ESTIMATING ALLIGATOR BODY SIZE BASED ON SKELETAL REMAINS, WITH APPLICATION TO THE GRAY FOSSIL SITE

Body size is associated with nearly every aspect of an organism’s biology, and estimation of size in extinct animals is regularly used to characterize their life histories. Prior studies have examined correlation of total body length (TL) to skeletal measurements in the American alligator (Alligator mississippiensis), with some measurements being better predictors of total length than others. Femur length (FL) has been found to be tightly correlated with total body length in A. mississippiensis, and this relationship has often been used to estimate the body size of extinct crocodilians. In this study, we examine correlations of other limb elements (humerus, radius, ulna, and tibia) with TL in A. mississippiensis and their utility for body size estimation of extinct crocodilians. This new methodological approach will facilitate total length estimation for extinct crocodilians known from only fragmentary remains. As a case study, we estimate the body size of Alligator from the Gray Fossil Site (GFS), an early Pliocene sinkhole lake deposit in the southern Appalachians of northeastern Tennessee. Results suggest that the GFS Alligator is smaller on average than modern A. mississippiensis. A relatively smaller size in the GFS Alligator could reflect phyletic size differences between the extant and extinct form, inadequate sampling of the GFS fossil record, or phenotypic plasticity related to environmental conditions and/or food availability.