A prosimian is the most primitive type of primate. Prosimians are ancestral to all of today's monkeys and apes, including humans. The group includes all of the lemurs, tarsiers, and lorises.

 

Prosimians are typically, but not exclusively nocturnal, and have lower brain-to-body mass ratios than other primates. Their habitat is restricted to tropical woodlands.

 

Prosimians are characterized by:

 

• a well-developed sense of smell with snout

 

• only partial binocular vision

 

• claws on some digits

 

• immobilized upper lips

 

• a 2:1:3:3 dental formula, i.e., 2 incisors, 1 canine, 3 premolars, 3 molars.

 

Phillipine tarsier (Tarsius syrichta). The tarsier is so named because of its elongated tarsals or foot bones. These enable it to leap great distances.