Madagascar's giant sloth-like lemur
Palaeopropithecus, also known as the sloth lemur, was a large primate that lived in the forests of Madagascar until a few centuries ago. Three species are known: P. ingens, P. maximus, and the smaller P. kelyus. The largest of these species weighed between 40 and 60 kilograms, far exceeding the weight of today's largest living lemur, the indri, which weighs around 9 kilograms. The name sloth lemur comes from its highly specialized mode of movement, which involved hanging upside-down from branches and moving slowly through the canopy. This suspensory locomotion was made possible by its unique anatomy.
The sloth lemur had forelimbs that were significantly longer than its hindlimbs, a feature shared with modern orangutans and gibbons. Its hands and feet possessed extremely long, curved phalanges that formed powerful hooks for gripping branches. This structure made it one of the most suspensory mammals ever to have evolved. While perfectly adapted for life in the trees, this specialization made movement on the ground difficult and likely rare. Analysis of their skulls shows they had relatively small eye sockets, suggesting they were active during the day. Their diet consisted mainly of leaves, fruits, and seeds, a conclusion supported by the wear patterns and robust structure of their teeth.
Extinction by eagle and man
The sloth lemur survived well into the period of human settlement on Madagascar. Radiocarbon dating of subfossil remains indicates that Palaeopropithecus may have survived until between 1300 and 1620 CE. Its extinction is attributed to a combination of factors, primarily driven by the arrival of humans. The slow, deliberate movements of the sloth lemur would have made it an easy target for hunters. Direct evidence of this comes from fossil bones discovered in the early 20th century that show distinct cut marks. These marks, found near joints, are consistent with skinning, disarticulation, and filleting for meat by early human colonists.
Humans were not their only predators. Sloth lemurs were also hunted by the Malagasy crowned eagle (Stephanoaetus mahery), a large bird of prey that also went extinct around 1500 AD. This powerful eagle was larger than its living relative, the African crowned eagle, which is known to prey on animals larger than itself. The slow, arboreal lifestyle of Palaeopropithecus would have made it vulnerable to aerial attacks. Today, living lemurs in Madagascar still show an instinctive fear response to the silhouettes of birds of prey, a possible result of predation by this giant eagle. The combination of human hunting and habitat destruction led to the disappearance of the sloth lemur, a loss of Madagascar's unique primate diversity.