This page serves supplemental imagery for a paper entitled Comparative finite element analysis of the cranial performance of four herbivorous marsupials by A.C. Sharp (In press, Journal of Morphology). The abstract is as follows:

Marsupial herbivores exhibit a wide variety of skull shapes and sizes to exploit different ecological niches. Several studies on teeth, dentaries, and jaw adductor muscles indicate that marsupial herbivores exhibit different specializations for grazing and browsing. No studies, however, have examined the skulls of marsupial herbivores to determine the relationship between stress and strain, and the evolution of skull shape. The relationship between skull morphology, biomechanical performance, and diet was tested by applying the finite element method to the skulls of four marsupial herbivores: the common wombat (Vombatus ursinus), koala (Phascolarctos cinereus), swamp wallaby (Wallabia bicolor), and red kangaroo (Macropus rufus). It was hypothesized that grazers, requiring stronger skulls to process tougher food, would have higher biomechanical performance than browsers. This was true when comparing the koala and wallaby (browsers) to the wombat (a grazer). The cranial model of the wombat resulted in low stress and high mechanical efficiency in relation to a robust skull capable of generating high bite forces. However, the kangaroo, also a grazer, has evolved a very different strategy to process tough food. The cranium is much more gracile and has higher stress and lower mechanical efficiency, but they adopt a different method of processing food by having a curved tooth row to concentrate force in a smaller area and molar progression to remove worn teeth from the tooth row. Therefore, the position of the bite is crucial for the structural performance of the kangaroo skull, while it is not for the wombat which process food along the entire tooth row. In accordance with previous studies, the results from this study show the mammalian skull is optimized to resist forces generated during feeding. However, other factors, including the lifestyle of the animal and its environment, also affect selection for skull morphology to meet multiple functional demands.

Click here to download the original DICOM dataset (177 Mb).

This specimen, whose sex is unknown, was collected in Balranald, New South Wales, Australia on 23 August 1962. It was made available to DigiMorph.org by Dr. Alana Sharp of the University of New England.

The skull and mandible were scanned separately at St. Vincent's Public Hospital in Melbourne, Australia, by Shelley O'Hara and Alana Sharp, using a Siemens Sensation 64 scanner. The mandible was scanned along the coronal axis for a total of 591 slices, with an interslice spacing of 0.30 mm and an interpixel spacing of 0.25 mm.

Click here to download the original DICOM dataset (177 Mb).

Literature

Sharp, A. In press. Comparative finite element analysis of the cranial performance of four herbivorous marsupials. Journal of Morphology.

Links

Macropus rufus page on Wikipedia

M. rufus page on the Animal Diversity Web (University of Michigan Museum of Zoology)

None available.