and the specific name is a nod to Tharalkoo, a character in the Australian folk story about a duck who is mated by a water rat. The emerging offspring had a blend of the traits of the two creatures and were the first platypuses.