The Cave Lion (Panthera spelaea and Panthera fossilis)

[tigerluver]

With a few words, I made an indication that I found P. fossilis to have proportionately longer tarsal and carpals than other pantherines. Here's my basis. 

First I noticed that in Marciszak's figures, P. fossilis, both the early and middle form, consistently had longer metacarpal and metatarsals than P. spelaea. 

*This image is copyright of its original author

Thus, I would expect P. fossilis handful of long bone specimens to show the same trend. This was not the case. Something could have been different, namely the proportions of distal to proximal bones of the species. However, with a small sample size for P. fossilis, analysis is difficult. Nevertheless, I consulted the realms of biostatistics, utilizing the confidence interval. I tested two proportions, namely the ratio of femur length to tibia length and the ratio of femur length to metatarsal III (3) length.:

*This image is copyright of its original author

What you see above are the different ways I used the true average, the minimum 95% interval average, and the maximum 95% interval average for each bone measurement. By mixing and matching different intervals, I calculated different ratios. The then averaged these ratios to come up with a statistically most likely value for each ratio. This way, I attempted to make something more concrete out of a few pieces.

The results show that in all likelihood, P. spelaea and P. fossilis did significantly different in proportion. To account for the small sample size, I derived the p-value at a confidence level of 99% (alpha = 0.01), meaning there is only 1% chance these tests produced a false result, at least by the rules of biostatistics. As you can see above, both tests' p-values were comfortably below the cutoff for significance in different of 0.01, meaning nothing here is a borderline conclusions. 

Therefore, tentatively it seems P. fossilis was a longer legged cat than P. speleaa by quite a bit. Thus, it would have been a very, very tall cat. The fact that distal bones (tibia and metatarsal 3) are proportionately longer than proximal bones (femur) also indicates that P. fossilis was more cursorial than P. spelaea. By extension, as P. leo shares its ratios with P. spelaea, P. fossilis would have been quite proportionately taller and more cursorial than its closest living relative in P. leo.  


What is interesting to note is that despite this seemingly higher rate of cursoriality, P. fossilis does not seem to have given up robusticity. The giant 465 mm ulna I found to be about the same in robusticity as the American lion (P. atrox), a species with a femur to tibia almost the same as P. spelaea. Moreover, looking the humerus fragment, Thus, P. fossilis could be looked as a paradigm for the peak of evolutionary efficiency. It was a long limbed cat, well adapted for covering distance perhaps more effectively than the modern lion. Yet at the same time, it also had bones wider than the modern lion, indicating a powerful beast capable of bringing down the Pleistocene's big game. This combination is hard to find in any modern carnivore. All in all, it seems P. fossilis is unique. It had wide bones, part of which was used for increased muscle mass and another part which aided its long legs as they strode during its cursorial life. 

Another interesting aspect to note is that in the Marciszak et al. (2014), earlier P. fossilis consistently had longer metacarpals and metatarsals than the middle P. fossilis. Perhaps this could be used as a line of evidence for the chronological link between P. fossilis and P. spelaea, whereby the intermediate proportions of the tarsals and carpals in the middle P. fossilis is proof a transition period in the lineage. Perhaps these late middle Pleistocene P. fossilis are also the direct ancestors of P. atrox, explaining why P. atrox, while sharing skull characteristics with P. fossilis, did not share its proximal to distal bone proportions. Thus, the next step could be to investigate the climate and habitat changes that could have triggered the body proportion change. Reply