Taxonomy
Traditionally, only Semnopithecus entellus was recognized as a species, the remainder all being treated as subspecies. In 2001, it was proposed that seven species should be recognized, with the majority considered monotypic. This was followed in Mammal Species of the World in 2005, though several of the seven species intergrade, and alternative treatments exist where only two species (a northern and a southern) are recognized. Phylogenetic evidence supports at least three species (a north Indian, a south Indian and a Sri Lankan species). It has also been suggested that Semnopithecus priam thersites is worthy of treatment as a species rather than a subspecies, but at present this is based on limited evidence.
It has been suggested that Trachypithecus should be considered only a subgenus of Semnopithecus. If maintaining the two as separate monophyletic genera, the purple-faced langur and Nilgiri langur belong in Semnopithecus instead of the usual Trachypithecus. At present it is unclear where the T. pileatus species group (consisting of the capped langur, Shortridge's langur and Gee's golden langur) belongs, as available mtDNA data place it in Semnopithecus, while Y chromosome data place it in Trachypithecus.
The seven species of Semnopithecus recognized in Mammal Species of the World are:
- Nepal gray langur Semnopithecus schistaceus
- Kashmir gray langur Semnopithecus ajax
- Tarai gray langur Semnopithecus hector
- Northern plains gray langur Semnopithecus entellus
- Black-footed gray langur Semnopithecus hypoleucos
- Southern plains gray langur Semnopithecus dussumieri
- Tufted gray langur Semnopithecus priam
Read more about this topic: Gray Langur