Petaurus breviceps (Waterhouse 1839; Early Miocene to present; up to 30cm) is the extant sugar glider, a nocturnal squirrel-like marsupial able to climb trees and glide with furry membranes between the fore and hind limbs. An opposable toe is present on each hind foot. Sharp claws tip every digit. This taxon is an omnivore closely related to Thylacoleo, the marsupial lion (below).

Wakaleo vanderleuri (Clemens and Plane 1974; Miocene) is a transitional taxon between the tiny sugar glider Petaurus and the much larager Thylacoleo. Three molars are retained.

Thylacoleo carnifex (Owen 1859; Pliocene-Pleistocene; 1.14 m long) was a giant sugar glider derived from Petaurus and Wakaleo. Thylacoleo had the strongest bite of any mammal with the largest, sharpest premolars of any mammal. The molars were absent. The canine is tiny. Thylacoleo had fewer but larger teeth than Petaurus. The manus included retractable claws. The pes had a very large heel bone (calcaneum). This supposedly carnivorous 'marsupial lion' nests with equally slow-moving herbivores. Pedal digit 1 likely had a phalanx and claw, but it has not been shown.

Sugar gliders strip bark off of trees and the very odd teeth of Thylacoleo could have done the same on a larger scale.

Owen R 1859. On the fossil mammals of Australia. Part II. Description of a mutilated skull of the large marsupial carnivore (Thylacoleo carnifex Owen), from a calcareous conglomerate stratum, eighty miles S. W. of Melbourne, Victoria. Philosophical Transactions of the Royal Society 149, 309-322.

Waterhouse GR 1838. Observations on certain modifications observed in the dentition of the Flying Opossums (the genus Petaurus of authors). Proceedings of the Zoological Society of London. 4: 149–153.

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wiki/Wakaleo
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