Ancient Jaguars

[tigerluver]

Absolutely excellent post @Balam.

To open, I think we have been aware that dentition are very poor predictors. The issue we have at hand is that it is all we have for these ancient jaguars and as @KRA123 noted the skulls we have been able to pinpoint don't show animals larger than extant jaguars. As such, we have to look at the dentition which have the larger specimens. A quick note, the formulas above are isometric (scale factor of 3). We couldn't check for allometry as the data is no available. I could use my tiger data as a model for the scale factor but when a skull I measured of ~380 mm had an M1 smaller than a female's, you can imagine how useless I'd find the regression.

On IGM 9518: Good note that the canine is larger. However, we cannot choose the canine over the M1 and vice versa in terms of which is the better predictor. From that nice table, both of their R^2 are poor with only a mild correlation. However, measurements of the actual mandibular ramus itself are quite strong in correlation to mandible length, and by extension skull length. I really wish I had some of my own jaguar data but I only measured lion and tiger skulls for a while now and missed out. So I'll open up Merriam and Stock (1932). So we have the height at M1 for IGM 9518 which is 31.2 mm. This seems to be smaller than most of the males in Merriam and Stock (1932). We can't exactly compare the other ramus height measurement as for IGM 9518 it's taken at the p3, while Merriam and Stock (1932) measured at the p4. The p3 height is generally greater than the p4, so as such the anterior height of the mandible is also smaller than the male extant jaguars in Merriam and Stock (1932). To be frank, this shows that IGM 9518 had disproportionately large dentition and also reemphasizes how poor dentition are at predicting size.

One last thing, I still haven't identified this source. Anyone know?:

*This image is copyright of its original author

Will have to get the other discussion points later. Reply