Ancient Jaguars

[KRA123]

(12-21-2020, 09:14 AM)Balam Wrote: @KRA123 I agree with you on the Oregon cave skull, while more information is required to reach a solid conclusion, all decks are on the table as it pertains to that particular specimen. We've seen tremendous overlap with Pa. onca and Pa. atrox remains, so to be cautious from jumping to conclusions is reasonable.
That being said, the opposition in placing P. onca augusta as a different species based on craniometric analysis is not as strong as what has been publicized for Pa. onca mesembrina by Chimento et al. in 2017. Even with the latter, that those remains analysized belong to Pa. atrox remains a contested claim.

In regards to Pa. onca augusta remains, the canine teeth mentioned by me before was posted by the account "Prehisotirc Florida" on Instagram which is run by a curator of fossil remains from the state. The measurements and comparison with Pa. atrox are foud below (credits to epaiva for originally posting this):

*This image is copyright of its original author

*This image is copyright of its original author

More remains for a Pleistocene Pa. onca specimen can be found at fossil action Paleo Enterprise with its respective measurements:

*This image is copyright of its original author

*This image is copyright of its original author

In both cases, the length of the canines puts it in the range of what is seen with extant lions and tigers, with the first fossil representing a particularly large canine.

In terms of scientific data, the first widely available publicized paper on the species comes from Schultz et al (1985), from the University of Nebraska, the paper was titled: A Pleistocene Jaguar from North-Central Nebraska, it goes in-depth about the skull measurements of one particular specimen, thout to belong to a female. The complete dimensions of the skull were not disclosed, but the lengths for points within the skull between the border of the palette and the posterior of the snout are given. I don't really know of similar measures taken for tigers  or lions to compare, but the paper mentions these values as particularly large for an extant jaguar, while on par with different skulls allocate to Pa. onca augusta examined by Schultz previously:

*This image is copyright of its original author

*This image is copyright of its original author

A more recent paper, The large jaguar that lived in the past of México: a forgotten fossil, goes into more detail as it pertains to remains found in Mexico for a Panthera species that shows craniometric proportions of a jaguar, but with much larger proportions. In this case, only a mandible could be studied:

*This image is copyright of its original author

*This image is copyright of its original author

The doubt in placing these remains into Pa. onca is derived from the proportions of the skull, which is why the classification of augusta is put in place as the dentition from these specimens do not show affinity with those of the cave or American lion.

*This image is copyright of its original author

Material: a mandible with molars and canines of a felid of great size, from the Pleistocene in Jalisco, Mexico.

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I would also challenge the idea that Bergmann's rule is actually a scientific theory (i.e. has been proven beyond a reasonable doubt), there's plenty of scientific work publicized which shows that the correlation between the increment of mass in an animal and the latitude in which those species live, is not directly correlated by their proximity to the poles, as it is widely believed. We can discuss this further if you want, but to conclude my position on the topic at hand, there seems to be more than enough data to suggest larger sizes for Pleistocene jaguar forms in North America, baring that the difference in the skulls and dentition of Pa. onca, atrox and spelaea can all be discerned thanks to the abundance of fossil records from the last two.

Check my post #33 in this thread, I posted some information about the UNSM 1,104 skull. It's within the size range of extant jaguars. Definitely Bergmann's rule is controversial, I was just spitballling. Anyway, it is important to determine which modern jaguars the fossil are being compared to when they are described as particularly large. I recently read a study where modern jaguars were compared to Rancholabrean and Irvingtonian specimens, as well as one particularly large South American individual. If I remember correctly, the large modern individual turned out to be larger than both the Rancholabrean and Irvingtonian averages. Also, consider that the Oregon caves page described the 1995 jaguar fossil individual (which apparently has proportions similar to a modern jaguar) as being the same size as young Bengal tigress; well, a huge modern Jaguar like Lopez should also be around the size of a Bengal tigress, right? Unfortunately, I don't have the time to go look for or write about that study right now, so i think we will have to agree to disagree, at least until a later date. Reply