A dinosaur bone discovered in Australia has defied prevailing wisdom about how the world's continents separated from a super-continent millions of years ago, a new study published on Tuesday said.

The 19-centimetre (eight-inch) bone was found in southeastern Australia but it comes from a very close cousin to Megaraptor, a flesh-ripping monster that lorded over swathes of South American some 90 million years ago.

The extraordinary similarity between the two giant theropods adds weight to a dissident view about the breakup of a super-continent, known as Gondwana, that formed the continents of the southern hemisphere, the authors say.