FIORELLI lucas Ernesto
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WATER VAPOR CONDUCTANCE AND EGGSHELL THICKNESS IN DINOSAUR EGGS FROM SANAGASTA, LA RIOJA, ARGENTINA: IMPLICATIONS FOR REPRODUCTIVE STRATEGIES AND BEHAVIOR
RODRIGO SALVADOR; LUCAS FIORELLI
Simposio; 10th Mesozoic Terrestrial Ecosystems Symposium; 2009
The structural and functional properties of the eggshell (such as eggshell thickness and water vapor conductance) alongside parental nesting behavior are the main factors affecting success of the embryo. Dinosaur eggs from Sanagasta, La Rioja, Argentina, show a wide variation in shell thickness (inclusively within individual eggs), therefore this work aims to study shell properties and their relation to thickness, and conductance compared with other works. Moreover, the reproductive strategies and behavior of these dinosaurs is hypothesized. Measures of egg radius, pore density and pore diameter were taken and water vapor conductance (GH2O) was calculated. All values were compared regarding eggshell thickness through statistical tests. The eggs show great intra-specific variability regarding radius and shell thickness. Thus, the eggs have eggshell thickness from less than 2 mm (top portion) to more than 7 mm in the equator and bottomportion. Thick eggshells have greater pore density and pore diameter, while thin ones have greater conductance. GH2O values for the Sanagasta eggs approximates values known for other sauropods and crocodiles, suggesting they nested in holes or mounds; while taphonomic data from the nesting site implies on a hole. The great thickness indicates great mechanical resistance, which could imply on diminished (or lack of) parental care. The high concentration and proximity of egg clutches points towards a gregarious nesting behavior, but it is not possible to infer site-fidelity. Additionally, GH2O is closer to values for megaloolithid eggs (as well as the microstructure of thin eggshells) which can indicate some relationship among them.