On the Australian side the fact that Tasmania is richest in marsupial types indicates the gate by which they entered.
The marsupial tiger or Tasmanian wolf (Thylacinus cynocephalus), 5 ft.
With the exception of this replacing pair of teeth in each jaw, it is considered by many authorities that the marsupial dentition corresponds to the deciduous, or milk, dentition of placentals.
- The Marsupial or Banded Ant-eater (Myrmecobius fasciatus).
Molar teeth of the simple tritubercular type persist in the golden moles (Chrysochloris) among the Insectivora and also in the marsupial mole (Notoryctes) among the marsupials.
It may be added that there are some marsupials, such as the wombat, koala, marsupial ant-eater and the dasyures, FIG.
On the other hand, it is noteworthy that this marsupial retains in its lower jaw the so-called mylo-hyoid groove, which is found in the aforesaid Jurassic mammals.
There seems to have been a replacement of some of these teeth; and it has been suggested that this was of the marsupial type.
An interesting link between divergent marsupial families, still living in Ecuador, the Coenolestes, is another discovery of recent years.
KOALA (Phascolarctus cinereus), a stoutly built marsupial, of the family Phascolmyidae, which also contains the wombats.
One of these, Prothylacinus, is regarded as the forerunner of the marsupial wolf of Tasmania.
BANDICOOT, any animal of the marsupial genus Perameles, which is the type of a family Peramelidae.
MARSUPIAL MOLE (Notoryctes typhlops), the "Ur-quamata" of the natives, an aberrant polyprotodont from central South Australia, constituting a family (Notoryctidae).
Owing to the deep water between Timor and the Arafura Sea, the fauna of Timor presents scarcely any Australian types beyond a marsupial cuscus.
It may be added that the formula given above shows that the marsupial dentition may comprise more teeth than the 44 which form the normal full placental complement.
Except the opossums, no single living marsupial is known outside the Australian zoological region.
This is Tasmania, where as in the adjacent continent of Australia, the survival of marsupial animals indicates long isolation from the rest of the world.
The most remarkable feature about the marsupial dentition is that, at most, only a single pair of teeth is replaced in each jaw; this pair, on the assumption that there are four premolars, representing the third of that series.
That is to say, he believes that, with the exception of the duckbill and the echidna, the mammalian class as a whole can lay claim to descent from small arboreal forms. This view is, of course, almost entirely based upon palaeontological considerations; and these, in the author's opinion, admit of the conclusion that all modern placental and marsupial mammals are descended from a common ancestral stock, of which the members were small in bodily size.
Marsupials may be defined as viviparous (that is non-egglaying) mammals, in which the young are born in an imperfect condition, and almost immediately attached to the teats of the mammary glands; the latter being generally enclosed in a pouch, and the front edge of the pelvis being always furnished with epipubic or "marsupial" bones.
From all other members of the family the marsupial, or banded, ant-eater (Myrmecobius fasciatus) differs by the presence of more than seven pairs of cheek-teeth in each jaw, as well as by the exceedingly long and protrusile tongue.
A separate family, Notoryctidae, is represented by the marsupial mole (Notoryctes typhlops), of the deserts of south Central Australia, a silky, golden-haired, burrowing creature, with a curious leathery muzzle, and a short, naked stumpy tail.
Spencer, "Mammalia of the Horn Expedition" (1896); "Wynyardia, a Fossil Marsupial from Tasmania," Proc. Zool.