Planetetherium is an extinct genus of herbivorous gliding mammal (not unlike Colugo

Colugo

Colugos are arboreal gliding mammals found in South-east Asia. There are just two extant species, which make up the entire family Cynocephalidae and order Dermoptera. They are the most capable of all gliding mammals, using flaps of extra skin between their legs to glide from higher to lower...

) endemic to North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 during the Paleogene

Paleogene

The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...

 living from 56.8—55.4 mya, existing for approximately .

Fossils have been discovered in strata formed from ancient cypress

Cypress

Cypress is the name applied to many plants in the cypress family Cupressaceae, which is a conifer of northern temperate regions. Most cypress species are trees, while a few are shrubs...

forests, suggesting that this was the animal's preferred habitat.

Morphology

Plantetherium measured around 25 centimetres (9.8 in) in length, and its skeleton closely resembled that of its modern relatives. Its teeth already included the comb-like structure distinctive to modern colugos. There is no direct evidence that Planetetherium had the membrane of skin that allows modern colugos to glide, but its bodily proportions suggests that this was likely the case.