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KANGAROO
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KANGAROO , the universally accepted, though not apparently the native, designation of the more typical representatives of the marsupial See also:family Macropodidae (see MARSUPIA1.1A). Although intimately connected with. the cuscuses and phalangers by means of the See also:musk-kangaroo, the kangaroos and wallabies, together with the See also:rat-kangaroos, are easily distinguishable from other diprotodont marsupials by their See also:general conformation, and by peculiarities in the structure of their limbs, See also:teeth and other See also:organs. They vary in See also:size from that of a See also:sheep to a small See also:rabbit. The See also:head, especially in the larger See also:species, is small, compared with the See also:rest of the See also:body, and tapers forward to the muzzle. The shoulders and fore-limbs are feebly See also:developed, and the See also:hind-limbs of disproportionate strength and magnitude, which give the animals a peculiarly awkward See also:appearance when moving about on all-fours; as they occasionally do when feeding. Rapid progression is, however, performed only by the powerful hind-limbs, the animals covering the ground by a See also:series of immense See also:bounds, during which the fore See also:part of the body is inclined forwards, and balanced by the See also:long, strong and tapering tail, which is carried horizontally backwards. When not moving, they often assume a perfectly upright position, the tail aiding the two hind-legs to See also:form a See also:tripod, and the front-limbs dangling by the See also:side of the See also:chest. This position gives full See also:scope for the senses of sight, See also:hearing and See also:smell to warn of the approach of enemies. The fore-paws have five digits, each armed with a strong,' curved claw. The hind-See also:foot is extremely long, narrow and (except in the musk-kangaroo) without the first toe. It consists mainly of one very large and strong toe, corresponding to the See also:fourth of the human foot,' ending in a strong curved and pointed claw (fig. 2). See also:Close to the See also:outer side of this lies a smaller fifth See also:digit, and to the inner side two excessively slender toes (the second and third), See also:bound together almost to the extremity in a See also:common and the See also:radius and ulna are well developed, allowing of considerable freedom of See also:motion of the fore-paw. The See also:pelvis has large epipubic or " marsupial " bones. The femur is See also:short, and the See also:tibia and fibula of See also:great length, as is the foot, the whole of which is applied to the ground when the See also:animal is at rest in the upright position. The See also:stomach is large and very complex, its walls being puckered by See also:longitudinal See also:muscular bands into a number of folds. The alimentary See also:canal is long, and the caecum well developed. The See also:young (which, as in other marsupials, leave the uterus in an extremely small and imperfect See also:condition) are placed in the pouch as soon as they are See also:born; and to this they resort temporarily for shelter for some See also:time after they are able to run, jump and feed upon the herbage which forms the nourishment of the See also:parent. During the See also:early See also:period of their sojourn in the pouch, the See also:blind, naked, helpless young creatures (which in the great kangaroo scarcely exceed an See also:inch in length) are attached by their mouths to the nipple of the See also:mother, and are fed by See also:milk injected into their stomach by the contraction of the muscle covering the mammary gland. In this See also:stage of existence the elongated upper part of the larynx projects into the posterior flares, and so maintains a See also:free communication between the lungs and the See also:external See also:surface, independently of the mouth and gullet, thus averting danger of suffocation while the milk is passing down the gullet. Kangaroos are See also:vegetable-feeders, browsing on ,grass and various kinds of herbage, but the smaller species also eat integument. The two little claws of these toes, projecting together from the skin, may be of use in scratching and cleaning the See also:fur of the animal, but the toes must have quite lost all connexion with the functions of support or progression. This type of foot-structure is termed syndactylous. The dental See also:formula, when completely de- veloped, is incisors ?, canines premolars , molars on each side, giving a See also:total of 34 teeth. The three incisors of the upper See also:jaw are arranged in a continuous arched series, and have crowns with broad cutting edges; the first or See also:middle incisor is often larger than the others. Corresponding to these in the See also:lower jaw is but one tooth on each side, which is of great size, directed horizontally forwards, narrow, lanceolate and pointed with See also:sharp edges. Owing to the slight See also:union of the two halves of the lower jaw in front in many species the two lower incisors See also:work together like the See also:blades of a pair of See also:scissors. The canines are absent or rudimentary in the lower, and often See also:deciduous at an early See also:age in the upper jaw. The first two premolars are compressed, with cutting longitudinal edges, the anterior one is deciduous, being lost about the time the second one replaces the milk-molar, so that three premolars are never found in See also:place and use in the same individual. The last premolar and the molars have quadrate crowns, provided with two strong transverse ridges, or with four obtuse cusps. In Macropus giganteus and its immediate See also:allies, the premolars and sometimes the first molar are See also:shed, so that in old examples only the two posterior molars and the incisors FIG. 2.