Semnopithecus leucoprymnus

Date 1838
Source https://www.flickr.com/photos/biodivlibrary/6288742885
Author Georges Louis Leclerc Buffon; Imprimerie de Lacrampe; Lesson, R. P.
Full title Compléments de Buffon / par P. Lesson.
Source: https://commons.wikimedia.org/wiki/File%3ACompl%FF%FFments_de_Buffon_%286288742885%29.jpg

The purple-faced langur (Semnopithecus vetulus), also known as the purple-faced leaf monkey, is a species of Old World monkey that is endemic to Sri Lanka. The animal is a long-tailed arboreal species, identified by a mostly brown appearance, dark face (with paler lower face) and a very shy nature. It had traditionally been classified within the lutung genus Trachypithecus but was moved to the genus Semnopithecus based on DNA evidence indicating that is it more closely related to the gray langurs.

Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Cercopithecidae
Genus: Semnopithecus
Species: Semnopithecus vetulus (Erxleben, 1777)
Synonyms: Trachypithecus vetulus