Australia: The Land Where Time Began

A biography of the Australian continent 

Anatomy Based Relationships - Ankle bones

It has been proposed that the ankle bone could be used to differentiate the Australian marsupials from the American marsupials (Szalay, 1982). There was a single articular facet at the junction of the long bones and the bones of the ankle joint, but Szalay found 2 facets in the ankles of the 2 main American marsupial families. The monito del monte (Dromiciops gliroides, from Chile, was the only American species he found that had an undivided facet, as found in the Australian species. As a result of this finding, biologists began looking for closer links between the marsupials of Australia and those of America. Support for such a link has come from molecular studies. The similarity of ankle structure that Szalay based his distinction on has been found to be less consistent than he thought, though later research has confirmed the suggestion that Dromiciops is closer to species from Australasia than to those from America. Subsequent research on a much larger sample (Hershkovitz, 1992) found that both types of angle joint occur among both American and Australasian marsupial species.

1. Chris Johnson, Australia's Mammal Extinctions, a 50,000 year history, Cambridge University Press, 2006
2. M.Archer, S.J. Hand & H. Godthelp in Hill, Robert S., (ed.), 1994, History of the Australian Vegetation, Cambridge University Press.
3. Tyndale-Biscoe, Hugh, 2005, Life of Marsupials, CSIRO Publishing.