Strepsirrhini

Strepsirrhini is a suborder of primates that includes lemurs, lorises, and galagos, along with their extinct relatives. They are distinguished from the other primate suborder by features adapted to a greater reliance on the sense of smell and nocturnal activity, such as a moist rhinarium, a prominent snout, and a grooming claw on the second toe. A toothcomb formed by the lower incisors and canines is used for grooming, and many species retain a tapetum lucidum, which contributes to eyeshine in dim light. Their brains are generally smaller relative to body size than those of the haplorhine primates.

Strepsirrhini comprises two infraorders: Lemuriformes (lemurs) and Lorisiformes (lorises and galagos). The lemur lineage is concentrated in Madagascar and nearby islands, with families including Lemuridae, Cheirogaleidae, Indriidae, Lepilemuridae, and Daubentoniidae (aye-aye). The lorisiform lineage includes the families Lorisidae (lorises and pottos) and Galagidae (galagos).

Ecology and behavior are varied within the suborder. Most strepsirrhines are arboreal and nocturnal, though several lemur species are diurnal. Diets range from fruit, nectar, and leaves to insects, with specialized feeders such as the aye-aye targeting grubs within wood. Reproduction is often seasonal, with small litter sizes and extended maternal care; many species exhibit distinct mating seasons and prolonged development.

Evolutionary note: Strepsirrhini diverged from haplorhine primates early in primate evolution. Madagascar’s long isolation has fostered the unique lemur radiation, while lorises and galagos occupy mainland Africa and parts of Asia. The suborder remains a key group for understanding primate evolution, sensory biology, and biogeography.