Estimating tusk masses in proboscideans: a comprehensive analysis and predictive model

Abstract

ABSTRACTThe size of tusks in proboscideans has numerous implications for their function, biology, ecology, and other aspects of both extant and extinct species. Yet, no prior studies have explored the relationship between the linear dimensions of tusks and their corresponding masses. Here, methods for estimating the masses of proboscidean tusks based on their length and circumference are introduced for the first time. Through extensive regression analysis on a large dataset of tusk dimensions and recorded masses, a robust regression equation was developed. Additionally, it was found that converting tusk volume to kilograms using the cylinder formula yielded highly accurate tusk mass estimates in proboscideans. Also, the potential average tusk sizes of living elephant species under optimal conditions, before the devastating impact of humans, were estimated. The upper incisors of proboscideans remained relatively small until the Late Miocene when tusk sizes comparable to those of living elephants first appeared. Mammoths, along with certain mammutids, stegodonts, and anancines, developed notably larger tusks relative to their body size compared to extant elephants. The largest tusks were identified in derived Plio-Pleistocene proboscideans within Mammuthus, Palaeoloxodon, and Mammutidae clades, with some species bearing tusks weighing above 200 kg per side. World record-sized tusks far surpassed this figure.