Strepsirrhini or Strepsirhini is one of the two suborders of primates. Strepsirrhines include the lemuriform primates, which consist of the lemurs of Madagascar, galagos ("bushbabies") (pictured) and pottos from Africa, and the lorises from India and southeast Asia. The suborder also includes the extinct adapiform primates, a diverse and widespread group that thrived during the Eocene (56 to 34 million years ago—mya) in Europe, North America, and Asia, but disappeared from most of the Northern Hemisphere as the climate cooled. Adapiforms are sometimes referred to as being "lemur-like", although the diversity of both lemurs and adapiforms do not support this comparison. The suborder represents a phylogenetic clade, or related group, and replaced the widely used suborder Prosimii, which included strepsirrhines and tarsiers, but represented an evolutionary grade based on shared anatomical traits. The term "prosimian" is considered obsolete taxonomically, though still useful in highlighting similarities between strepsirrhines and tarsiers.
Strepsirrhines are defined by their "wet nose" or rhinarium. They also have a smaller brain than comparably sized simians (monkeys and apes), large olfactory lobes for smell, a vomeronasal organ to detect pheromones, and a bicornuate uterus with an epitheliochorial placenta. Their eyes contain a tapetum lucidum (reflective layer) to improve their night vision, and their eye sockets include a bony ring (postorbital bar), but they lack a wall of thin bone behind the eye (postorbital closure). Strepsirrhine primates produce their own vitamin C, whereas haplorhine primates (tarsiers and simians) must have it supplemented in their diet.