What is a Panda, really?

A whole day of snow today, so here's a shot of a critter that knows a thing or two about the subject:

Red Panda (Ailurus fulgens),
Lincoln Park Zoo, Chicago, IL 11/30/2013

This, of course, is a Red Panda*, (Ailurus fulgens). They are residents of China and the eastern Himalayan countries, and are currently listed as vulnerable, with decreasing populations throughout their range.

Red Pandas provide a fascinating lesson in how our views towards classification have changed over the years. It's been called a Raccoon (family Procyonidae, otherwise only found in the New World), an aberrant bear (family Ursidae), or a member of a family of Pandas (Ailuripodidae, including it and the Giant Panda, Ailuropoda melanoleuca). The idea, of course, is that we know that we have this critter, now we need to figure out what it really is -- which means finding which taxonomic folder it belongs in and stuffing it in there.

Modern DNA analysis has done wonders for our taxonomic efforts, but even before they became widespread, a more modern view of taxonomy had started to take effect. Called cladistics, it attempts to apply an explicitly evolutionary model to whatever critters we're working on, defining a taxonomic group purely on common ancestry. Ideally, a name is applied to a group if and only if that group includes all of the descendants from a particular ancestor, sometimes dubbed the LCA (from last common ancestor, of course). This sort of group, formally called a "clade", is described as monophyletic. Leaving out descendants (say, non-flying mammals) would produce a paraphyletic group, and adding unrelated species (say, fish and whales) would produce a  polyphyletic group.

The Red Panda's lineage apparently split from the LCA of weasels and raccoons around 39 million years ago, about 7 million years before the weasels and raccoons parted ways. (1) Since we consider the weasels and raccoons to be separate families, there isn't anywhere to put the Red Panda to keep the groups monophyletic, so it gets its own family (Ailuridae). Instead of figuring out what the Panda "really is", we've figured out what the evolutionary history behind it "really is" and then shaped our groups, and names, to fit.

This leads some authors to label the Red Panda a "living fossil", which is a truly oxymoronic name: fossils are defined as traces of living things more than 10,000 years old. But does it even apply in this case? Yes, this group split off quite early, but obviously it's still around today. And it turns out that the family used to be much more important -- there are quite a few fossil species, ranging from China to England, and recent finds in several parts of North America. (2) So what we have is not a single lineage that has somehow survived till now, but a widespread group that is only recently down to one species. (Actually, most 'living fossils' fit this description, I guess.)

The loss of those other species suggests that the Red Panda is doomed to eventual extinction -- but that actually describes every creature on Earth. For now, we're all vibrantly, exuberantly alive, and I can't help but feel that exuberance just a bit more when I'm watching this shining little critter.

*A Red Panda actually played an important, if unsung, role in a couple of recent movies. If you've ever seen Kung Fu Panda and wondered what sort of animal Master Shifu was, well, he's a Red Panda!

(1) http://www.onezoom.org/mammals.htm

(2) Naish, Darrin (2008-04-05). "The once mighty red panda empire". Tetrapod Zoology. Retrieved 9 January 2010.