Meeting Abstract

P2.70  Sunday, Jan. 5 15:30  Testing the Accuracy of Skeletochronological Indicators in Age Determination for the Tegu Lizard, Tupinambis merianae BERNARD, M*; CURRY ROGERS, K; Macalester College; Macalester College rogersk@macalester.edu

Growth marks in vertebrate bone tissue indicate periodicity of bone deposition. Lines of arrested growth (LAGs) occur in all major vertebrate groups, and are highly mineralized concentric rings that occur within compact bone and indicate complete cessation of growth. LAGs are thought to represent endogenous responses to particular environmental cues, regardless of metabolic rate. LAGs have been researched most thoroughly in extant amphibians and reptiles, and several studies have corroborated the hypothesis that LAGs represent annual cycles of bone growth that can serve as a proxy for estimating the age of an organism. However, intraskeletal variation in LAG deposition remains poorly understood. Do all skeletal elements from a single animal document the same age as recorded by LAGs? We analyzed a single zoo specimen of Tupinambis merianae that was euthanized at 5 years of age. We sampled six appendicular elements – left humerus, radius, ulna, femur, tibia and fibula. The general histology of slow-growing lamellar-zonal bone with sparse vasculature and endosteal remodeling is characteristic of all elements. However, the number of LAGs varied between the limb bones. Only the fibula accurately records the known age of our sampled skeleton. All other sampled elements record an age of only three years. Our results highlight intraskeletal variation in LAGs that should be considered, particularly in studies of fossil vertebrates, where researchers may only have access to a single element from which to garner skeletochronological data.