Freak Felids - A Discussion of History's Largest Felines

[tigerluver]

I prepared this chart to supplement questions 1 and 2:

*This image is copyright of its original author

GSL = greatest skull length
CBL = condylobasal length
ZGW = zygomatic width

1. As posted, the CBL/GSL ratio from this sample is .9083. From what I've seen, lions fall close with this ratio. 

2. American lions seemed to have zygomatic arches thinner arches. Christiansen and Harris (2009) found the average ZGW/CBL ratio to be 0.686. From that study, they published the average ZGW/CBL of the follow:
Lions: 0.721
Jaguars: 0.736
Tigers: 0.737

From the data, P. atrox seems to have significantly thinner arches, so in a way, a thinner skull.  The thinner skull trait is shared by P. s. fossilis as well. But here's the interesting thing, the snout width to CBL ratio is significantly greater in the American lion than tigers, lions, and jaguars. Furthermore, the nasal aperture width to CBL is also greater than lions, tiges, and jaguars. For whatever reason, P. atrox needed to breathe at a better rate as indicated by its snout dimensions. The nasal aperture width is an aspect where P. atrox is strikingly similar to P. leo, in my opinion supporting the notion that P. atrox was just as cursorial.

3. Guaging the ratios of P. atrox skull to other bones is a bit difficult. Generally, there is a lot of variance within a species on how the skull relates to the rest of the body. Also, "full skeletons" are often just mixes and matches of different individuals. Females seems to have proportonately smaller skulls, while the largest of the males the opposite. I compared the largest mass estimates of long bones to the closest mass estimate from a skull, and I've found that P. atrox has a proportionately similar sized skull compared to lions, maybe slightly smaller. Though, my lion database is small so take this observation with a grain of salt. Regardless, P. atrox have a significantly proportionately larger skull compared to tigers.

4. No weights have been taken of P. atrox skulls that I know of. As stated in (2), P. atrox has thinner skulls from the arches but a very wide snout. In terms of long bones, they are quiet robust, at the high end of the spectrum, sitting right next to modern lions. 

5. Merriam and Stock (1932) states many digits have been found. From around page 156, they went to an in-depth analyiss of digits. Here's the link:
http://babel.hathitrust.org/cgi/pt?id=md...up;seq=180

I don't really know of studies of the digits of modern cats, any reference could help draw a comparison.

6. Certainly. I tried deriving estimates from a small sample of lions and tigers in the Copenhagen museum, but the correlation isn't so strong as the skull proportionalities are all over the place (partially due to the fact that females have such proportionately small skulls). So I opted to use the larger database of more species. In my opinion, a larger sample size of lion and tigers instead would probably be better than using smaller species in the estimate for the reasons described in my P. s. fossilis post. (7) might help explain the estimation method better.

7. Do you mean in terms of estimating the specimen masses? If so, I used least squares regression to plot the grow trend. To get a linear relationship, I logarithmically scaled mass and bone dimension. Using the line of best fit equation, I predict the mass. Specimens that are out of the modern database limits are fragile to estimate. Have an uneven distribution of large and small estimates leads to awkward estimates, as in the case of Anyonge and even Christiansen and Harris at points. To try to overcome this, I tightened my specimen range to just tigers and lions.

I hope I answered with enough detail. And no worries, I really enjoy these discussions and answering questions.  
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