Tilacino Potens

Source: derived from Long et al. 2002

Source: derived from Long et al. 2002

however, shows us that since the late Oligocene (some 24 million years ago) only two species of koala have co-existed at any one time. In terms of abundance, the scarcity of fossil evidence suggests that despite the decline in numbers through the 19th and 20th centuries, koala populations are larger now than at any point in their distant history.20 It is thought that before the ancestors of modern eucalypts evolved (some 24 million years ago), the koala lived in rainforests. During the mid- to late Miocene (10 to 5 million years ago), the development of a drier climate saw eucalypt-dominated woodlands spreading at the expense of rainforest, thus allowing the koala to expand its distribution and become more abundant.21

The fossil record also shows a considerable difference in size between the various genera of koala. Madakoala and Perikoala were similar in size to the modern species, while Nimiokoala and Litokoala were only half to two-thirds the size of a modern koala. Phascolarctosyorkensis, once placed in the genus Cundo-koala but now included in the same genus as the modern koala, was twice the size of the koalas we see today.22

Reconstruction of the Miocene koala Nimiokoala greystanesi from Riversleigh World Heritage area, north-western Queensland. (Anne Musser)

The differences between the modern koala and its fossil ancestors can be seen in the size and shape of the teeth, skulls and other bones. Professor Michael Archer and his team from the University of New South Wales in Sydney have found thousands of fossils in the Riversleigh World Heritage area, including one species of Nimiokoala, two species of Litokoala, and there appears to have been at least two other koalas or koala-like animals at various times during the Oligocene and Miocene periods.23

The fossil record suggests that koalas once enjoyed a considerably wider distribution than they do today. Fossils of the modern koala genus Phascolarctos have been found through eastern Australia, across southern Australia to south-west Western Australia and even into central Australia. Pleistocene fossils of Phascolarctos have been discovered in eastern South Australia near the Victorian border,24 and fossil remains from the

Riversleigh

Madakoala

Periloala

Nimiokoala

Riversleigh

Madakoala

Periloala

Nimiokoala

L. Oligocene 26-23.5

E. Miocene 23.5-16.4

M. Miocene 16.4-11

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  • aleardo
    What fossil evidence do we have for koalas?
    4 months ago

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