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a suborder of mammals of the order Primates. There are six families: Tupaiidae (tree shrews; some zoologists assign the family to the Insectivora), Lemuridae (lemurs), Indridae (the type species is the indri), Daubentoniidae (with a single species, the aye-aye), Lorisidae, and Tarsiidae (tarsiers). The prosimians are represented by 26 genera, embracing approximately 50 species.
The body ranges in length from 13 cm (mouse lemurs) to 70 cm (indri) and in weight from 60–100 g (mouse lemurs) to 2 kg (ring-tailed lemur). Most prosimians have long tails; however, in Lorisidae, the tail is short or absent. The arms are usually shorter than the legs, and the thumbs and big toes are for the most part mobile and opposable to the rest of the digits (except in tree shrews). The fur is dense and often brightly colored. The brain has few sulci and convolutions. Most prosimians have 36 teeth; however, tree shrews have 38, and tarsiers 34. There are one to three pairs of mammae.
Prosimians inhabit the tropics of Africa and Madagascar. They are also encountered in Asia and on the islands of the Malay Archipelago. The animals are mainly arboreal. They bear one to three young per birth. The numbers of many species, especially on Madagascar, are diminishing sharply. Protection is necessary.