The order Dasyuromorphia comprises the Australian radiation of the polyprotodont marsupials and is restricted to Australia, New Guinea, Tasmania, and some smaller close-by islands. At times during evolutionary history, including most recently the Pleistocene (2 million to 10,000 years ago), land bridges connected Australia and New Guinea, and Australia and Tasmania, and there was opportunity for interchange between the faunas of these major land masses. This historical pattern of connectivity between land masses is reflected in the distributions and genetic relationships of species. Two species of dasyurids in the genus Sminthopsis—S. archeri and S. vir-giniae—have ranges that cross Torres Strait from northern Australia to New Guinea, and one of the New Guinean quolls, the bronze quoll (Dasyurus spartacus), is very closely related to the chuditch (D. geoffroii) from the Australian mainland. All of the Tasmanian dasyurid species are currently, historically, or prehistorically (depending on the timing of mainland extinctions) represented in mainland populations (seven species). Where genetic studies have been carried out, mainland and Tasmanian populations represent different evolutionary significant units, a consequence of over 10,000 years of evolutionary separation. It is notable, however, that these faunal interchanges were restricted largely to savanna and woodland species. The cold, dry conditions that prevailed during the Pleistocene precluded the development of significant rainforest corridors. Rainforest Antechinus of Cape York and the sister clade Murexia from New Guinea did not make it across the land bridge, although some small dasyurids of wet habitats (Antechinus minimus—closed, wet heath, grass or sedgelands; A. swainsonii—wet forest and heath) do occur on either side of Bass Strait.

A spotted-tailed quoll (Dasyurus maculatus) gets a drink in eastern Australia. (Photo by E. & P. Bauer. Bruce Coleman, Inc. Reproduced by permission.)

at the expense of the carnassial cusps (sharp, pointy bits) and the molar teeth become wider and more triangular in shape. A feature at least of the larger dasyuromorphians is continual or over-eruption of the canine teeth throughout life. This may be a consequence, again, of early eruption of the permanent teeth at an age when the juvenile animal is less than half of its adult size. Over-eruption, while probably a response to tooth wear and occlusal patterns, has the effect that the canine teeth continue to get bigger as the individual grows.

Coat color in most species ranges from sandy to reddish to grayish brown, sometimes with a lighter colored underbelly. Black is rare (only devils and one of the two color phases of the eastern quoll) and only eight taxa have distinct markings: stripes on the back in the thylacine, numbat and three groups of New Guinean dasyurids, a facial stripe in the num-bat, spots in the quolls and white chest, shoulder and rump markings in the devil. Fur length is mostly short to slightly wispy, although tail fur can vary from short, to a bushy tip, to completely fluffy or bushy.

0 0

Post a comment