Estimación de la masa corporal de las especies de osos fósiles y actuales (Ursidae, Tremarctinae) de América del Sur

Abstract

Body mass estimation of extinct and extant South American bears (Ursidae, Tremarctinae).
Precise estimates of body mass in fossil taxa are elementary to paleobiological reconstruction. Using demonstrated
relationships between body mass and anatomical measurements in modern mammals, several authors proposed
prediction equations to estimate the body mass of fossil taxa. We calculate the body mass of extant and fossil
South American bears (Tremarctos ornatus and Arctotherium respectively) applying 61 selected allometric
equations to 19 cranial, dental and postcranial measurements. We also estimate the body mass ranges of the five
Arctotherium species by simple size comparison to size and weight of extant bears. Extrapolating on the basis of
geometric similitude with T. ornatus we further estimated the body mass of Arctotherium in order to know if our
estimations, bias published equations, were feasible. Also we test the prediction equations results with a specimen
of Tremarctos ornatus of known body mass. We found that the best prediction equations for all Arctotherium
species are based on femoral (8 equations) and cranial (one equation) measurements. In turn the best prediction
equations for T. ornatus are based on cranial (one equation), first lower molar (one equation), femoral (two
equations) and humeral measurements (three equations).