Neopropithecus Lamberton, 1936 Mesopropithecus is an extinct genus of small to medium-sized lemur, or strepsirrhine primate, from Madagascar that includes three species, M. dolichobrachion, M. globiceps, and M. pithecoides.

M. dolichobrachion also consumed a mixed diet of fruits and leaves, but analysis of its teeth suggests that it was more of a seed predator than the other two species.

Known only from subfossil remains, it died out after the arrival of humans on the island, probably due to hunting pressure and habitat destruction.

Mesopropithecus is a genus within the sloth lemur family (Palaeopropithecidae), which includes three other genera: Palaeopropithecus, Archaeoindris, and Babakotia.

[3][6][8][9] Unlike the indriids, but like the sloth lemurs, they had elongated forelimbs and other adaptations for arboreal suspension (hanging in trees), linking them most closely to family Paleaeopropithecidae.

The skull has a more rounded braincase, slightly smaller and more convergent orbits, more pronounced postorbital constriction (narrowing of the skull behind the eye sockets), more robust postorbital bar (bone that encircles the eye socket), a steeper facial angle, more robust and cranially convex zygomatic bone, and a broader, squared snout.

Until recently, important pieces of the skeleton had not been discovered, including the radius, ulna, vertebrae, hand and foot bones, and the pelvis.

In 1936, Alice Carleton mistakenly associated postcranial remains of the diademed sifaka (Propithecus diadema) from Ampasambazimba with Mesopropithecus pithecoides and came to the false conclusion that its morphology was like that of a monkey.

[2] Subfossil discoveries indicate that they lived in the same region (sympatric) with other sloth lemurs in the north and center of Madagascar.

[3] M. pithecoides from the central plateau was a specialized leaf-eater (folivore), but the other two species had a more mixed diet, eating fruits and seeds in addition to leaves.

[14] Because Mesopropithecus died out relatively recently and is only known from subfossil remains, it is considered to be a modern form of Malagasy lemur.

[12] It may have been among the last subfossil lemurs to go extinct, possibly surviving until 500 years ago,[1][30] although radiocarbon dating places the most recent remains at 570–679 CE for a M. pithecoides from Ampasambazimba.

[3][30] The arrival of humans roughly 2,000 years ago is thought to have sparked the decline of Mesopropithecus through hunting, habitat destruction, or both.