Ancient Jaguars

[tigerluver]

(04-15-2021, 04:24 AM)Balam Wrote: This study hasn't been posted here but a paper that studied the genetic relationship between extinct Pleistocene Patagonian taxa through phylogenetic reconstructions based on mitochondrial DNA concluded that P. o. mesembrina was well within the genetic markers of P. onca, not P. atrox. The likelihood that Chimento and Agnolin's (2017) paper did in fact relate to P. atrox becomes even less substantiated considering that the genetic data from this species is completely lacking from the area. The cave paintings do not depict lion-like creatures (but they do depict spotted felids), and the remains of P. atrox have not been found in other South American or Central American sites southern from Mexico to infer a proper migration, as we do have with other species. 

Synergistic roles of climate warming and human occupation in Patagonian megafaunal extinctions during the Last Deglaciation, by Metcalf et al (2016):

*This image is copyright of its original author

*This image is copyright of its original author

While the modern jaguar forms a monophyletic species, during the Pleistocene P. o. mesembrina could be genetically distinguished as a different subspecies, but not being different enough to be classified as a distinct species altogether. This is why using craniometric data from modern jaguars to rule out the possibility of P. o. mesembrina belonging to a different species is flawed, as the morphology of P. onca would vary from this other subspecies, and the environmental factors that could've contributed to the greater size on the Pleistocene form (such a larger prey availability and biomass during) are not present in the native ranges of extant jaguars. These ecological differences are key in distinguishing the morphological differences the two subspecies depict.

*This image is copyright of its original author

From the supplementary data:

*This image is copyright of its original author

*This image is copyright of its original author

If we are to take Chimento and Angolin's work with a degree of plausibility, we should also take into consideration other data that points towards the contrary with stronger DNA samples as opposed to ambiguous skull markers. The idea that P. atrox made it as far as the southern tip of the Patagonia is at best very dubious.

Furthermore, I found their work to lose credibility considering the degree of speculation in which they went to describe the supposed appearance of "P. atrox" based on factors that may have not been related at all, such as fur found on the caves which led them to believe it had a "reddish" coating, something that we do not see i the frozen remains of cave lion cubs.

Sorry I got to this so late. Great paper! 

I was comparing the datasets and they are from the same sites mentioned by Chimento and Agnolin (2017). The lack of P. atrox in the same can obviously mean there was no P. atrox or that the frequency of P. atrox was much less and thus it wasn't represented in the small random sample. The sample size is decent at 17.

I could not find it so I was wondering if you were able to find a divergence date between P. onca and P. onca mesembrina in the study? It would be helpful in our reconstructions.

I also have the legends for the excellent comparative photos in Chimento and Agnolin (2017). A is of course the "P. onca mesembrina" skull. B-D is P. leo, E is P. atrox, F and R-Y are extant P. onca, G-H are the fossil P. onca.

Here are the figures again:

*This image is copyright of its original author

*This image is copyright of its original author

From these comparative photos, Chimento and Agnolin (2017) are correct in the assertion that the incisive foramina of the skull in question are visible in superior view. Extant jaguars do not have this trait and would be solid evidence against the mystery skull being of the extant P. onca form. Even in the fossil P. onca we see the incisive foramina are not visible from the superior view. They also assert that the snout is indistinguishable from P. leo/P. atrox. To me, the rostrum looks more stout then pretty much all the other specimens in the photo except maybe P. spelaea (J) and the fossil P. onca (G and H specifically). Stoutness is however a more jaguar-like trait. I will note that the damage to the snout also makes it harder to ascertain the true stoutness of the rostrum.

It could be fair to say the skull does not group well with comparative specimens as its traits are a unique combination. If "P. onca mesembrina" is a genetically distinct taxon related to extant P. onca, this could make sense. I also want to highlight a new species of P. balamoides in this discussion. To quote, "Panthera balamoides sp. nov. combines characters of smilodontids and Panthera, with more similarities to Panthera onca." This asks the question if the "P. onca mesembrina" skull and P. balamoides are of the same species. Reply