Ancient Jaguars

[tigerluver]

I will try to get some clarification on that figure in the future.

For now, I've looked in Merriam and Stock (1932) and Mazak and Christiansen datasets (2011). The skulls in the latter have CBLs of 219.8-229.7 mm. The issue with the jaguar data from Merriam and Stock is that there is an extremely poor relationship between skull length and M1s (see pages 200-204). The largest skulls generally have M1s about the same length as the smaller skulls. Correlating the datasets, an M1 of the skulls in Mazak and Christiansen (2011) was probably around 18-20 mm. These specimens weighed 47.3-67.4 kg. If we take the high end of the skull length to M1 ratio and apply the multipliers in post #46, the average weight for P. o. augusta is (67.4 kg * 1.5) 101.1 kg. The largest specimen (M1 25.4 mm) would be 189 kg estimated very (and perhaps too) generously ((25.4 mm/18 mm)^3 * 67.4 kg). Pleistocene South American P. onca would have an average mass of (67.4 kg * 1.45) 97.73 kg. The largest specimen (M1 23.5 mm) would have weighed 150 kg ((23.5 mm/18 mm)^3 * 67.4 kg). The same generosity is applied here.

By the above analysis, @KRA123 is right these jaguars weren't really larger than the largest Pantanal specimens perhaps. Older literature has the issue of having small specimens represent extant taxa. These specimens are often below the average of the species. As such, often it is said extinct taxa are heftily larger than extant relatives, however this ends up not holding true as the comparative material was from smaller individuals. I could have missed the mark somewhat if the relationships had some allometry but unfortunately we don't have enough data available to run a regression. Moreover, more archaic cats generally had disproportionately large dentition. If this also applied to Pleistocene jaguars, then the estimates are probably inflated. The estimations may also be inflated just because I used the heaviest skull to m1 length ratio I could calculate.

If we compare the M1 of "P. o. mesembrina" to the average Pleistocene South American P. onca, the mass difference would be 2.3x ((30.2/22.82)^3). That seems much too out of the range for the jaguar populations. In extant cats, even the most exceptional of males are not over twice the weight of the average. Rereading Chimento and Agnolin (2017) (Wow, it has already been over three years since this was published...), pretty much all the "P. o. mesembrina" specimens are well out of the range of jaguars. Now I digress, but this would likely mean the lion made it to every continent except Australia and Antarctica, absolutely breathtaking. Reply