The Geographical Distribution of Animals/Chapter 17.2

The Didelphyidæ, or true opossums, range throughout all the wooded districts of the Neotropical region from the southern boundary of Texas to the River La Plata, and on the west coast to 42° S. Lat., where a species of Didelphys was obtained by Professor Cunningham. One species only is found in the Nearctic region, extending from Florida to the Hudson River, and west to the Missouri. The species named Didelphys californica inhabits Mexico, and only extends into the southern extremity of California. The species are most numerous in the great forest region of Brazil, and they have been recently found to the west of the Andes near Guayaquil, as well as in Chili. The exact number of species is very doubtful, owing to the difficulty of determining them from dried skins. All but two belong to the genus Didelphys, which has the range above given for the family (Plate XIV., vol. ii. p. 24); Chironectes (1 sp.), the yapock or water opossum, inhabits Guiana and Brazil; Hyracodon (1 sp.), is a small rat-like animal discovered by Mr. Fraser in Ecuador, and which may perhaps belong to another family.

Extinct Didelphyidæ.—No less than seven species of Didelphys have been found in the caves of Brazil, but none in the older formations. In North America the living species only, has been found in Post-Pliocene deposits. In Europe, however, many species of small opossums, now classed as a distinct genus, Peratherium, have been found in various Tertiary deposits from the Upper Miocene to the Upper Eocene.

We have here a sufficient proof that the American Marsupials have nothing to do with those of Australia, but were derived from Europe, where their ancestors lived during a long series of ages.

The Dasyuridæ, or native cats, are a group of carnivorous or insectivorous marsupials, ranging from the size of a wolf to that of a mouse. They are found all over Australia and Tasmania, as well as in New Guinea and the adjacent Papuan islands. Several new genera and species have recently been described by Mr. G. Krefft, of the Sydney Museum, and are included in the following enumeration. Phascogale (3 sp.), New Guinea, West, East, and South Australia; Antechinomys (1 sp.), Interior of South Australia; Antechinus (12 sp.), Aru Islands, all Australia, and Tasmania; Chætocercus (1 sp.), South Australia; Dactylopsila (1 sp.), Aru Islands and North Australia; Podabrus (5 sp.), West, East, and South Australia, and Tasmania; Myoictis (1 sp.), Aru Islands; Sarcophilus (1 sp.), Tasmania; Dasyurus (4 sp.), North, East, and South, Australia, and Tasmania; Thylacinus (1 sp.), Tasmania (Plate XI., vol. i. p. 439).

Extinct species of Dasyurus and Thylacinus have been found in the Post-Pliocene deposits of Australia.

The only representative of this family is the Myrmecobius fasciatus, or native ant-eater, a small bushy-tailed squirrel-like animal, found in the South and West of Australia.

The Peramelidæ, or bandicoots, are small insectivorous Marsupials, having something of the form of the kangaroos. They range over the whole of Australia and Tasmania, as well as the Papuan Islands. The genus Perameles (8 sp.), has the range of the family, one species being found in New Guinea and the Aru Islands (Plate XI., vol. i. p. 440); Peragalea (1 sp.), inhabits West Australia only; and Chœropus (1 sp.), a beautiful little animal with something of the appearance of a mouse-deer, is found in both South, East, and West Australia.

The well-known Kangaroos are the most largely developed family of Marsupials, and they appear to be the form best adapted for the present conditions of life in Australia, over every part of which they range. One genus of true terrestrial kangaroos (Dorcopsis), inhabits the Papuan Islands, as do also the curious tree kangaroos (Dendrolagus) which, without much apparent modification of form, are able to climb trees and feed upon the foliage. The genera, as established by Mr. Waterhouse, are as follows: Macropus (4 sp.), West, South, and East Australia, and Tasmania (Plate XII., vol. i. p. 441); Osphranter (5 sp.), all Australia; Halmaturus (18 sp.), all Australia and Tasmania; Petrogale (7 sp.), all Australia; Dendrolagus (2 sp.), New Guinea (Plate X., vol. i. p. 414); Dorcopsis (2 sp.) Aru and Mysol Islands, and New Guinea; Onychogalea (3 sp.), Central Australia; Lagorchestes (5 sp.), North, West, and South Australia; Bettongia (6 sp.), West, South, and East, Australia, and Tasmania; Hypsiprymnus (4 sp.), West and East Australia, and Tasmania.

