An Australian-U.S. team of paleontologists has found a unique fossil of a huge, carnivorous platypus that lived in what is now Australia during the late Miocene.
This is an artist’s reconstruction of Obdurodon tharalkooschild. The inset shows its first lower molar. Image credit: Peter Schouten.
The modern platypus is a duck-billed, venomous, semi-aquatic mammal with webbed feet and is covered in short waterproof fur. It is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth.
The new extinct species of platypus, named Obdurodon tharalkooschild, has been described from a unique tooth fossil found at the famous Riversleigh World Heritage Area of Queensland.
The specific name, tharalkooschild, honors an Indigenous Australian creation story about the origin of the platypus.
Unlike the living species, Obdurodon tharalkooschild had fully functional teeth that may have been used to kill and consume a wide range of animals that lived alongside it in ancient pools and lakes. Based on the size of its tooth, it is estimated that Obdurodon tharalkooschild would have been twice the size of the modern platypus, around 3.3 feet (1 m) long.
“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,” explained Prof Suzanne Hand from the University of New South Wales, a co-author of the article published in the Journal of Vertebrate Palaeontology.
“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 modern platypus completely lacks teeth as an adult and instead bears horny pads in its mouth; Obdurodon tharalkooschild is unlikely to have been its immediate ancestor.
Toothed platypuses, Monotrematum sudamericanum, lived in what is now South America until 61 million years ago.
The oldest extinct platypus found in Australia was 26-million-year-old Obdurodon insignis. A larger species, Obdurodon dicksoni, was found in 19 to 15 million year old deposits at Riversleigh, and the remains include the only known fossil platypus skull.
While many of Riversleigh’s fossil deposits are now being radiometrically dated, the precise age of the particular deposit that produced the new species, Obdurodon tharalkooschild, is in doubt but is likely to be between 15 and 5 million years old.
______
Bibliographic information: Pian R et al. 2013. A new, giant platypus, Obdurodon tharalkooschild, sp. nov. (Monotremata, Ornithorhynchidae), from the Riversleigh World Heritage Area, Australia. Journal of Vertebrate Paleontology 33 (6)
