The story of the previous posts is that tree-kangaroos came from rock-wallabies that evolved to take advantage of an abundant and underutilized Malesian flora that invaded Australia in the mid-Miocene.  The slight hiccup in this tale is that the Malesian flora did not extend a long way either south or west into the Australian continent (Sniderman and Jordan, 2011).  This might seem to be of little consequence until we take into account the existence of Bohra.  As you will recall, fossils of these large, assumed ancestral tree-kangaroos were found as far west and south as the Nullabor Plain, a long way from the proposed site of tree-kangaroo evolution.
This is puzzling. If these were in fact ancestral, why were they so far away and why are there no refugial populations of tree-kangaroos anywhere else in Australia? The Malesian flora certainly didn't extend that far.  Maybe the answer lies once again with rock-wallabies...
Rock-wallabies are widespread and their proposed ancestral range encompassed all the sites where Bohra fossils have been found (Fig. 1).

Figure 1. Current (coloured areas) and ancestral (within dashed line) ranges of the genus Petrogale.  Source: Potter et al, 2012

A recent molecular phylogeny constructed for Petrogale concluded that this genus originated in a mesic environment within Australia (characteristic of the East Coast today, also the area the basal Proserpine Rock-Wallaby calls home) and dispersed into more arid environments from the Late Miocene on. From here, further diversification happened during the Plio-Pleistocene when it was likely that glaciation caused repeated range contractions and resulted in isolated refugia.  The current arid-adapted taxa are considered to have arisen quite recently, allowing the persistence of Petrogale in the arid central and western regions of Australia (Potter et al, 2012).

If we adopt the assumption for now that rock-wallabies originated somewhere around the current range of P.persephone and radiated out, then perhaps it is not drawing too long a bow to suggest that ancestral tree-kangaroos followed a similar route, adapting to different food resources as they went.  The difference in current distribution of the two groups can be probably explained by the ability of Petrogale to adapt to forest contraction and aridfication, which of course would have severely disadvantaged tree-kangaroos.  Remember that the Nullarbor plain was treed when Bohra was roaming the land there (Prideux and Warburton, 2008) so perhaps this contraction of habitat has been a feature of tree-kangaroo evolution from the early days.




Sniderman, J. M., & Jordan, G. J. (2011). Extent and timing of floristic exchange between Australian and Asian rain forests. Journal of Biogeography,38(8), 1445-1455.


Potter, S., Cooper, S. J., Metcalfe, C. J., Taggart, D. A., & Eldridge, M. D. (2012). Phylogenetic relationships of rock-wallabies, Petrogale (Marsupialia: Macropodidae) and their biogeographic history within Australia. Molecular Phylogenetics and Evolution, 62(2), 640-652.

Prideaux, G. J., & Warburton, N. M. (2008). A new Pleistocene tree-kangaroo (Diprotodontia: Macropodidae) from the Nullarbor Plain of south-central Australia. Journal of Vertebrate Paleontology, 28(2), 463-478.