Phascolarctos cinereus, the koala, is a member of the Diprodontia. This taxon encompasses a large range of sizes and shapes and includes wombats, possums, wallabies, and kangaroos. These seemingly diverse animals posses a number of characters that unite them together, such as diprotodont dentition (the two midlle incisors of the lower jaw are greatly enlarged and project forward), syndactyly (the second and third digits fo the hindfoot are joined by skin), fewer than three upper incisors, and selenodont dentition.

The koala is found only in Australia from southeastern Queensland to eastern New South Whales and Victoria to southeastern South Australia. Their fossil record extends back to the mid-Miocene, and they seem to have occupied a more extended range. The koala primarily is noctural and spends most of its time in eucalyptus trees. Its diet consists largely of eucalyptus leaves, but it may also eat mistletoe or box leaves. Until the early twentieth century, the koala was ubiquitous in southeastern Australia. Hunting and habitat destruction, however, seems to be the primary contributors to its decline. The IUCN currently lists the koala as near threatened.

This specimen (TMM M-2946), exchanged from Monash University, Australia, is the skull of Phascolarctos cinereus. It was made available to the University of Texas High-Resolution X-ray CT Facility for scanning by Dr. Timothy Rowe of The University of Texas at Austin. Funding for image processing was provided by a National Science Foundation Digital Libraries Initiative grant to Dr. Rowe.

The specimen was scanned by Matthew Colbert on 22 August 2003 along the coronal axis for a total of 599 slices, each slice 0.238 mm thick with an interslice spacing of 0.238 mm.

Literature

Davison, C. V., and W. G. Young. 1990. The muscles of mastication of Phascolarctos cinereus (Phascolarctidae, Marsupialia). Australian Journal of Zoology 38:227-240.

Ellis, W. A., P. T. Hale, and F. S. Barboza. 2002. Breeding dynamics of koalas in open woodlands. Wildlife Research 29:19-25.

Grand, T. I., and F. S. Barboza. 2001. Anatomy and development of the koala, Phascolarctos cinereus: an evolutionary perspective on teh superfamily Vombatoidea. Anatomy and Embryology 203:211-223.

Kempster, R. C., B. J. Bancroft, and L. W. Hirst. 2002. Intraorbital anatomy of the koala (Phascolarctos cinereus). Anatomical Record 267:277-287.

Kempster, R. C., and L. W. Hirst. 2002. Bony orbital anatomy of the koala (Phascolarctos cinereus). Anatomical Record 267:288-291.

Kratzing, J. E. 1984. The anatomy and histology of the nasal cavity of the koala (Phascolarctos cinereus). Journal of Anatomy 138:55-65.

Lanyan, J. M., and G. D. Sanson. 1986. Koala (Phascolarctos cinereus) dentition and nutrition. I. Morphology and occlusion of cheekteeth. Journal of Zoology 209:155-168.

Logan, M., and G. D. Sanson. 2002. The association of tooth wear with sociality of free-ranging male koalas (Phascolarctos cinereus Goldfuss). Australian Journal of Zoology 50:621-626.

Logan, M., and G. D. Sanson. 2002. The effects of tooth wear on the activity patterns of free-ranging koalas (Phascolarctos cinereus Goldfuss). Australian Journal of Zoology 50:281-292.

Moore, B. D., and W. J. Foley. 2000. A review of feeding and diet selection in koalas (Phascolarctos cinereus). Australian Journal of Zoology 48:317-333.

Nowak, R. M. 1999. Walker's Mammals of the World, Sixth Edition. Johns Hopkins University Press, Baltimore, Maryland.

Sullivan, B. J., G. S. Baxter, and A. T. Lisle. 2003. Low-density koala (Phascolarctos cinereus) populations in the mulgalands of southwest Queensland. III. Broad-scale patterns of habitat use. Wildlife Research 30:583-591.

Young, W. G., M. McGowan, and T. J. Daley. 1987. Tooth enamel structure in the koala, Phascolarctos cinereus, some functional interpretations. Scanning Microscopy 1:1925-1934.

Young, W. G., and S. K. Robson. 1987. Jaw movements from microwear on the molar teeth of the koala, Phascolarctos cinereus. Journal of Zoology 213:51-61.

Links

Images of Phascolarctos cinereus at CalPhotos.

Phascolarctos cinereus on the Animcal Diversity Web (Univ. of Michigan Museum of Zoology).

Click on the thumbnail to the left for a pitch animation (1.6 mb) of the isolated Phascolarctos cranial endocast.

Click on the thumbnail to the left for a roll animation (1.6 mb) of the Phascolarctos cranial endocast highlighted in red within the skull, which is rendered semi-transparent.

Click on the thumbnail to the left for a roll animation (1.0 mb) of the isolated Phascolarctos cranial endocast.