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Press Release: Fossil of Largest Known Platypus Discovered in Australia


Bethesda, MD – No living mammal is more peculiar than the platypus. It has a broad, duck-like bill, thick, otter-like fur, and webbed, beaver-like feet. The platypus lays eggs rather than gives birth to live young, its snout is covered with electroreceptors that detect underwater prey, and male platypuses have a venomous spur on their hind foot. Until recently, the fossil record indicated that the platypus lineage was unique, with only one species inhabiting the Earth at any one time. This picture has changed with the publication of a new study in the latest issue of the Journal of Vertebrate Paleontology that describes a new, giant species of extinct platypus that was a side-branch of the platypus family tree.

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.

"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,” said PhD candidate Rebecca Pian, lead author of the study.

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.

“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,” said Dr. Suzanne Hand of the University of New South Wales, a co-author of the study. “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 modern platypus completely lacks teeth as an adult and instead bears horny pads in its mouth. The name Obdurodon comes from the Greek for “lasting (obdurate) tooth” and was coined to distinguish extinct toothed platypuses from the essentially toothless modern species.

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

The specific epithet of the new species, tharalkooschild, honors an Indigenous Australian creation story about the origin of the platypus. In the Dreamtime, Tharalkoo was a headstrong girl duck inclined to disobey her parents. Her parents warned her not to swim downriver because Bigoon the Water-rat would have his wicked way with her. Scoffing, she disobeyed her parents and was ravished by Bigoon. By the time Tharalkoo escaped and returned to her family, the other girl ducks were laying eggs, so she did the same. But instead of a fluffy little duckling emerging from her egg, her child was an amazing chimera that had the bill, webbed hind feet, and egg-laying habit of a duck, along with the fur and front feet of a rodent—the first Platypus.

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Click here to view this press release in Spanish.

About the Society of Vertebrate Paleontology
Founded in 1940 by thirty-four paleontologists, the Society now has more than 2,300
members representing professionals, students, artists, preparators, and others interested in
VP. It is organized exclusively for educational and scientific purposes, with the object of
advancing the science of vertebrate paleontology.

Journal of Vertebrate Paleontology

The Journal of Vertebrate Paleontology (JVP) is the leading journal of professional
vertebrate paleontology and the flagship publication of the Society. It was founded in 1980
by Dr. Jiri Zidek and publishes contributions on all aspects of vertebrate paleontology.

For complimentary access to the full article, visit: http://www.tandfonline.com/toc/ujvp20/33/6
The article appears in the Journal of Vertebrate Paleontology 33(6) published by Taylor and
Francis Citation: Pian, R., M. Archer, and S.J. Hand. 2013. A new, giant platypus, Obdurodon
tharalkooschild, sp. nov. (Monotremata, Ornithorhynchidae), from the Riversleigh World
Heritage Area, Australia. Journal of Vertebrate Paleontology 33(6):1-5.

Journal Web site: Society of Vertebrate Paleontology: http://www.vertpaleo.org

AUTHOR CONTACT INFORMATION
Rebecca Pian (rpian@amnh.org) PhD candidate, Columbia University and American
Museum of Natural History

Dr. Michael Archer (m.archer@unsw.edu.au) Professor of Biological Science, University of
New South Wales

Dr. Susan Hand (s.hand@unsw.edu.au) Associate Professor of Biological Science,
University of New South Wales

OTHER EXPERTS NOT DIRECTLY INVOLVED WITH THE STUDY

Dr. Ernest Lundelius (erniel@autexas.edu), University of Texas, familiar with Australian palaeontology and the Riversleigh World Heritage Area

Dr. Phil Gingerich (gingerich@umich.edu), University of Michigan, specialist in mammalian evolution, familiar with Riversleigh World Heritage Area

Dr. Tom Grant (t.grant@unsw.edu.au), University of New South Wales, Australia, world expert on the living Platypus

Dr. Marcelo Sanchez (m.sanchez@pim.uzh.ch), University of Zurich, Switzerland, specialist in evolution of Southern Hemisphere mammals


Image 1. Obdurodon tharalkooschild, a middle to late Cenozoic giant toothed platypus from the the World Heritage fossil deposits of Riversleigh, Australia. At about one meter (more than 3 feet) in length and with powerful teeth (inset: the holotype, a first lower molar), it would have been capable of killing much larger prey, such as lungfish and even small turtles, than its much smaller living relative. Reconstruction by Peter Schouten.

    Image 2. First lower molar of the new giant platypus, Obdurodon tharalkooschild. Photo by R. Pian.


Image 3. Richly fossiliferous freshwater limestones in the Riversleigh World Heritage Area. Photo by M. Archer.


Image 4. Marking positions of fossil mammals at the Riversleigh World Heritage Area. Photo by H. Godthelp.


Image 5. Excavating ancient mammal fossils at the Riversleigh World Heritage Area. Photo by H. Godthelp.


Image 6. Sixty-one million years of platypus evolution. A, Monotrematum sudamericanum from the Paleocene of Patagonia (63-61 million years old; by James McKinnon); B, Obdurodon dicksoni from the middle Miocene of Riversleigh, Queensland (15 million years old; by Peter Schouten from Schouten et al. Antipodean Ark, in prep.); C, Obdurodon tharalkooschild n. sp. from Riversleigh, Queensland, possibly late Miocene/Pliocene in age (by Peter Schouten); D, The living platypus, Ornithorhynchus anatinus from eastern Australia (by Rod Scott). All species have functional teeth except the living species, which is the smallest and last surviving member of its family.



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