At just in head-and-body length and weighing about , the feathertail glider is only around the size of a small mouse, and is the world's smallest gliding mammal. Like other gliding mammals, the feathertail glider has a
patagium stretching between the fore and hind legs. Only reaching the elbows and knees, this is smaller than that of the
petaurid gliding possums, although the presence of a fringe of long hairs increases its effective area. The tail is about the same length as the head and body combined, oval in cross-section, only slightly prehensile, and has very short fur except for two distinctive rows of long, stiff hairs on either side. This gives the tail the appearance of a feather or a double-sided comb. The hindfeet possess enlarged, opposable
first digits, which unlike all the other toes on both fore and hind feet, lack claws. The structure of the ear is also unusual, since the animal possesses a unique bony disc with a narrow crescent-shaped slit just in front of the
eardrum. The function of this bone is unclear, but it may act as a
Helmholtz resonator and enhance sensitivity to certain frequencies of sound. The brain has been recorded as weighing . The female has two
vaginae, which merge into a single sinus before opening into a
cloaca together with the rectum. The pouch opens towards the front, as is common in
diprotodont marsupials, and contains four teats. ==Distribution and habitat==