Kangaroo

The more typical representatives of the group constitute the sub-family Macropodinae, in which the cutting-edges of the upper incisors are nearly level, or the first pair but slightly longer than the others (fig. 3). The canines are rudimentary and often wanting. The molars are usually not longer (from before backwards) than the anterior premolars, and less compressed than in the next section. The crowns of the molars have two prominent transverse ridges. The fore-limbs are small with subequal toes, armed with strong, moderately long, curved claws. Hind-limbs very long and strongly made. Head small, with more or less elongated muzzle. Ears generally rather long and ovate.

The typical genus Macropus, in which the muzzle is generally naked, the ears large, the fur on the nape of the neck usually directed backwards, the claw of the fourth hind-toe very large, and the tail stout and tapering, includes a large number of species. Among these, the great grey kangaroo (M. giganteus, fig. 1) deserves special mention on account of having been discovered during Captain Cook’s first voyage in 1770. The great red kangaroo (M. rufus) is about the same size, while other large species are M. antilopinus and M. robustus. The larger wallabies, or brush-kangaroos, such as the red-necked wallaby (M. ruficollis) constitute a group of smaller-sized species; while the smaller wallabies, such as the filander (q.v.) (M. muelleri) and M. thetidis, constitute yet another section. The genus ranges from the eastern Austro-Malay islands to New Guinea.

Nearly allied are the rock-wallabies of Australia and Tasmania, constituting the genus Petrogale, chiefly distinguished by the thinner tail being more densely haired and terminating in a tuff. Well-known species are P. penicillata, P. xanthopus and P. lateralis. The few species of nail-tailed wallabies, Onychogale, which are confined to the Australian mainland, take their name from the presence of a horny spur at the end of the tail, and are further distinguished by the hairy muzzle. O. unguifer, O. fraenatus and O. lunatus represent the group. The hare-wallabies, such as Lagorchestes leporoides, L. hirsutus and L. consepicillatus, constitute a genus with the same distribution as the last, and likewise with a hairy muzzle, but with a rather short, evenly furred tail, devoid of a spur. They are great leapers and swift runners, mostly frequenting open stony plains.

Fig. 4.—Skull and teeth of Lesueuir’s Rat-Kangaroo (Bettongia lesueuiri). c, upper canine. Other letters as in fig. 3. The anterior premolar has been shed.

More distinct is the Papuan genus Dorcopsis, as typified by D. muelleri, although it is to some extent connected with Macropus by D. macleyi. The muzzle is naked, the fur on the nape of the neck directed more or less completely forward, and the hind-limbs are less disproportionately elongated. Perhaps, however, the most distinctive feature of the genus is the great fore-and-aft length of the penultimate premolar in both jaws. Other species are D. rufolateralis and D. aurantiacus. In the tree-kangaroos, which include the Papuan Dendrolagus inustus, D. ursinus, D. dorianus, D. benetianus and D. maximus, and the North Queensland D. lumholtzi, the reduction in the length of the hind-limbs is carried to a still further degree, so that the proportions of the fore and hind limbs are almost normal. The genus agrees with Dorcopsis in the direction of the hair on the neck, but the muzzle is only partially hairy, and the elongation of the penultimate premolar is less. These kangaroos are largely arboreal in their habits, but they descend to the ground to feed. Lastly, we have the banded wallaby, Lagostrophus fasciatus, of Western Australia, a small species characterized by its naked muzzle, the presence of long bristles on the hind-feet which conceal the claws, and also of dark transverse bands on the lower part of the back. The skull has a remarkably narrow and pointed muzzle and much inflated auditory bullae; while the two halves of the lower jaw are firmly welded together at their junction, thus effectually preventing the scissor-like action of the lower incisors distinctive of Macropus and its immediate allies. As regards the teeth, canines are wanting, and the penultimate upper premolar is short, from before backwards, with a distinct ledge on the inner side.

In the rat-kangaroos, or kangaroo-rats, as they are called in Australia, constituting the sub-family Potoroinae, the first upper incisor is narrow, curved, and much exceeds the others in length; the upper canines are persistent, flattened, blunt and slightly curved, and the first two premolars of both jaws have large, simple, compressed crowns, with a nearly straight or slightly concave free cutting-edge, and both outer and inner surfaces usually marked by a series of parallel, vertical grooves and ridges. Molars with quadrate crowns and a blunt conical cusp at each corner, the last notably smaller than the rest, sometimes rudimentary or absent. Forefeet narrow; the three middle toes considerably exceeding the first and fifth in length and their claws long, compressed and but slightly curved. Hind-feet as in Macropus. Tail long, and sometimes partially prehensile when it is used for carrying bundles of grass with which these animals build their nests. The group is confined to Australia and Tasmania, and all the species are relatively small.

In the members of the typical genus Potorous (formerly known as Hypsiprymnus) the head is long and slender, with the auditory bullae somewhat swollen; while the ridges on the first two premolars are few and perpendicular, and there are large vacuities on the palate. The tarsus is short and the muzzle naked. The genus includes P. tridactylus, P. gilberti and P. platyops. In Bettongia, on the other hand, the head is shorter and wider, with smaller and more rounded ears, and more swollen auditory bullae. The ridges on the first two premolars are also more numerous and somewhat oblique (fig. 4); the tarsus is long and the tail is prehensile. The species include B. lesueuiri, B. gaimardi and B. cuniculus. The South Australian Caloprymnus campestris represents a genus near akin to the last, but with the edge of the hairy border of the bare muzzle less emarginate in the middle line, still more swollen auditory bullae, very large and posterially expanded nasals and longer vacuities on the palate. The list is completed by Aepyprymnus rufescens, which differs from all the others by the hairy muzzle, and the absence of inflation in the auditory bullae and of vacuities in the palate.

Perhaps, however, the most interesting member of the whole group is the tiny musk-kangaroo (Hypsiprymnodon moschatus) of north-east Australia, which alone represents the sub-family Hypsiprymnodontinae, characterized by the presence of an opposable first toe on the hind-foot and the outward inclination of the penultimate upper premolar, as well by the small and feeble claws. In all these features the musk-kangaroo connects the Macropodidae with the Phalangeridae. The other teeth are like those of the rat-kangaroos.