Everyone knows about monkeys and apes, right? Well, there is a third gourp of primates many people are not aware of or do not readily recongnize as primates. They are called prosimians. Prosimians are often described as “primitive” primates. In fact, the name means “before monkeys”. Some of the anatomical characteristics of prosimians are found in other mammal species, but not in monkeys and apes. These include the tapetum (a reflective layer in the retina of the eye that facilitates night vision) and a moist rhinarium ( a structure of the nose that enhances the sense of smell). The skulls of prosimians have smaller brain cases than monkeys and apes and they do not have closed eye sockets. The two halves of the lower jaw are mobile, not fused together. Their reproductive anatomy also differs from other primates in that they have a different shaped uterus (bicornuate) and a different type of placenta (epitheliochorial). Many prosimians produce litters rather than single infants.
Prosimians are subdivided into three groups, including lorids, galagos (or bush babies) and lemurs. They are endemic (only native to) the continents of Africa and Asia and the island of Madagascar, respectively.