Ancient Jaguars

[tigerluver]

Please fill in the gaps in my memory, but the largest Pleistocene P. onca specimens are extrapolated from dentition, not skulls. That can mean two things. This cat had disproportionately large dentition for its skull, so dentition overestimated its size. Or, dentition are more common to find than skulls and thus better represent a wider size range within the species/population. 

The mandible fragment is a great find! The M1 is 21.1 mm, so it's right in the range of a modern jaguar. 

The excel file in this post details the dental record of the jaguar. The average M1 lengths are:

Extant P. onca: 20.17 mm (n=15, 17.4-22.5 mm)
P. o. augusta: 23.08 mm (n=14, 20.7-25.4 mm)
Pleistocene South America P. onca: 22.82 mm (n=15, 22-23.5 mm)

Based on isometric scaling between the aforementioned averages, P. o. augusta would be 1.5x the mass (1.144^3) of extant P. onca and Pleistocene South America P. onca would be 1.45x (1.131^3) the mass. Based on my studies of tigers and ancient lions, dentitions scale with positive allometry in comparison to skull length. I'd expect the same trend in jaguars. Therefore, I'd expect the mass difference to be greater as well. Reply