Comparisons of indices of molar progression and dental function of brush-tailed rock-wallabies (Petrogale penicillata) with tammar (Macropus eugenii) and parma (Macropus parma) wallabies

Abstract

We measured parameters of molar progression and dental function in the brush-tailed rock-wallaby (Petrogale pencilliata) (a browser/grazer) and compared them with data from the tammar wallaby (Macropus eugenii) (a grazer) and the parma wallaby (Macropus parma) (a grazer/browser).Although the mean value of the molar index (MI) was higher in rock-wallabies than in parma and tammar wallabies the mean rate of increase of log(MI) with log(body mass) was similar in the three species. Reported differences between these species in their rates of molar progression with age may therefore result from differences in their rates of bodily growth. The findings indicate that molar progression in the rock-wallaby is governed by the growth of the bones of the viscerocranium (mesial shift), rather than by diet-induced movement of the teeth within the bones of the viscerocranium (mesial drift), and was not influenced by the persistence of P4 premolars. It is therefore unlikely that differences in the rate of molar progression are directly linked to differences in diet.The relationship between functional dental parameters and body mass differed between brush-tailed rock-wallabies and tammar wallabies, species of differing dietary habit, but did not differ between brush-tailed rock-wallabies and parma wallabies, species of more similar dietary habit. Thus the total length of upper transverse lophine ridges and the interlophine distances of the M1 to M3 upper molars of brush-tailed rock-wallabies were not different from those of parma wallabies but were significantly greater than those of tammar wallabies. These differences can be interpreted in terms of greater emphasis on crushing/grinding of browse in the rock-wallabies and parma wallabies.