The new platypus species, named Obdurodon tharalkooschild, is based on a single tooth from the famous Riversleigh World Heritage Area of northwest Queensland.
While many of Riversleigh's fossil deposits are now being radiometrically dated, the precise age of the particular deposit that produced this giant platypus is in doubt but is likely to be between 15 and 5 million years old.
Lead author PhD candidate Rebecca Pian said that the monotremes (platypuses and echidnas) are the last remnant of an ancient radiation of mammals unique to the southern continents.
Pian asserted that new platypus species, even one that is highly incomplete, is a very important aid in developing understanding about these fascinating mammals.
Based on the size of tooth, it is estimated that this extinct species would have been nearly a meter (more than three feet) long, twice the size of the modern platypus. The bumps and ridges on the teeth also provide clues about what this species likely ate.
Co-author Dr. Suzanne Hand of the University of New South Wales said that 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.
She said that 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.
The oldest platypus fossils come from 61 million-year-old rocks in southern South America. Younger platypus fossils are known from Australia in what is now the Simpson Desert. Before the discovery of Obdurodon tharalkooschild, these fossils suggested that platypuses became smaller and reduced the size of their teeth through time.
The study has been published in the Journal of Vertebrate Paleontology.
--ANI (Posted on 05-11-2013)