Background. The estimation of body mass of long extinct species of the family Felidae has been a focus of paleontology. However, most utilized methods impose expected proportions on the fossil specimens being estimated, resulting in a high chance of underestimation or overestimation. This study proposes a new method of estimating felid body mass by accounting for osteological proportionality differences between the extinct taxa being estimated and the living species being used as comparisons.
Method. Using a manipulation of the cube law, 36 equations were formulated that estimate body mass based on certain humeral and femoral dimensions. The formulated equations were used to examine whether the mass of living comparison species, namely the tiger (Panthera tigris), the lion (Panthera leo), and the jaguar (Panthera onca), depends equally on a select set of long bone dimensions. The body mass of five extinct felids, namely Panthera atrox, Panthera spelaea, Panthera tigris soloensis, Smilodon populator, and Smilodon fatalis, was also estimated.
Results. Living comparisons species were found to somewhat incorrectly estimate other living comparison species. All five extinct taxa were found to weigh well over 300 kg, with the largest of the species weighing nearly 500 kg.
Discussion. The inability of one living comparison species to predict the mass of another with strong accuracy suggests that bone dimensions do not solely influence body mass. Discrepancies between the masses of Smilodon populator and Smilodon fatalis were likely the product of the difference in available niches in late Pleistocene North and South America. The masses of Panthera spelaea and Panthera atrox indicate a discrepancy in sociality between the two closely related species. Lastly, the extreme body mass of Panthera tigris soloensis points to great plasticity within the tiger lineage in terms of size, indicating that such variations among tiger populations may not warrant subspeciation.