 Despite the similarities, there are several features that distinguish Mesopropithecus skulls from those of living indriids. The skull, including the zygomatic arch, is more robustly built. The temporal lines join together anteriorly into a sagittal crest and there is a distinct nuchal ridge that joins the rear of the zygomatic arch. 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. The upper incisors and canines are larger. The more robust mandible (lower jaw) and mandibular symphysis (point where the two halves of the lower jaw meet) suggest a more folivorous diet, which requires extra grinding. The orbits are as large (in absolute size) as those in smaller living indriids, which suggests low visual acuity. Mesopropithecus and its closest sloth lemur relative, Babakotia, did share a few ancestral traits with indriids, unlike the largest sloth lemurs, Palaeopropithecus and Archaeoindris. These include the aforementioned four-toothed toothcomb, an inflated auditory bulla (bony structure that encloses part of the middle and inner ear), and an intrabullar ectotympanic ring (bony ring that holds the eardrum).
