Gliding Lemur, Colugo, Cobego ( Cynocephalus volans, C. variegatus) Not uncommon, as there is a huge niche for this leaf-eater, but little known because it is inconspicuous in the canopy during the day, this taxon is central to debate about the origin of bats. It is the only known glider with all forelimb and hindlimb digits enclosed within the gliding membrane (patagium).
For this reason it is the only extant mammal that could provide a glimpse of the putative gliding ancestors of bats.
While the prevailing current opinion would put a colugo-like ancestor to both kinds of bats, note that there is a viable alternative which puts the colugo-like ancestor before the megabats, but after the microbats.
In other words, the colugo is a crucial taxon in the flying primate dispute.
Features that link the colugo to the megabats, but not to the microbats, include locomotion, defaecation (they both demurely get into the upright posture by hanging from their thumbs!...in contrast to the microbat's arched back "slice"), reproduction.
The most remarkable recent information about the colugo is the confirmation from molecular biology and from neuroanatomy that it is a very close primate relative. This was Linnaeus original classification, rejected since.
I have pointed out that the colugo may escape detection as an obvious primate relative because it has a small-brain, large ventricle syndrome that it shares with the koala and three-toed sloth, two other exclusive folivores. The problem may be phenotypic, all three of these taxa being exposed to high levels of phyotoxins that cause developmental disturbances that take each of them out of the normal range of variation of brain size for their group.