Indriids are medium- to large-sized prosimians. The extinct species Archeoindris fontoynonti weighed up to 400 lb (181 kg), while the smallest species in the family, the eastern woolly
lemur Avahi laniger, weighs about 2.3 lb (1 kg). Most indri-ids have tails shorter than their bodies, with the tail of the in-dri reduced to a few inches (about 5 cm). The extant indriids are magnificent leapers, with hind limbs longer than their forelimbs. Ears are small, bare or tufted, and rounded. The skin of the face is bare, and the snout is foreshortened. The eye color is often brown in woolly lemurs, orange or amber in sifakas, and yellow-green in indris. The fur is short, dense, and of various colors including brown, beige, white, orange, and black; often with head crowns, head ruffs, saddle backs, and eyebrows contrasting colors from the rest of the body. Indriids have five fingers on each of its two forefeet and five toes on each of its two hind feet; all with bare nails, except for the grooming claw on the second digit of their feet. Males have central chest scent glands, and females have anal scent glands.
Indriids have a dental tooth comb and small upper incisors with a reduced dental formula of only two premolars and four, rather than six, teeth in their tooth comb. Indriids retain the primitive primate features of a simple postorbital bar, relatively small brain case, and a well-developed rhinarium. All species of indriid, whether nocturnal or diurnal, have reflective eyes (tapetum lucidum) to increase perception in low light levels. Indriids are uniform in their cranial morphology and have a tympanic ring that lies free in the bulla and a large
stapedial artery. The digestive tract has an enlarged caecum and a large intestine for digesting vegetation.
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