New species of vertebrates are discovered only very rarely. New mammal species are even rarer, and large species of mammal are the rarest.

Which is why it’s so friggin’ exciting that this week scientists have announced that the clouded leopard of Borneo is in fact a species in it’s own right, as opposed to a subspecies of the mainland clouded leopard of southeast Asia.

Here’s the mainland species, Neofelis nebulosa:

And here’s the Bornean species, Neofelis diardi:

It can actually be very difficult to tell what is a species and what isn’t – the traditional litmus test is to see if getting the males and females together produce viable offspring (horses and donkeys for example produce sterile mules – hence they are not the same species). But it’s not always that simple. In this case, researchers used sophisticated DNA typing methods to determine how long ago the two cat species diverged on the evolutionary tree – about 1.4 million years. The 40 single DNA differences between them are apparently enough to consider them different species.