Until fairly recently all the Grey Langurs of the south-Asian genus Semnopithecus were lumped as one species, S. entellus. Now they have been split into about seven or eight species. They are distinguished not only by their genetics but also visibly by colouration (especially of the limbs) and by tail carriage (i.e. whether the tail is carried looped forwards or backwards).
I have recently seen four of the species in India (priam, dussumieri, hypoleucos and ajax) so am uploading photos of all four for comparitive purposes.
This pictured species is the Southern Plains Grey Langur S. dussumieri of (roughly) western India. These photos were taken at the Sariska Tiger Reserve in Rajastan. Vivek Menon in his field guide to Indian mammals doesn't recognise this species, instead combining the more northerly populations with the eastern S. entellus (giving entellus a combined range across the bulk of India), and the southerly ones with S. hypoleucos.
