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MARSUPIALIA

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Originally appearing in Volume V21, Page 345 of the 1911 Encyclopedia Britannica.
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MARSUPIALIA. The most generalized representatives of the group appear to be the ring-tailed phalangers, constituting the genus Pseudochirus, which is common to Australia, Tasmania and New Guinea, and includes at least half a score of species. The dentition is generally i. , c. j, p.+m. i, but one upper incisor and the canine may be wanting. The crowns of the molars show a crescenticutructure, but they are said to retain the three primitive cusps, which are fused in the other genera. The prehensile tail has its tip naked for a short distance, and the whole of the terminal third and the under surface of the remainder short-haired, the tip being generally white. The hair is thick and woolly, and generally yellowish-olive in colour. These phalangers are the ring-tailed opossums of the Australians. From this genus is apparently derived the taguan flying-squirrel, or flying-phalanger (Petauroides volans), which ranges from Queensland to Victoria, and is the largest of the flying group. Its dentition is essentially similar to that of Pseudochirus, although there is one pair less of cheek-teeth, and the bushy tail is naked and prehensile at the tip. Reverting to the non-flying species, we have Gymnobelideus leadbeateri, a small animal from Victoria representing a genus by itself, with the same dental formula as Pseudochirus, but cheek-teeth of a different type, the ears naked (instead of hairy) behind, glands on the chest and between the ears, and the tail long and evenly bushy to the tip. From this are evidently derived the flying-phalangers—flying-squirrels—of the genus Petaurus, which differ merely in the possession of a parachute, and are represented by several species, ranging from Australia (exclusive of Tasmania) to the Aru Islands, New Guinea, and New Ireland. Of the yellow-bellied species, P. australis, the habits are described by J. Gould as follows: " This animal is common in all the brushes of New South Wales, particularly those which stretch along the coast from Port Philip to Moreton Bay. In these vast forests trees of one kind or another are perpetually flowering, and thus offer a never-failing supply of the blossoms upon which it feeds; the flowers of the various kinds of gums, some of which are of great magnitude, are the principal favourites. Like the rest of the genus, it is nocturnal in its habits, dwelling in holes and in the spouts of the larger branches during the day, and displaying the greatest activity at night while running over the small leafy branches, frequently even to their very extremities, in search of insects and the honey of the newly opened blossoms. Its structure being ill adapted for terrestrial habits, it seldom descends to the ground except for the purpose of passing to a tree too distant to be attained by springing from the one it wishes to leave. The tops of the trees are traversed by this animal with as much ease as the most level ground is by such as are destined for terra firma. If chased or forced to flight it ascends to the highest branch and performs the most enormous leaps, sweeping from tree to tree with wonderful address; a slight elevation gives its body an impetus which with the expansion of its membrane enables it to pass to a considerable distance, always ascending a little at the extremity of the leap; by this ascent the animal is prevented from receiving the shock which it would otherwise sustain." A second species, P. sciureus, in some ways one of the most beautiful of all mammals, is shown in fig. 2. A precisely similar relationship exists between the tiny feather-tailed phalanger, Distoechurus pennatus, of New Guinea, and the equally minute pigmy flying-phalanger or flying-mouse, Acrobates pygmaeus, of Queensland, New South Wales and Victoria; both being characterized by the hairs of the tail forming a vane on each side, as well as by tufts of long hairs at the base of the thinly-haired ears. There are six pairs of cheek-teeth, of which the last three are small and rounded, with blunted cusps, while the anterior teeth are sharp and of insectivorous type. The pigmy flyingphalanger feeds on honey from flowers and insects. To some extent intermediate in structure between Acrobates and Petaurus, although without a parachute, are the beautiful little dormouse-phalangers, as typifed by Dromicia nana, which range from Western Australia and Tasmania to New Guinea. They appear to be a generalized type, which has died out where they have come into competition with the more specialized forms. Although unable to fly they are exceedingly active, and take long leaps from bough to bough; externally they are characterized by their dormouse- like form, large, thin, and nearly naked ears, without tufts inside or at the base, sharp and rudimentary front claws and long sharp hind ones, and mouse-like tail, which is furry at the base, then scaly, and naked and prehensile at the tip. There may be either six or seven pairs of cheek-teeth, of which the hinder carry four small smooth cusps, and the first upper incisor is much longer than the other two. The striped phalangers (Dactylopsila) are larger animals, of the approximate size of a squirrel, easily recognized by the longitudinal yellow and black striping of the fur, and the slender and elongated fourth front toe. The typical D. trivirgata is common to north Australia and New Guinea, but D. palpator, which has the fourth toe still more elongated, is exclusively Papuan. They have seven pairs of cheek-teeth, of which the four last are oblong and four-cusped; and the first lower incisor is longer than in any other phalanger. They apparently feed on both leaves and grubs, probably extracting the latter from crannies with the elongated toe. The tail is more or less bare on the under side of the tiThe last group of the sub-family is represented firstly by the cuscuses, or cususes (Phalanger), which are arboreal animals of the approximate size of cats, and range from the Solomon Islands through New Guinea and the Moluccas to Celebes, being, in fact, the only Old World marsupials found westwards of New Guinea. Externally they are characterized by their thick woolly fur, short or medium ears, which are hairy outside, and sometimes inside as well, by the naked and striated soles of the feet, and the long and markedly prehensile tail, of which the basal half is furred like the body, and the terminal half entirely naked. The number of cheek-teeth varies, owing to the frequent absence of some of the front ones, but there are generally seven pairs, of which the last four carry crescents internally and cusps externally. About ten species are known, of which the grey cuscus (P. orientalis) of Amboyna and Timor was discovered about 300 years ago, and was thus the first known Old World marsupial. In the spotted cuscus (P. maculatus) the males are marked with orange and white, while the females are uniformly greyish. Cuscuses are sleepy animals, feeding mainly on leaves, but also devouring birds and small mammals. Nearly allied to the cuscuses are the typical Australian phalangers, or opossums, forming the genus Trichosurus. They differ from the cuscuses, among other features, by the thick and non-tapering tail being covered with bushy hair up to the extreme tip, which is naked, as is a narrow line along the middle of the terminal third (or rather more) of the lower surface, by the presence of a gland on the chest, and by the soles of the hind feet being hairy. In the skull the upper canine is separated from the outermost incisor, instead of close to it as in the cuscuses (fig. I). The best-known species is the brush-tailed phalanger, or brush-tailed opossum (T. vulpecula), of Australia, an animal of the size of a small fox, represented in Tasmania by the brown phalanger (T. vulpecula fuliginosus). The short-eared phalanger (T. caning) represents the group in Southern Queensland and New South Wales. The dental formula in both is J. I, c. p. , m. I. These animals are wholly arboreal and mainly nocturnal in their habits; and it is these which form the chief game in " opossum-shooting " among the gum-trees by moonlight. The long-snouted phalanger is referred to under MARSUr1ALTA. (R. L.*)
End of Article: MARSUPIALIA
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