Gignac, Paul M.O'Brien, Haley D.Kay, David Ian2025-01-222025-01-222024-07https://hdl.handle.net/20.500.14446/345810Modern mammals and crocodylians both exhibit thecodont dentitions, wherein teeth are implanted in bony sockets in the jaws. These sockets support the dentition by acting as an anchoring attachment for the periodontal ligament. In rodents, it has been shown that alveoli directly cause cusp offset, meaning the jaw is responsible for a critical aspect of tooth crown shape. Despite the apparent importance and variability of this structure, there is a lack of anatomical, evolutionary, and functional work regarding alveoli. I addressed the goal of investigating the evolutionary relationship between alveoli and tooth crowns by establishing alveolar anatomy knowledge, further exploring the alveolar-molar relationship in rodents, and documenting alveolar growth in crocodylians. I used micro-computed tomography (µCT) imaging to generate the high-resolution three-dimensional datasets necessary to visualize and measure the internal skeletal anatomy of alveoli in wet-preserved, frozen, and osteological specimens of extant crocodylians and mammals, analyzing relevant measurements in a phylogenetic context to test hypotheses regarding alveolar anatomy evolution. I find that alveolar anatomy has substantial differences between crocodylians and mammals, with crocodylians exhibiting mammal-like alveoli in the mesial portion of the jaw, and a unique anatomical configuration of a thick layer of bone in the distal portion of the tooth row. In rodents, I find that the tractability of the established alveolar-cusp offset trend is not preserved across ontogeny, unless open root morphology is present to serve as an embryonic anatomical analogue. Looking into a relatively undescribed system, I find that extant crocodylians exhibit positively allometric alveolar trough thickness, and the ontogenetic completion pattern of alveoli in heterodont vs. homodont species is different, suggesting a possible relationship between alveoli and tooth shaping, with functional implications relevant to feeding. Overall, this study finds that alveoli have complex anatomical patterns and relationships with dentitions in extant mammals and crocodylians. Using these conceptual foundations on alveolar evolutionary morphology in mammals and extant crocodylians, I can address evolutionary questions involving the evolution of mammal-grade dentitions in non-mammalian groups using notosuchians as a natural experiment to further elucidate the evolutionary relationship between tooth crowns and their hard tissue support structure.application/pdfCopyright is held by the author who has granted the Oklahoma State University Library the non-exclusive right to share this material in its institutional repository. Contact Digital Library Services at lib-dls@okstate.edu or 405-744-9161 for the permission policy on the use, reproduction or distribution of this material.Dissertationalveolicomparative morphologycrocodyliansdevelopmentevolutionary morphologyteeth