Body mass estimates in extinct mammals from limb bone dimensions: the case of North American hyaenodontids

The body mass estimation of several Limb bone dimensions (shaft cross-sectional properties, articular sizes, and bone lengths) were examined using bivariate Linear regression analyses. The sample included taxonomically and behaviourally diverse small to medium-sized Recent carnivorans and carnivorous marsupials. All examined limb bone dimensions indicated low errors (percentage standard error of estimate, 8-13) for the body mass estimations. Among them, humeral and femoral shaft properties correlated best with body weight, while limb bone lengths gave larger errors. Both humeral and femoral head dimensions have relatively large individual variations, and distal humeral articular dimensions seem to be influenced more by phylogenetic differences. The regressions based on each locomotor group gave slightly lower errors than those based on the total pooled sample. The results were then applied to hyaenodontid creodonts from the Eocene-Oligocene of North America. The estimated body masses (kg) are: Arfia, 5.4-9.5; Prototomus, <6.0; Pyrocyon, 2.6; Sinopa, 1.3-1.4; Tritemnodon, 7.6-13; Prolimnocyon, 1.6; Thinocyon, 0.7-2.5; Machaeroides, 12; Limnocyon, 7.8-16; Hyaenodon, 9.1-43. The various Limb bone dimensions give different body mass values, but the variation in estimates is smaller compared to those derived from dental or cranial measurements.