-See also:Skeleton are found in place. The milk-dentition, as of right hind- in other marsupials, is confined to a single foot of Kan- garoo. tooth on each side of each jaw, the other molars and incisors being never changed. The dentition of the kangaroos, functionally considered, thus consists of sharp-edged incisors, most developed near the median See also:line of the mouth, for the purpose of cropping herbage, and ridged or tuberculated molars for crushing. The number of vertebrae is—in the cervical region 7, dorsal 13, lumbar 6, sacral 2, caudal varying according to the length of the tail, but generally from 21 to 25. In the fore-See also:limb the clavicle Pm m2 3ms roots. They are naturally timid and inoffensive, but the larger kinds when hard pressed will turn and defend themselves, sometimes killing a See also:dog by grasping it in their fore-paws, and inflicting terrible wounds with the sharp claws of their powerful hind-legs, supporting themselves meanwhile upon the tail. The See also:majority are inhabitants of See also:Australia and See also:Tasmania, forming one of the most prominent and characteristic features of the See also:fauna of these lands, and performing the part of the See also:deer and antelopes of other parts of the See also:world. They were important See also:sources of See also:food-See also:supply to the natives, and are hunted by the colonists, both for See also:sport and on See also:account of the damage they do in consuming grass required for See also:cattle and sheep. A few species are found in New See also:Guinea, and the adjacent islands, which belong, in the zoological sense, to the Australian See also:province, beyond the bounds of which none occurs. The more typical representatives of the See also: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 See also: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 Jong 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 See also: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 See also:grey kangaroo (M. giganteus, fig. i) deserves See also:special mention on account of having been discovered during See also:Captain See also:Cook's first voyage in 1770. The great red kangaroo (M. See also:rufus) is about the same size, while other large species are M. antilopinus and M. robustus. The larger wallabies, or See also:brush-kangaroos, such as the red-necked See also:wallaby (M. ruficollis) constitute a group of smaller-sized species; while the smaller wallabies, such as the See also:filander (q.v.) (M. muelleri) and M. thetidis, constitute yet another section. The genus ranges from the eastern Austro-See also:Malay islands to New Guinea. Nearly allied are the See also:rock-wallabies of Australia and Tasmania, constituting the genus Petrogale, chiefly distinguished by the thinner tail being more densely haired and terminating in a See also:tuff. Well-known species are P. penicillata, P. xanthopus and P. lateralis. The few species of See also:nail-tailed wallabies, Onychogale, which are confined to the Australian mainland, take their name from the presence of a horny See also: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 See also:hare-wallabies, such as Lagorchestes leporaides, L. hirsutus and L. consepicillatus, constitute a genus with the same See also: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 See also:swift runners, mostly frequenting open stony plains. 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 Pte' } MI 4'3 MJ i Fig. 4.-See also: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. 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 See also:tree-kangaroos, which include the Papuan Dendrolagus inustus, D. See also:ursinus, D. dorianus, D. benetianus and D. See also:maximus, and the See also:North See also: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 See also:hair on the neck, but the muzzle is only partially hairy, and the See also: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 See also: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, See also:blunt and slightly curved, and the first two premolars of both jaws have large, See also:simple, compressed crowns, with a nearly straight or slightly See also:concave free cutting-edge, and both outer and inner surfaces usually marked by a series of parallel, See also:vertical grooves and ridges. Molars with quadrate crowns and a blunt conical See also:cusp at each corner, the last notably smaller than the rest, sometimes rudimentary or absent. Fore-feet 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 some-times partially prehensile when it is used for carrying bundles ofgrass 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 See also:palate. The See also:tarsus is short and the muzzle naked. The genus includes P. tridactylus, P. gilberti and P. platyops. In Bettongia, on the other See also: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 See also:South Australian Caloprymnus campestris represents a genus near akin to the last, but with the edge of the hairy border of the See also:bare muzzle less emarginate in the middle line, still more swollen auditory bullae, very large and posterially See also:expanded nasals and longer vacuities on the palate. The See also:list is completed by Aepyprymnus rufescens, which differs from all the others by the hairy muzzle, and the See also: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-See also: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. (W. H. F.; R. L.*) KANGAROO-RAT, a name applied in different parts of the world to two widely different See also:groups of mammals. In Australia it is used to denote the small kangaroo-like marsupials technically known as Potoroinae, which zoologists prefer to See also:call rat-kangaroos (see See also:MARSUPIALIA and KANGAROO). In North See also:America it is employed for certain small See also:jumping rat-like rodents nearly allied to the See also:pocket-gophers and belonging to the family Geomyidae. Kangaroo-rats in this latter series are represented by three North See also:American genera, of which Dipodomys phillipsi, Cricetodipus agilis and Microdipodops megacephalus may respectively be taken as examples. Resembling pocket-gophers in the See also:possession of cheek-pouches, kangaroo-rats, together with pocket-mice, are distinguished by their elongated hind-limbs and tails, large eyes, well-developed ears and general See also:jerboa-like appearance and habits. The upper incisor teeth are also relatively narrower, and there are important See also:differences in the skull. The cheek-teeth are rootless in kangaroo-rats, but they develop roots in the pocket-mice. The former inhabit open, sandy districts, where they burrow beneath rocks or stones, and See also:hop about like jerboas; their food consisting of See also:grasses and other See also:plants. Additional information and CommentsThere are no comments yet for this article.
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