Giant turtle-devouring duck-billed platypus discovered

Jeremy Hance
mongabay.com
November 04, 2013



Based on a single tooth from Australia, scientists believe they have discovered a giant, meter-long (3.3 feet) duck-billed platypus that likely fed on fish, frogs, and even turtles, according to a new study in Journal of Vertebrate Paleontology. At least twice the size of a modern duckbilled platypus, the scientists say the extinct giant likely lived between 15 and 5 million years ago.

"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.

The modern duck-billed platypus (Ornithorhynchus anatinus) is one of the most bizarre animals on Earth. Although a mammal, the species is set a part by the fact that it lays eggs.In fact modern platypus and four species of echidna are the only survivors of a once widespread group of mammals (the Monotremes) that reproduce by laying eggs like reptiles. Moreover the platypus sports a duck-like bill, furry coat, and webbed feet. It's no wonder then that the first scientist to officially describe the species in 1799, British biologist George Shaw, initially thought the platypus was a well-played hoax.

This is the first lower molar of the new giant platypus, Obdurodon tharalkooschild. Photo by: R. Pian.
This is the first lower molar of the new giant platypus, Obdurodon tharalkooschild. Photo by: R. Pian.
Platypus are also one of the world's only venomous mammals: males have a venomous spur on their hind feet. To make matters even stranger, recent research has shown the platypus has no less than 10 sex chromosomes (most mammals have two). Its as-yet unfinished genome shows both mammal and reptile characteristics.

However, the new giant platypus, named Obdurodon tharalkooschild, had one large contrast with the modern duck-billed platypus aside from its girth: the prehistoric giant, as shown from the lone representaitve fossil, sported teeth. Modern duck-billed platypus lose all their teeth after a few days and adults grind their food between horny pads in its bills.

"Like other platypuses, [Obdurodon tharalkooschild] 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," explains co-author Suzanne Hand of the University of New South Wales. "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."

Researchers discovered the new species' tooth in the Riversleigh World Heritage Area in northwest Queensland, Australia.

The discovery of Obdurodon tharalkooschild upends our understanding of platypus evolution. Prior to this fossil, scientists believed platypus followed a single track, whereby the species gradually became smaller and smaller, and lost it's teeth. The oldest-known fossils of platypus come from 61 million years ago in South America, shortly after the mass extinction of the dinosaurs.

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

This image shows 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. Illustration by: Peter Schouten.
This image shows 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. Illustration by: Peter Schouten.



Modern duck-billed platypus. Photo by: Stefan Kraft.
Modern duck-billed platypus. Photo by: Stefan Kraft/Creative Commons 3.0.

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.
















AUTHOR: Jeremy Hance joined Mongabay full-time in 2009. He currently serves as senior writer and editor. He has also authored a book.




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CITATION:
Jeremy Hance
mongabay.com (November 04, 2013).

Giant turtle-devouring duck-billed platypus discovered.

http://news.mongabay.com/2013/1104-hance-giant-platypus.html