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 Black-footed Grey Langur S. hypoleucos which has a restricted range in southwest India. This photo was taken at the Someshwara Wildlife Sanctuary at Agumbe in Karnataka. I also saw them at the Tholpetty Wildlife Sanctuary in Kerala, but unfortunately didn't manage to get good photos of them at either location (see here for a photo from Tholpetty: Black-footed Grey Langur (Semnopithecus hypoleucos) | ZooChat).
Vivek Menon in his field guide to Indian mammals gives this species a large range because he doesn't recognise S. dussumieri, instead combining that species' southerly populations with S. hypoleucos.
