Meeting Abstract

P1.211  Saturday, Jan. 4 15:30  Validity of Skeletochronology for Indicating Age and Growth in Egyptian Tortoise, Testudo kleinmanni ZIMMERMAN, S*; CURRY ROGERS, K; Macalester College; Macalester College rogersk@macalester.edu

We assessed the accuracy of skeletochronology in the assessment of age and overall growth dynamics in a known-age skeleton of Testudo kleinmanni (Egyptian Tortoise). Skeletochronology is often utilized in the determination of the minimum age of an individual by enumerating the concentric growth rings within the cross section of a bone that record periodic slowing and/or cessation of growth. These lines of arrested growth (LAGs) are frequently utilized in age determination for fossil vertebrates including dinosaurs, for which other means of aging (e.g., cranial or vertebral suture, tooth replacement, body mass) are unavailable. However, little is understood about intraskeletal variation in LAG deposition and in other measures of growth rate (e.g., bone fiber organization, primary porosity, degree of remodeling). We analyzed a single zoo specimen that was euthanized at 15.0 years of age due to cancer. We sampled portions of the appendicular skeleton from the left side – femur, fibula, tibia, humerus, radius, and ulna. Skeletochronology and growth patterns among the six sampled elements are inconsistent. Some bones (e.g., femur) exhibit highly vascularized woven bone indicative of rapid growth, while others (e.g., tibia) are predominated by lamellar bone, indicative of slower growth. Secondary remodeling also varies, with some bones exhibiting high levels of remodeling (e.g., radius) while others (e.g., fibula) lack remodeling. Similarly, the number of LAGS varies among bones. The humerus and femur both record 4 LAGs, the tibia records 3 LAGs and the other elements record only 2 LAGs. None of the sampled bones accurately record the 15-year age of the specimen. Our results highlight the need for caution when applying skeletochronological methods, particularly among fossil taxa where only single elements are available to study.