Monotreme fossil surprises scientists


February 11, 2005

A WORLD-first discovery of the jaw of a tiny creature related to the platypus was as surprising as that of the "hobbit" in Indonesia last year, a Melbourne scientist said today.

The 115 million-year-old fossil was found in rock on Victoria's south-east coast by a team of researchers and volunteers from Monash University and Melbourne Museum in 2002.

After 20 months of analysis, researchers today unveiled the 12mm-to-15mm-long jaw bone of the teinolophos trusleri.

The specimen is a monotreme like the platypus and echidna, which, unlike other mammals, lay eggs and lack whiskers, teeth and external ears.

"What is special about it is it has aspects that suggests monotremes split away from other mammals (such as the koala and wallaby) much earlier than we thought," the Melbourne Museum curator of vertebrate palaeontology, Tom Rich, said.

Until now, that transition was thought to have occurred only once about 140 million years ago.

"But what happened, on the basis of this fossil, is that it happened separately in the line leading to monotremes and the line leading to the marsupials (200 million years ago)."

Dr Rich said this phenomenon was called conversion evolution, where different ancestors produced the same evolutionary result.

He said this was something scientists had not expected and the discovery marked a key moment in the global study of animal evolution.

"In a way it is comparable to ... what they call the 'hobbit' found late last year," he said.

The world of archaeology was stunned last October with the discovery of a well-preserved skeleton of a fully grown female, barely a metre tall, in a cave on the Indonesian island of Flores.

The Monash research team had previously uncovered specimens of the teinolophos trusleri that were crushed, but this one was in pristine condition.

Dr Rich said the research team had been working at the Inverloch site since 1993 and would continue as long as funds kept flowing from the Australian Research Council.

But he said it had been searching for a new sponsor after the withdrawal of National Geographic.