The same that they use for the rest of the already known tiger cat species?! This one diverged from its closest relatives 1.3 million years ago. There are other tiger cat species that diverged later than that. Read the paper if you want to know more. You sound like there’s a >epsilon probability you, a random HN reader, found a gotcha in a paper by the experts of the field because you’re so smart that you know that the definition of "species" is sometimes fluid. Great job, I’m sure the authors don’t know that.