'Godzilla platypus' fossil discovered in Australia

This image shows Obdurodon tharalkooschild, a middle to late Cenozoic giant toothed platypus from the the World Heritage fossil deposits of Riversleigh, Australia. At about one meter (more than 3 feet) in length and with powerful teeth (inset: the holotype, a first lower molar), it would have been capable of killing much larger prey, such as lungfish and even small turtles, than its much smaller living relative.
Reconstruction / Illustration by Peter Schouten

Paleontologists have long believed that the platypus is one of the few species that can trace a direct line back to the beginning of time. Now, a new study is changing that image.

Researchers say a tooth discovered in the Riversleigh World Heritage Area in Queensland, Australia, belongs to a different, extinct platypus species.

"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 relatively linear one," Dr. Michael Archer of the University of New South Wales, a co-author of the study, said in a statement. "Now we realize that there were unanticipated side branches on this tree, some of which became gigantic."

Archer named the species "Platypus Godzilla" because it was up to twice the size of the modern platypus, growing up to three feet long. Its scientific name is Obdurodon tharalkooschild.

Published in the latest issue of the Journal of Vertebrate Paleontology, their examination of the tooth suggests that these godzillas lived between 15 and 5 million years ago. The teeth also indicate that it would have been able to feed on a range of other species.

"Obdurodon tharalkooschild was a very large platypus with well-developed teeth, 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," Dr. Suzanne Hand of the University of New South Wales, a co-author of the study, said in a statement.

The new species most likely does not have a direct ancestor. Before this discovery, the fossil record indicated that one species of platypus has existed throughout time, slowly evolving into the smaller, toothless version that lives today. In place of teeth, the modern platypus has horny pads in its mouth.

"Like other platypuses, it was probably a mostly aquatic mammal, and would have lived in and around the freshwater pools in the forests that covered the Riversleigh area millions of years ago," Hand said of the new species.

This is the fifth new species identified in Australia in less than a month, coming on the heels of the discovery of frogs that mate in the rain, a leaf-tailed gecko, and a skink in the Cape York Peninsula. Perhaps the most eye-catching was the discovery of the humpback dolphin, living off the coast of the island nation.

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    Danielle Elliot is a freelance science editor and reporter for CBS News. She holds an M.A. in science and health journalism from Columbia University and a B.A. in broadcast journalism from the University of Maryland. Follow her on Twitter - @daniellelliot.