Bone Abnormalities in Two Groups of Macropod Skulls: a Clue to the Origin of Lumpy Jaw.

Eighty-one skulls of Macropus giganteus from the Yan Yean collection and 38 from the Greymare collection were examined grossly and radiographically for bony abnormalities; six Yan Yean and two Greymare skulls were diseased. Post-functional molar teeth showed unexpectedly high amounts of alveolar bone loss around the necks of the teeth. Food packing into these, and other interdental defects, was observed. It is believed that this kind of functional defect may represent the early stages of lumpy jaw in those macropods which exhibit molar progression. It is probable that an opportunist oral microorganism can invade the underlying connective tissues via such a break in the oral integument. Two animals, which had osteomyelitis associated with residual gunshot pellets in the dentary, did not have signs of early or late lumpy jaw, but neither did the lesions have contact with the oral cavity, although dental development had been grossly disturbed. Examination of the distribution of mineralized deposits on the teeth (dental calculus) showed them to be heavy even on partly erupted teeth, less so on functional teeth, and again heavy on post-functional teeth. An electron microprobe study of their elemental composition leads us to believe that the dark brown pigmentation of this calculus is due to manganese.