The Cave Lion (Panthera spelaea and Panthera fossilis)

[tigerluver]

It's interesting to note that P. shawi is from South Africa, thousands of miles away from where the cave lion stem group would have migrated from. While a continuous population of lion-stem group in Africa is likely, P. shawi must have still become somewhat distinct from the cave lion stem due to allopatric, spatially-produced speciation. 

Back to the P. spelaea-P. fossilis issue. One option is that we stick to what the Barnett et al. (2016) proposed and stick P. fossilis into the P. spelaea branch directly as follows:

*This image is copyright of its original author

The support for this approach would be that that there is a clear chronological distinction between the two cave lion forms in fossil record, thus leaving the option that P. s. fossilis (as described by this theory) was the earlier P. spelaea signified by the light blue branch which in time morphed into P. spelaea spelaea (signified by the indigo branch) as proposed by Marciszak et al. (2014). The assumption this theory makes is that we have not missed any P. spelaea spelaea specimens that predate or are contemporary to P. fossilis. It also assumes that P. fossilis is genetically not much different than P. spelaea and can safely be placed as a species on the P. spelaea evolutionary branch.

The second assumption is what meets adversity. There is clear morphological distinction between the skulls of P. fossilis and P. spelaea. One would assume that morphological differences warrant genetic differences, thus affecting the above phylogenetic tree. Sotnikova and Foronova (2014), Sotnikova and Nikoskyi (2006), and Hanko and Korsos (2007) believe the morphological differences are hefty enough to warrant speciation, while Marciszak et al. (2014) takes these difference as subspecific. If P. atrox, which is similar to P. fossilis according to Sotnikova and Foronova (2014) is by consensus considered a distinct species from P. spelaea, than it would make most sense to treat P. fossilis the same.

I modified the phylogenetic tree to observe different options. Disclaimer, this is all very crude and some movements may not be yet supported by the genetic data. 

If we go with P. fossilis as distinct, we could modify the phylogeny in this way:

*This image is copyright of its original author

This would indicate three branching from the stem group. We could stick P. fossilis as an earlier branch as follows:

*This image is copyright of its original author

Neither model is supported by fossil record, but that could just attributed to a lack of data. Nonetheless, as it stands, neither model can validated until we find older P. fossilis specimens or DNA test the specimens we do have. 

Another phylogenetic modification could be using the Sabol (2011) hypothesis. 

*This image is copyright of its original author

For such a model, the confidence intervals have to respected the emergence dates shifted within the confidence interval range. As the new emergence date of P. spelaea would still be within the 95% CI, this would not be a completely invalid model. This model would also incorporate Hanko and Corsos' (2007) that P. fossilis was closer to P. leo than P. spelaea is to P. leo. Based on the chronological fossil record and the aforementioned studies that do give convincing reason that P. fossilis and P. spelaea are not exactly a chronological product of the same lineage, this last model may be the most accurate. Reply