However, simians are traditionally excluded, rendering prosimians paraphyletic. Other prosimians are arboreal quadrupeds and climbers. Other prosimians shown include Mohol bushbabies and South East Asia's slow lorises and tarsiers. Like most nocturnal prosimians, dwarf lemurs are reported as living solitary or in pairs. The larger primates never reached Madagascar, making the island a sanctuary for prosimians, especially lemurs. Prosimii included all of the prosimians&colon; Strepsirrhini plus the tarsiers. Related to their frequently nocturnal lifestyle, prosimians lack the colour vision of higher primates. Vertical clinging and leaping has only been observed in primates, and primarily in prosimians. The nocturnal prosimians are mainly solitary. Some prosimians, colobine monkeys and callitrichid monkeys also use this system. Several prosimians are primarily vertical clingers and leapers. Hence most of the prosimians and platyrrhines have three premolars. The "prosimians", on the other hand, form a paraphyletic taxon. Three species of prosimians made their entrance in the zoo. All prosimians possess two laterally flattened toilet claws, used for grooming.