Megaladapis was quite different from any living lemur. Its body was squat and built like that of the modern koala. Its long arms, fingers, feet, and toes were specialized for grasping trees, and its legs were splayed for vertical climbing. The hands and feet were curved and the ankles and wrists did not have the usual stability needed to travel on the ground that most other Lemurids have. Its head was unlike any other primates, most strikingly, its eyes were on the sides of its skull like all other primates. Its long canine teeth and a cow-like jaw formed a tapering snout. Its jaw muscles were powerful for chewing the tough native vegetation. Its body weight reached about 110 lbs. The shape of its skull was unique among all known primates, with a nasal region which shoed similarities to those of rhinoceros, what was probably a feature combined with an enlarged upper lip for grasping leaves. An endocast of the skull was taken and it was found that the brain capacity was about 250cc. This is about 3 to 4 times the size of a common cat's.
Megaladapis evolved because the island's topography was always changing. Along with the other lemurs, Megaladapis specialized within its own niche. The general expectations of tree climbers such as Megaladapis is that with an increase in size, the body's forelimbs will also increase proportionally.
It is often believed that Malagasy legends of the tretretretre or tratratratra, an extinct animal, refer to Megaladapis, but the details of these tales, notably the "human-like" face of the animal, match the related Palaeopropithecus much better.
When humans arrived, between 1,500 and 2,000 years ago, the archaeological record shows that they cleared large areas of the island using "slash-and-burn" techniques. Unable to adapt to the environmental changes and the presence of humans, Megaladapis became extinct approximately 500 years ago.
Megaladapis has been found around the marsh of Ambolisatra on the southwestern side of Madagascar and was one of multiple Megafauna that went extinct on Madagascar during this time period. They were also slow-moving creatures that were active during the day. This might have made them more susceptible to predators, forest fires, habitat destruction, and possibly introduced pathogens.