What’s more bizarre-looking than a platypus? How about a mega platypus? Published in the Journal of Vertebrate Paleontology, researchers write about having unearthed what they dubbed “platypus-zilla” in Queensland, Australia. Finding this fossil leads scientists to believe its evolutionary path may be more complicated than the animal’s appearance.

“It indicates there are branches in the platypus family tree that we hadn’t suspected before,” said Professor Mike Archer from the University of New South Wales. “Suddenly up pops ‘playtpus-zilla’ – this gigantic monstrosity that you would have been afraid to swim with.

The fossil of the platypus-zilla that was found was a single fossilized tooth, which was unearthed in the Riversleigh fossil beds in northern Queensland. Based on the tooth’s size, paleontologists were able to estimate the prehistoric beast to be about three feet long, twice the size of today’s platypus.

Paleontologists also estimate the ancient platypus to have waddled the Earth around 15 million years ago. During that time, the area—which today is a desert—would have been a lush forest. The tooth has a particular bump pattern that, along with the fossils found around it, lead the researchers to believe it ate turtles, crustaceans and other aquatic animals.

“Obdurodon tharalkooschild was a very large platypus with well-developed teeth,” Suzanne Hand of the University of New South Wales, a co-author of the study, said in a statement, “and we think it probably fed not only on crayfish and other freshwater crustaceans, but also on small vertebrates including the lungfish, frogs and small turtles that are preserved with it in the Two Tree Site fossil deposit.”

Because the researchers were only able to find the tooth, they cannot definitively say what the animal looked like exactly, but they do have their guesses.

“I guess it probably would have looked like a platypus on steroids,” said Archer.

Finding any fossils of this species is extremely rare, and so major gaps exist in its history and evolution.

“The discovery of this new one was a bit of a shock to us,” said Archer. “It was a wake-up call that the platypus’s story, the more we know about it, is increasingly more complicated than we thought.”

According to Science Daily, the oldest platypus findings date back some 61 million years, discovered in southern South America. Discovering this 15-million-year-old fossil of Obdurodon tharalkooschild indicates to researchers that the platypus became smaller through the millennia until it became what we see today.