image

(Monday) researchers from the University of Tasmania, Queensland Museum and La Trobe University announced Australia’s second dicynodont had been described, using a 250 million-year-old fossilised piece of tusk and upper jaw.

The find is significant, as it confirms the theory that the dicynodont, considered a distant ancestor of mammals, existed across the globe. It also further erodes the idea that Australia had unique fauna.

The discovery of the fossil in Tasmania also provides another clue as to why the remnants of the species have been found only once previously in Australia. Lodged in sedimentary rock on the Tasman Peninsula south-east of Hobart, the dicynodont fossil (pictured) was found below the high-tide mark.

”I think it’s more than likely that there was more there but it’s just been washed away over time,” said Queensland Museum head of geosciences Andrew Rozefelds.

The size of the remains suggests the animal had a skull 25-30 centimetres long and a body about the size of a cow. The tusks would have measured up to 15 centimetres long.

”Arguably it’s probably one of the largest land animals ever to have been found in Tasmania,” Dr Rozefelds said.

Sedimentologist Stuart Bull from the University of Tasmania said it appeared the animal had not died where it was found. He said the type of sedimentary rock suggested it was ”high energy”, meaning characterised by fast-flowing rivers and streams with strong currents. This increases the chance of damage to animal remains – and ultimately evidence that the creature roamed Australia’s temperate forests.

”I suspect that the dicynodont bones are fairly robust fragments and that they died somewhere on the plain before being transported downstream to the area where we found them,” Dr Bull said.

Complete dicynodont specimens have been found in India and South Africa. The proportions of other fossils suggests the species ranged in size from a large guinea pig to a cow. Fossils found in South Africa point to a wombat-sized creature that lived in a burrow, boosting the chance of the skeleton being protected from predation and the elements.

”In contrast, I think our larger creatures were out roaming, eating the vegetation and probably dying in the open, which is why we don’t find such a good record of them here,” Dr Bull said.

The findings have been published in the Journal of Vertebrate Palaeontology.

Read more: http://www.theage.com.au/national/prehistoric-fossil-confirms-tusked-mammal-ancestor-20111219-1p2ew.html#ixzz1h0sbROZW