Barrick 9507992 The question of whether dinosaurs lacked effective temperature control and were heterotherms or were endothermic homeotherms has important implications for their life histories, evolution, rise to dominance in terrestrial ecosystems, and eventual extinction. A great deal of evidence has been amassed regarding dinosaur endothermy which includes brain size, feeding mechanics, paleobiogeography, posture and gait, behaviors, bone histology and predator/prey relationships (Carroll, 1988; Weishample et al., 1990). These studies have changed the general perception of dinosaurs and they are now thought of as active animals, though considered to be ectothermic or mass homeotherms (Ostrom, 1980). During the initial phase of funding (EAR91-06660), we investigated the application of a new high precision 18O isotopic technique for the analysis of bone phosphate. By using the isotopic difference between core body and extremities and the phosphate paleotemperature equation, realtive body temperature differences can be calculated to determine if an fossil animal was a heterotherm or homeotherm. Of the 13 species of dinosaurs analyzed, all appear to be homeotherms with one Jurassic species exhibiting regional heterothermy. These homeothermic bone isotope patterns cannot be ascribed to diagenetic alteration, because none of the specimens have isotopic equilibrium between the co-existing phases of bone phosphate with structural carbonate or calcite cements (co-existing phase test). This proposal seeks funds to expand our modern bone isotope data base by working with the NCSU School of Veterinary Medicine on 5 modern target species. The species will also propose to expand our fossil data base to complete our survey of different dinosaur clades, and also to search for the origins of homeothermy in therapsids and in a Triassic assemblage from Argentina.
