Obdurodon tharalkooschild
November 5, 2013

Fossil Leads To Discovery Of Largest-Ever Platypus Species

redOrbit Staff & Wire Reports - Your Universe Online

The discovery of a lone tooth in the Riversleigh World Heritage Area of Queensland, Australia, has led to the classification of a new, giant, now-extinct species of platypus known as the Obdurodon tharalkooschild.

The new species in the duck-billed, egg-laying mammal’s family is detailed in the latest edition of the Journal of Vertebrate Paleontology, and while the precise age of the fossil has not been yet been determined, it is believed to be between five and 15 million years old.

Based on the size of the tooth, it is believed that this ancient platypus species would have been more than three feet long – twice the size of the modern version of the mammal. Furthermore, bumps and ridges discovered on the tooth also helped researchers determine what types of food the creature would likely have eaten.

“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,” explained study co-author Dr. Suzanne Hand, an associate professor at the University of New South Wales.

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,” she added.

Previously, the fossil record suggested that the lineage of the platypus was unique, and that only one species lived at any given time. The newly discovered species would have been a “side-branch” of the creature’s family tree, the researchers said.

Prior to the discovery of Obdurodon tharalkooschild, fossils discovered in South America and Australia had scientists believing that the creatures (and their teeth) became smaller over time. In fact, the modern adult platypus has no teeth. Instead, its mouth contains horny pads.

“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,” said co-author Dr. Michael Archer of the University of New South Wales. “Now we realize that there were unanticipated side branches on this tree, some of which became gigantic.”

Monotremes (platypuses and echidnas) are the last remnant of an ancient radiation of mammals unique to the southern continents. A new platypus species, even one that is highly incomplete, is a very important aid in developing understanding about these fascinating mammals,” added lead author Rebecca Pian, a graduate student at Columbia University.

Image 2 (below): This is the first lower molar of the new giant platypus, Obdurodon tharalkooschild. Credit: Photo by R. Pian