Meeting Abstract
Fossil shark teeth serve as biological proxies for numerous environmental and climatic variables but, geochemical records are not often correlated to ecological factors. For example, the oxygen isotope composition of shark enameloid (δ18O) acts as an indicator of water temperature and salinity. In addition, tooth crown height correlates to body size and the vast number of fossil teeth in museum collections can be used to provide estimates of body size distributions for extinct populations. Changes in body size distributions over space and time are, in part, a consequence of changes to shark life history in response to shifting environmental conditions. We determined body size and δ18O values for Eocene Sand Tigers (Striatolamia macrota syn. Carcharias macrota) from two high latitude (Arctic and Southern Ocean) and two mid-latitude (Gulf of Mexico) localities to compare the effects of latitude, temperature, and salinity on life history. We found significant differences in body size distributions across sites differing in environmental conditions as well as function, as some locations are suggested nurseries. We created a demographic population model to evaluate how temperature likely constrained growth and reproduction of a population straddled between spatially separate nursery and adult sites. By comparing the body size distributions of empirical fossil data with results from our demographic model, we are poised to assess the role of environmental plasticity in the long term evolutionary success of Sand Tigers.
