 In 1785 , the Dutch physician and naturalist Pieter Boddaert was the first to officially describe a species of slow loris using the name Tardigradus coucang . This species was based on the " tailless maucauco " described by Thomas Pennant in 1781 , which is thought to have been based on a Sunda slow loris , and on Vosmaer 's description of a Bengal slow loris . Consequently , there has been some disagreement over the identity of Tardigradus coucang ; currently the name is given to the Sunda slow loris . The next slow loris species to be described was Lori bengalensis ( currently Nycticebus bengalensis ) , named by Bernard Germain de Lacépède in 1800 . In 1812 , Étienne Geoffroy Saint @-@ Hilaire named the genus Nycticebus , naming it for its nocturnal behavior . The name derives from the Ancient Greek : <unk> ( <unk> ) , genitive form of <unk> ( <unk> , " night " ) , and <unk> ( <unk> , " monkey " ) . Geoffroy also named Nycticebus javanicus in this work . Later 19th @-@ century authors also called the slow lorises Nycticebus , but most used the species name tardigradus ( given by Linnaeus in 1758 in the 10th edition of Systema Naturæ ) for slow lorises , until mammalogists Witmer Stone and James A. G. Rehn clarified in 1902 that Linnaeus 's name actually referred to a slender loris . 
