neck muscles attach). Unlike Palaeopropithecus the rims of the orbits (eye sockets) were not as thick. The area of the orbit was , comparable to that of gorillas. Based on the ratio of its orbit area to the size of its optic canal, Archaeoindris had low retinal summation, meaning its eyes were less sensitive to light (like living diurnal lemurs). Yet the ratio was not as low as in comparably sized apes, suggesting Archaeoindris had low visual acuity and lacked trichromatic color vision. The jaw exhibited a long, robust mandibular symphysis (joining of the two halves of the lower jaw), which fused early during development. Its palate (bones on the roof of the mouth) was rectangular. Like other sloth lemurs, it likely experienced accelerated dental development, and had an adult dental formula of . Its teeth were also similar to those of Palaeopropithecus, both in morphology and proportions. The four lower incisors that would have made up the toothcomb were modified, being shorter and more robust, possibly for feeding purposes. The canines were short and stout, but sharp. Also, there was a diastema (gap) between the lower premolars (p2 and p4). Other dental similarities with Palaeopropithecus included small third upper and lower molars (M3 and m3), the first and second molars were narrow and long, and the enamel of its cheek teeth was crenulated (low and rounded), though not as wrinkled and slightly higher-crowned. Most bones of the postcranial skeleton, including the bones of the hands, feet, vertebral column, ribs, radius (lower arm bone), tibia, and fibula, have not been found for Archaeoindris. As with many cranial features, the postcranial bones that have been discovered are similar to that of Palaeopropithecus, but significantly larger and more robust. The head of the femur was large and lacked a fovea capitis femoris (a small depression in the head of the femur). The femur was short and extremely robust, had a very high collodiaphyseal angle (the angle of the neck and shaft of the bone), and the greater trochanter was small. In the adult, the humerus was significantly longer than the femur, while in the immature specimen, both the humerus and ulna were much longer than the femur, making the arms considerably longer than the legs, as also seen in Palaeopropithecus. The relative length of the arms to the legs was shorter in Archaeoindris, so although its intermembral index was over 100, it