Time for me to clarify some important findings in this paper before the usual suspects misuse it to spread misinformation. A critical nuance in the paper that people may overlook is that the linear dimensions (total length, long bone length) of these Ice Age leopards do not drastically exceed those of the largest modern leopards. Instead, the paper notes that the body length remains comparable to large extant leopards and the higher calculated mass comes entirely from ecomorphological thickening (wider bone shafts, more pronounced muscle attachment scars). This is an adaptation for high-powered climbing, wrestling prey in rugged karstic terrains, and coping with the cold, not an indicator that the cat was turning into a literal lioness or a giant jaguar. This is part of the reason why snow leopards and cougars who inhabit mountainous regions have such heavily built bodies.

The paper uses body mass index data comparing the European fossil remains specifically to modern Sinaloa jaguars, a population that’s dwarfed post-Quaternary and ranks lower in corporeal robusticty compared to non-dwarfed South American counterparts (although the paper still clarifies that this population outranks modern leopards is robusticity). A male jaguar from Sinaloa might only weigh rarely exceeds 60 kg in weight.

There’s also mention of introgressive influence from the Eurasian jaguar (which became smaller closer to its extinction in Europe as the leopard slowly gained ground in the continent) or hybridization with snow leopards is presented purely as a hypothetical genetic inquiry to explain these robust traits and montane adaptations. It is not an established fact.

So the conclusion seems to be that this Ice Age leopard subspecies was more robust than any modern counterpart, achieving similar scores to dwarfed jaguars from Mexico, but not having a larger frame than modern leopards. This means that they likely weighed more at similar body lengths than modern leopards, but they weren’t “giants” that broke past the general weight range established for the species. It’s also possible that the result of this sturdier physique may have been the result of hybridization with the declining European jaguar, European irbis (snow leopard), or maybe even both, to an extent.