Scientists have found a tooth fossil belonging to an extinct species of platypus known as 'platypus-zilla.'

Researchers from the University of New South Wales unearthed the fossil from the Two Trees Site in the Riversleigh World Heritage Area in northwest Queensland. The molar tooth belongs to the platypus species dubbed as 'platypus-zilla.' It is twice as large as the platypus that exists today.

"We'd never seen anything this big so it really knocked our socks off to think that platypus could get this big," Prof. Michael Archer told Sky News.

"Platypus Godzilla. You can imagine the humorous scenes where somebody looks at the modern platypus and says 'That's not a platypus' and then picks up this monster and says 'That's a platypus'."

The study published in the Journal of Vertebral Paleontology has suggested that the platypus has full set of teeth unlike the living species, which only has horny pads in its mouth. The wear on the found tooth also suggests that the animal was crushing on its prey rather than cutting through them; and that it probably fed on animals living near them in swamps and lakes, such as crawfish, frogs and small turtles. This means that the site where the fossil was found is far from the desert that it is today, as it was likely a swampy area millions of years ago.

But with only one tooth fossil found, the researchers find it hard to figure out exactly what the platypus-zilla looked like back then; although previously found fossils indicate that they do look like the living species.

"I guess it probably would have looked like a platypus on steroids," Associate Prof. Suzanne Hand told the BBC.

The discovery of the new species, according to Prof. Archer, "was a bit of a shock to us. It was a wake-up call that the platypus's story, the more we know about it, is increasingly more complicated than we thought."

"Now we realize that there were unanticipated side branches on this tree, some of which became gigantic."