Meeting Abstract

90.7  Wednesday, Jan. 7  ONTOGENETIC ALLOMETRY OF LONG BONES IN MAMMALS AND DINOSAURS AND ITS USE AS A PREDICTOR OF LIFE HISTORY TRAITS KILBOURNE, BM; University of Chicago bmkilbou@uchicago.edu

In addition to providing insight into the ontogenetic development of the locomotor system, ontogenetic limb bone allometry may reflect other aspects of an organism’s life history, such as adult and neonatal body mass or growth rate. Similar patterns in ontogenetic long bone allometry in extinct and extant taxa may be useful for inferring life history parameters in extinct taxa. To investigate trends in ontogenetic allometry in biomechancially/functionally similar taxa, femoral allometry was assessed in 23 non-avian dinosaur and 24 terrestrial mammal species. Isometric growth is the most common pattern of growth in dinosaur and mammalian femora. Non-avian theropods have a distinct pattern of femoral growth with little to no overlap with mammals and non-theropod dinosaurs. To examine how ontogenetic allometry varies with life history parameters in mammals, regressions were calculated between femoral allometry and the following life history traits: adult and neonatal body mass, ontogenetic range of body mass, and growth rate. Regressions between femoral allometry and all of the above life history traits were statistically significant, but the majority of the variance in femoral allometry was explained by growth rate. Mammal taxa with high growth rates possess femora that grow isometrically, whereas taxa with lower growth rates have femora that become more gracile during ontogeny. Overall, changes in body mass influence changes in limb bone proportions during mammal ontogeny. Non-avian dinosaurs lack correlation between maximum estimated growth rate and femoral allometry. Caution is warranted when inferring life history traits from long bone allometry in dinosaurs. Future work should be performed on extant birds for a phylogenetic perspective on the allometry of long bones in non-avian dinosaurs.