Stable oxygen and carbon isotope analyses of extinct archosaurs (Dinosauria) and their closest extant relatives, ratite birds and crocodylians

Stable oxygen (from phosphate, delta18O p, and carbonate, delta18Oc) and carbon (delta13C) isotope analysis can provide physiological, climatological, ecological, and dietary information about fossil vertebrates, most commonly for fossil mammals, but less commonly in older extinct non-avian dinosaurs. This is due to greater physiological and ecological variation between extinct archosaurs and their extant relatives (birds and crocodylians) than between extinct mammals and their extant relatives. Diagenetic alteration is also more likely in older specimens. I attempt to mitigate these challenges and use stable isotopes to determine physiological, ecological, and dietary information for extinct non-avian dinosaurs.; In Chapter 1, I micro-sample enamel from multiple teeth from dental batteries of an ontogenetic series of Maastrichtian Edmontosaurus specimens, and compare them to extant archosaur data. Results suggest that while absolute enamel delta18Oc values may be altered, the pattern of seasonal cycles is preserved and provides information on tooth mineralization times, rates, and seasons, and dietary information.; In Chapter 2, I develop a delta18O and delta 13C isotopic dataset from extant archosaur (crocodylian and ratite bird) bone, dentine, and enamel and evaluate its potential as an interpretive tool for fossil archosaur biomineral data. Data interpretations address diet, thermoregulatory strategies, behavior, climatic influences, biomineral type, and potential for identifying diagenesis in fossils. delta18O values are explained primarily by local amount of precipitation, dietary sources, water usage, behavior, and habitat, and provide a potential test for diagenesis and evaluation of thermoregulation in extinct archosaurs. Extant archosaur delta 13C ranges generally reflect known dietary patterns in these taxa.; In Chapter 3 I present delta18Op, delta 18Oc, and delta13C data from bone, dentine, and enamel from two North American Late Cretaceous bonebeds, and compare these data to the Chapter 2 extant archosaur dataset. I evaluate diagenesis, and use unaltered values to obtain physiological, dietary, and/or environmental information about bonebed taxa. Unaltered enamel isotopes (Albertosaurus and tyrannosaurid) indicate that theropods retained some similarities to the thermoregulatory system of crocodylians, versus strict endothermy like extant birds. Carbon isotopes have been altered. I describe a method for determining the temperature of biomineralization in terrestrial vertebrates, and address variation in paleoclimate between the two bonebeds.