The endemic Thomas’s flying squirrel, Aeromys thomasi (Hose, 1900) of south Sarawak, around 1000m ASL.

Females of the Thomas’s flying squirrel reach a head-torso length of 343.3 mm, a tail length of 410 mm and a weight of 1117 g. Males were measured to have a head-torso length of 300 mm and a tail length of 370 mm. The species is larger than its closest relative, the black flying squirrel (Aeromys tephromelas). The species name refers to the English zoologist Michael Rogers Oldfield Thomas. This species is found high up in the trees and is locally endemic in Borneo. This species is more common in the highlands than in the lowlands, so the habitat appears to be above 800m above sea level. Borneo is a biodiversity hotspot for flying squirrels with 14 species all over Borneo.