Ancient Jaguars

[Balam]

(06-27-2020, 06:43 AM)tigerluver Wrote:

(06-27-2020, 05:45 AM)OncaAtrox Wrote:

(06-27-2020, 05:29 AM)tigerluver Wrote:

(06-27-2020, 04:09 AM)GuateGojira Wrote: I am interesting in check the data that they used to calculate those huge weights for Panthera onca mesembrina, because the data that I have do not support that. This is the data that I have at hand about that population, compared with modern jaguars and the giant Panthera onca augusta:

*This image is copyright of its original author

*This image is copyright of its original author

*This image is copyright of its original author

*This image is copyright of its original author

Although I don't have the real size of this large skull, using the scale bar in the first picture I calculare a greatest lenngth of a little over 32 cm. However, when I use the other pictures, I obtain 34 cm and 33.5 cm respectively. With this wide variation in length (32 - 34 cm), I don't dare to state a length from this skull. I am still searching the original document, but I only know that this specimen came from Talara, Peru.

I have attached the P. o. mesembrina dataset. That mass is from a 30.2 mm long (AP measurement) M1. Here's the caveat, all other fossil P. onca M1 they have recorded are quite a bit smaller and more in the range of a jaguar. They used this fact as support that "P. o. mesembrina" is actually P. atrox. In my opinion, the statistics support that idea too and this is P. atrox, not P. onca.:

*This image is copyright of its original author

Also, what is the source of those excerpts? Thanks.

I have issues believing those remains belong to P.atrox due to de lack of fossil evidence found in the northern part of the Andes or South America for that matter, in the article they described an illustration found at cave of jaguar-like creature they used to determine the aspect of P.atrox. While not impossible, I see it much more plausible that those illustrations were depicting true jaguars and hence the resemblance:

*This image is copyright of its original author

If P.atrox is a true descendant of P.speleae and we know for a fact the cave lion had a very similar coat to that of extant lions, I don't see how P.atrox would then evolve jaguar-style roses, especially when it lived in a grassland environment where a plain light coat would've made more sense.

Reasonable points. Before we discuss further, let's make sure everyone has seen the cave painting:

*This image is copyright of its original author

To start, the reference to artwork is weak, agreed. For one, a 1.5 m cat is small for a giant lion. Jaguars can however attain these body lengths. The authors use of this point to support the presence of P. atrox is weak. However, why does the presence of a jaguar painting on a rock have to exclude the presence of another cat? We have at the least the puma and Smilodon. If we take the art literally, the puma and Smilodon never happened.

Next, a bit of conjecture and theory. We know P. spelaea and P. atrox may have overlapped ranges, indicating they did not interbreed. We also know P. atrox is primitive in form like P. fossilis (Sotnikova and Foronova 2014). Perhaps the rosettes on lion cubs represent a primitive form, and thus P. atrox had rosettes. This could explain the reproductive isolation between P. spelaea and P. atrox despite sympatry. Nonetheless, this is conjecture. To be frank, that cave art doesn't show rosettes either, just dots. Probably simplified rosettes of course, but one can hope for a South American Miracinonyx.

Back to concrete data. If we stick with the reddish-brown un-patterned fur of the cave lions as the skin of P. atrox, we have evidence for that too:

*This image is copyright of its original author

We know the jaguar doesn't have fur like that. The puma may. However, it seems Chimento and Argolin (2017) insinuate that the fur was found in association with the large remains of "F. o. mesembrina". The skull seems to be over 300 mm and of course, not puma-like, removing the puma as the owner of the fur. That leaves Smilodon as the other candidate but for the same reasons this doesn't check out.

On the point of the fossil evidence, a lack of a fossil record certainly shouldn't exclude the presence of a species, especially in warmer regions. The majority of extant species aren't recorded on fossil record for much of their range. Moreover, P. atrox was already found as far south as the Chiapas. What would stop it from continuing onward toward South America? The distance from La Brea to Chiapas isn't much difference from the distance of Chiapas to Cueva del Milodón.

The main critique of Chimento and Argolin (2017) was per Barnett's own work, he found no DNA of fossil lions. However, Barnett didn't sample "F. o. mesembrina" (no fault on him, the specimen is missing). With the small samples sizes that plague paleontology, it's a hefty jump to conclude the lack of evidence in one dataset overrides the evidence in another.

Really good points, especially pointing out the possible retention of the rosettes by P.atrox into adulthood as a form of primitive trait. However, I'm still skeptical of it due to the environment it lived in, even if we take P.fossilis as the basal species for P.atrox, the cave painting in Europe of cave lions could very easily belong to fossilis as well not necessarily only spelaea, and in that sense, those felids were not described with spots or rosettes, hence why I don't see how P.atrox could have later developed the rosettes when it lived in a open and snowy habitat where a white-tawny coat similar to those found of P.spelea would've made more sense. 

As for their expansion into South America, I think if they indeed were able to go beyond Mexico in their expansion, we should in theory have no issues finding remains on different sites across Central America, especially since these lions were so big and potentially could've lived in groups. We do have fossil evidence of Smilodon across all of South America and Central America, so what would make atrox so elusive to find in terms of remains?

The fur is definitely more tricky, the researches did link it to the remains of the fossils of the felid found at the cave but what if such remains are related to a prey item that had been dragged for consumption in such cave, or was another unrelated animal together? While I don't have too much of an established opinion on the fur, I don't find it to be strong evidence for the existence of atrox in the Patagonia.

It personally seems more plausible to me that the remains in the cave for the skull and skeletons are in fact those of P.o.mesembrina and the fur got mixed into it from a different animal that could have or not had contact with said mesembrina specimen. In fact, the possibility of that fur belonging to a Mylodon or even Smilodon seems more plausible to me. But truly for now we can only speculate. Reply