noun, plural: prosimians
Primates are placental mammals that may be grouped into prosimians and simians. Prosimians are characterized by their rather primitive features compared with those of simians. They include lemurs, lorisoids, tarsiers, adapiforms, and non-simian omomyids. Simians include hominins, apes, and monkeys. The simian line and the tarsier line diverged during the Cenozoic era, i.e. about 60 million years ago.
The prosimians are characterized morphologically by having large ears and eyes. They lack the colour vision but they have an enhanced vision under low-light conditions. They are nocturnal and arboreal predators. Their diet is comprised largely of insects and small animals. They also have two laterally flattened grooming claws used for personal grooming. However, the position of the grooming claws may vary. For instance, the grooming claws are found on the second and third toes of the tarsiers whereas those in lemurs and lorises are found on the second toe.
The prosimians are paraphyletic group. Apart from the non-tarsier prosimians belonging to the suborder Strepsirrhini of the order Primates, they also include the tarsiers and the omonyiforms belonging to the suborder Haplorrhini.
Word origin: Greek pro (before) + Latin simius, simia (ape)