Chairperson, Graduate Committee: Frankie Jackson; David Varricchio (co-chair)Lawver, Daniel RyanFrankie D. Jackson was a co-author of the article, 'A review of the fossil record of turtle reprodution: eggs, embryos, nests, and copulating pairs' in the journal 'Bulletin of the Peabody Museum of Natural History' which is contained within this thesis.Armand H. Rasoamiaramanana and Ingmar Werneburg were co-authors of the article, 'An occurrence of fossil eggs from the Mesozoic of Madagascar and a detailed observation of eggshell microstructure' in the journal 'Journal of vertebrate paleontology' which is contained within this thesis.Frankie D. Jackson was a co-author of the article, 'An accumulation of turtle eggs with embryos from the Campanian (upper Cretaceous) Judith River Formation of Montana' in the journal 'Cretaceous research' which is contained within this thesis.Frankie D. Jackson was a co-author of the article, 'A fossil egg clutch from the stem turtle Meiolania platyceps: implications for the evolution of turtle reproductive biology' in the journal 'Journal of vertebrate paleontology' which is contained within this thesis.2017-12-272017-12-272017https://scholarworks.montana.edu/handle/1/13101Although known from every continent except Antarctica and having a fossil record ranging from the Middle Jurassic to the Pleistocene, fossil turtle eggs are relatively understudied. In this dissertation I describe four fossil specimens, interpret paleoecology and conduct cladistic analyses in order to investigate the evolution of turtle reproduction. Fossil eggshell descriptions primarily involve analysis by scanning electron and polarized light microscopy, as well as cathodoluminescence to determine the degree of diagenetic alteration. Carapace lengths and gas conductance are estimated in order to investigate the ecology of the adults that produced fossil turtle eggs and clutches, as well as their incubation environments, respectively. Cladistic analyses of turtle egg and reproductive characters permit assessment of the usefulness of these characters for determining phylogenetic relationships of fossil specimens and the evolution of reproduction in turtles. Specimens described here include 1) Testudoolithus oosp. from the Late Cretaceous of Madagascar, 2) a clutch of eggs (some containing late stage embryos and at least one exhibiting multilayer eggshell) from the Late Cretaceous Judith River Formation of Montana and named Testudoolithus zelenitskyae oosp. nov., 3) an egg contained within an adult Basilemys nobilis from the Late Cretaceous Kaiparowits Formation of Utah, and 4) a clutch of Meiolania platyceps eggs from the Pleistocene of Lord Howe Island, Australia. Meiolania platyceps eggs are named Testudoolithus lordhowensis oosp. nov. and provide valuable information on the origin of aragonite eggshell composition and nesting behaviors. Cladistic analyses utilizing egg and reproductive characters are rarely performed on taxa outside of Dinosauria. My analyses demonstrate that morphological data produces poorly resolved trees in which only the clades Adocia and Trionychia are resolved and all other turtles form a large polytomy. However, when combined with molecular data, egg and reproductive characters have more resolving potential towards the top of trees. This poor resolution is likely due to homoplasy in the form of character reversals, convergent evolution, and/or from the limited number of informative characters.enTurtlesReproductionFossilsDissertationCopyright 2017 by Daniel Ryan Lawver