Giant Platypus? Newly Discovered Fossil Tooth Reveals Largest Platypus on Record

But these Australian stream-and-river-dwelling mammals are actually quite small—at about a foot long, the “size of a small cat,” says Rebecca Pian, a first-year graduate student at Columbia University studying vertebrate paleontology, with fellowships from Columbia and the Richard Gilder Graduate School at the Museum.

At perhaps more than three feet long, this newly discovered, extinct platypus species is the largest described so far. Researchers infer the species' size from the discovery of a single tooth. 
Illustration by Peter Schouten

Having seen the living species, Pian, who is from Australia, and colleagues recently reported the discovery of a new fossil platypus species that, at more than 3 feet long, is far larger than any other platypus, fossil or living.  (The work is featured in the Journal of Vertebrate Paleontology.)

“It’s bigger than all of them,” says Pian of the new find, which is one of only four fossil platypus species known.

Pian and her colleagues discovered a single tooth of the species, which they named Obdurodon tharaklooschild, in the limestone rocks of the famed Riversleigh site in northwest Queensland, Australia.

At right, researcher Rebecca Pian investigates a piece of limestone for fossils. At left is Troy Meyers, of the University of New South Wales. 
Mark Taylor

Teeth, says Pian, provide a wealth of information for a paleontologist. By comparing this fossil tooth, estimated to be 15 to 5 million years old, with those of closely related fossils, the research team was able to infer the platypus’s likely size; they also concluded that the species’ diet may have included such small vertebrates as turtles and frogs.

By contrast, individuals from the only living platypus species, Ornithorhynchus anatinus, have no teeth as adults—instead, the adult animals have horny pads in their mouths and feed on soft invertebrates.

At the Museum, Pian is now working with her adviser John Flynn, Frick Curator of Fossil Mammals, dean of the Richard Gilder Graduate School, and an adjunct professor at Columbia, to investigate South American fossil marsupials—a different, far more diverse branch of mammals from the egg-laying monotremes, of which four species of echidna and the platypus are the only living representatives.

“This discovery is exciting," says Flynn, "because it greatly expands the known size diversity of a fascinating, but extremely poorly known, group of mammals."