It has long been a matter of debate whether the thylacine, or Tasmanian tiger, was native to Australia or the survivor of ancient South American marsupial wolves, or borhyaenids. Thylacines bore great similarity to borhyaenids, which in turn resembled modern dogs and wolves. Yet many have maintained that they were not borhyaenids, but had evolved from the same ancestors as a group of modern Australian marsupial predators, the dasyurids.

Dasyurids include the Tasmanian devil, quolls ("native cats"), dunnarts, antechinuses, brush-tailed phascogales, and tiny planigales. Because of the great difference in size and appearance, many doubted this relationship existed. And then there was the fact that thylacines bore such a resemblance to borhyaenids (which vanished 5 million years ago after placental predators entered South America via the new land bridge formed by the Isthmus of Panama).

However, in 1981, a piece of skin from a 2000 year old mummified thylacine (found in a limestone cave on the Nullabor Plain, WA) was DNA tested and the borhyaenid link was ruled out. So it seems their similarities were a result of convergent evolution, the evolutionary force that creates similar animals to fill in similar niches. We know there were sabre toothed marsupial tigers as well as the placental variety. Borhyaenids were South America's dog-like predator till their placental counterparts came. So it seems that thylacines evolved from Australian stock, molded by convergent evolution.

But until recently, this has all been speculation, as there was still the fact that thylacines differed from dasyurids, so the ancestor was unclear. This is all about to change as Sydney zoologist Dr Jeanette Muirhead (School of Biological Sciences, University of NSW) has found fossils spanning from between 10 million and 25 million years ago. At least 6 new species of thylacine were discovered in the limestone rocks of Riversleigh Station, north-western Queensland. This shows they were a successful and diverse group of Australian predators. What's more, the dasyurid connection has now been confirmed, as the fossilised thylacines ranged from large, dog-like predators down to ones the size of quolls and marsupial mice.

Click hereto read about another animal that was thought to be more South American than Australian (till now), and that was also killed off by humans.....