An indigenous Australian legend has it that the first platypus was the odd offspring of a duck named Tharalkoo and a rat. In a nod to the tale, researchers have named a newly identified ancient giant platypus species Obdurodon tharalkooschild. All that was found of the creature was a single tooth at a site in Queensland, estimated to be between 5 million and 15 million years old. The molar (above, right) shows wear that indicates that the platypus probably crushed hard-shelled prey, like turtles (above, left), also found fossilized at the site. Modern adult platypuses do not have teeth, but their ancestors did. Based on a comparison of the size of the molar to the teeth of other extinct platypuses, the team reports today in the Journal of Vertebrate Paleontology that O. tharalkooschild was probably about a meter long—bigger than any other platypus and twice the size of the species alive today. Finding a new species of platypus was a surprise: Previously, researchers thought that the creatures had a single branch on their family tree, with no more than one distinct species alive at any time. Despite its origin-story namesake, the new platypus is a cousin of the lineage of relatively small platypuses that led to the duck-mammal mash-up of today—probably one of several in a now-extinct side branch of giant platypuses.

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