Back on January 11, I read this on twitter:
Hm? What was that about?
Panthera atrox was a big cat in the fullest sense of those words. Significantly larger than the modern lion, it roamed what is now the United States until a global deep freeze killed it off around 11,000 years ago.
For various reasons, P. atrox was classified from the outset as part of the lion family. But for decades, some scientists pushed back against this leonine designation. They argued that the beast shared too many jaguar affinities to be classified as any other kind of big cat. In 2009, a paper by Per Christiansen and John Harris claimed to settle the debate. Comparatively analyzing the skull morphologies of different species (apparently more or less the same way Christiansen studied clouded leopards), the authors boldly stated that “Panthera atrox was no lion.” Instead, they proposed, “A possible scenario for evolution of P. atrox is that it formed part of a pantherine lineage that … gave rise to the extant jaguar.” As P. atrox, in these authors’ estimation, was no longer a lion, but rather something jaguar-ish, it was due a new name. To honor an ancient-mammal enthusiast and donor to the Natural History Museum of L.A. County, P. atrox was christened “Naegele’s giant jaguar” [pdf].
Because P. atrox was originally classified as a lion, however, it is more likely that you know it as the “American lion.” And over the decades, this leonine designation has largely resisted any jaguar-ish pushback. In 2009, a paper by Ross Barnett and colleagues claimed to settle the debate [pdf]. Comparatively analyzing the DNA of different extant and extinct big-cat species, the authors dispassionately stated that “all late Pleistocene lion samples produced sequences that grouped strongly with modern lion data, rejecting any postulated link between atrox and jaguar.” Indeed, they said, P. atrox was a lion — or at least something lion-ish. If we accept this classification, then P. atrox may keep and proudly bear the “American lion” moniker.
In my world, DNA analysis trumps skull morphology. “American lion” wins.
But I’m not the final arbiter of such things. As long as there’s a dispute, poor P. atrox must suffer from an identity crisis. For now, it’s still a beast with two names.
Note: For those interested in more detail on the dueling 2009 P. atrox studies and the quite divergent implications of the two different proposed classifications, the estimable Brian Switek has a much longer read on the topic.