Evolution and systematics

This small family of just two living species has created more than its share of taxonomic debate. Feather-tailed possums were once thought to be true possums of the family Pha-langeridae. In the 1970s, they were moved to the pygmy possum family, Burramyidae. Soon after that, they were given full family status of their own and became the Acrobatidae, allied first to the pygmy possums in the superfamily Bur-ramyoidea, then with gliding possums in the Petauroidea. In 1987, the family was repositioned again, this time alongside the honey possum in the superfamily Tarsipedoidea.

Acrobatids differ from other possums in having six pads on their feet instead of five (an adaptation to enhance grip when climbing) and a tail with rows of long stiff hairs along each side, forming a feather-like structure. Undoubtedly, this is an adaptation to gliding. In the Australian pygmy glider (Acrobates pygmaeus), the tail is used as a rudder to give the animal increased control as it glides though the air on membranes of skin stretched between its front and back legs. But the other species, New Guinea's feather-tailed possum (Distoechurus pennatus), does not have such a membrane and cannot glide.

The tail of the pygmy glider (Acrobates pygmaeus) is its most notable characteristic. (Photo by Pavel German. Reproduced by permission.)

The featherlike tail is a relic that shows that this species has abandoned the gliding lifestyle its ancestors spent several million years evolving.

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