 Lorises first appear in the Asian fossil record in the Miocene , with records in Thailand around 18 million years ago ( mya ) and in Pakistan 16 mya . The Thai record is based on a single tooth that most closely resembles living slow lorises and that is tentatively classified as a species of Nycticebus . The species is named ? Nycticebus linglom , using open nomenclature ( the preceding " ? " indicates the tentative nature of the assignment ) . Several lorises are found in the Siwalik deposits of Pakistan , dating to 16 to 8 mya , including <unk> and <unk> . Most are small , but an unnamed form dating to 15 – 16 mya is comparable in size to the largest living slow lorises . Molecular clock analysis suggests that slow lorises may have started evolving into distinct species about 10 mya . They are thought to have reached the islands of Sundaland when the Sunda Shelf was exposed at times of low sea level , creating a land bridge between the mainland and islands off the coast of Southeast Asia . 
