However, a newly discovered extinct 3-foot-long platypus suggests multiple species of the mixed-up mammals swam ancient Australian waters at the same time.
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"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 Michael Archer of the University of New South Wales, a co-author of the study that described the giant platypus in the Journal of Vertebrate Paleontology, in a press release. "Now we realize that there were unanticipated side branches on this tree, some of which became gigantic."
All that remains of the giant platypus, named Obdurodon tharalkooschild, is a single tooth. The tooth dates to between five and 15 million years ago. Like much of the rest of the playtpus, the tooth was unique enough to identify the creature and hint at its lifestyle.