No one will be intimidated by a platypus, which is roughly 15 inches in length. However, about 5 to 15 million years back, our ancestors coming face to face with an Obdurodon tharalkooschild might have had a different story to tell. It is a platypus about a meter long that roamed the lush forest of Australia and waded in its bodies of fresh water. And loved fresh meat.

A new research about the extinct, huge critter was fleshed out by scientists from the University of New South Wales in Australia from a single tooth excavated from a World Heritage Site in Riversleigh, Queensland, that is known for  its fossil deposits.

"Discovery of this new species was a shock to us because prior to this, the fossil record suggested that the evolutionary tree of platypuses was a relatively linear one. Now we realize that there were unanticipated side branches on this tree, some of which became gigantic," said Professor Mike Archer, one of the proponents of the research, in an interview.

Archer, together with his fellow scientists Rebecca Pian and Sue Hand, published their study that describes the tooth of the giant platypus species, Tuesday, in the Journal of Vertebrate Paleontology.

Prior to the discovery of the Obdurodon tharalkooschild, several species of platypus have been described. American scientists Richard Tedford and Michael Woodbourne reported in 1975 about an ancient platypus teeth fossil they discovered in central Australia. They traced the teeth to be from a platypus that roamed the region 24 to 26 million years ago. They called it Obdurodon insignis. The name distinguished the specie from the modern-day platypus that are toothless when they reach maturity.

Another species, Obduron dicksoni, was traced to belong to a platypus species that existed roughly 15 million years ago. It was based on a set of teeth also found in Riversleigh.

The newest find, the Obdurodon tharalkooschild is the biggest of known platypus to have existed. It is almost twice the size of the platypus humans know today.

The single tooth of the giant platypus was actually sort of forgotten until Rebecca Pian, a doctoral student in Columbia University, brought it out of storage.

I said, 'Wait a second, not only is it quite big, it's quite different as well," said Pian in an interview. Her colleagues agreed that indeed the tooth belong to an unknown species.

"...the evolution of the platypus is potentially more complicated than we thought," Pian added.

The tooth was bigger than any other tooth the team has seen before. The shape gave away that it belonged to a platypus but some of its features such as ridges and bumps were all new to the group. Archer and his team compared the tooth with other platypus samples and estimated the size of the new species of platypus.

The tooth of the O. tharalkooschild suggest that it could have eaten bigger preys such as frogs compared to the soft invertebrate diets of other platypuses.

The discovery also suggest the more complex evolution of Australia's fauna and the more diverse evolution of the platypus.