Extinct Macropodidæ.—Many species of the genera Macropus and Hypsiprymnus have been found in the cave-deposits and other Post-Tertiary strata of Australia. Among the extinct genera are Protemnodon and Sthenurus, which are more allied to the tree-kangaroos of New Guinea than to living Australian species; the gigantic Diprotodon, a kangaroo nearly as large as an elephant; and Nototherium, of smaller size.

The Phalangistidæ, or phalangers, are one of the most varied and interesting groups of Marsupials, being modified in a variety of ways for an arboreal life. We have the clumsy-looking tail-less koala, or native sloth; the prehensile-tailed opossum-like phalangers; the beautiful flying oppossums, so closely resembling in form the flying squirrels of North America and India, but often no larger than a mouse; the beautiful dormouse-like Dromiciæ, one species of which is only 2¼ inches long or less than the harvest-mouse; and the little Tarsipes, a true honey-sucker with an extensile tongue, and of the size of a mouse. These extreme modifications and specializations within the range of a single family, are sufficient to indicate the great antiquity of the Australian fauna; and they render it almost certain that the region it occupied was once much more extensive, so as to supply the variety of conditions and the struggle between competing forms of life, which would be required to develop so many curiously modified forms, of which we now probably see only a remnant.

The Phalangistidæ not only range over all Australia and Tasmania, but over the whole of the Austro-Malayan sub-region from New Guinea to the Moluccas and Celebes. The distribution of the genera is as follows:—Phascolarctos (1 sp.), the koala, East Australia; Phalangista (5 sp.), East, South, and West Australia, and Tasmania; Cuscus (8 sp.), woolly phalangers, New Guinea, North Australia, Timor, Moluccas and Celebes; Petaurista (1 sp.) large flying phalanger, East Australia; Belideus (5 sp.), flying opossums, South, East, and North Australia, New Guiana and Moluccas; Acrobata (1 sp.), pigmy flying opossum, South and East Australia; Dromicia (5 sp.), dormouse-phalangers, West and East Australia, and Tasmania; Tarsipes (1 sp.), West Australia.

Thylacoleo, a large extinct marsupial of doubtful affinities, seems to be somewhat intermediate between this family and the kangaroos. Professor Owen considered it to be carnivorous, and able to prey upon the huge Diprotodon, while Professor Flower and Mr. Gerard Krefft, believe that it was herbivorous.

The Wombats are tail-less, terrestrial, burrowing animals, about the size of a badger, but feeding on roots and grass. They inhabit South Australia and Tasmania (Plate XI. vol. i. p. 439).

An extinct wombat, as large as a tapir, has been found in the Australian Pliocene deposits.

We have here the most remarkable case, of an extensive and highly varied order being confined to one very limited area on the earth's surface, the only exception being the opossums in America. It has been already shown that these are comparatively recent immigrants, which have survived in that country long after they disappeared in Europe. As, however, no other form but that of the Didelphyidæ occurs there during the Tertiary period, we must suppose that it was at a far more remote epoch that the ancestral forms of all the other Marsupials entered Australia; and the curious little mammals of the Oolite and Trias, offer valuable indications as to the time when this really took place.

A notice of these extinct marsupials of the secondary period will be found at vol. i. p. 159.

The Ornithorhynchus, or duck-billed Platypus, one of the most remarkable and isolated of existing mammalia, is found in East and South Australia, and Tasmania.

The Echidna, or Australian Hedgehog, although quite as remarkable in internal structure as the Ornithorhynchus, is not so peculiar in external appearance, having very much the aspect of a hedgehog or spiny armadillo. The two species of this genus are very closely allied; one inhabits East and South Australia, the other Tasmania.

Extinct Echidnidæ.—Remains of a very large fossil species of Echidna have lately (1868) been discovered at Darling Downs in Australia.

This order is the lowest and most anomalous of the mammalia, and nothing resembling it has been found among the very numerous extinct animals discovered in any other part of the world than Australia.