Date of Award
Bachelor of Science
Amia calva is an icon in the field of comparative osteology, yet we have a poor understanding of the evolution of the genus because many fossil amiid bones have gone unidentified. Here we identify new material of the genus, Amia, with evidence of two unidentified species. Previously, the oldest known material identifiable as Amia cf. A. pattersoni, was a specimen from the Paleocene epoch of Alberta, Canada approximately 58 million years in age. Fossils of the two unidentified species of Amia were found in the Sentinel Butte Formation, a geologic formation of Paleocene age (~ 60 million years ago) near the town of Medora, North Dakota. The specimens are classified as Amia because the coronoid tooth plates exhibit conical teeth and the parasphenoid exhibits a long tooth patch that extends anteriorly past the ascending rami of the bone. This new Amia material is distinguished from other species based on three criteria. First, the parasphenoid tooth patch is extremely wide posteriorly, reaching the lateral margins of the bone, but very long and narrow anteriorly. Second, the gular plate is uniquely shaped, not being truncated posteriorly but rather tapering both anteriorly and posteriorly. Third, the teeth of coronoid tooth plates are robust, unlike those of other species of Amia which are thinner and more elongated. The frontals of each specimen are very different in shape and proportions suggesting two different taxa. Width and length ratios of bones from the Amia specimens were analyzed to further determine fossil characteristics. One of these taxa could attain a large size with a total length well in excess of 1 m. Together, these taxa highlight the necessity to document the evolutionary history of this long and important lineage of Amia.
Moore, Abby Grace, "Earliest Known Material of Amia, Bowfin, From The Sentinel Butte Formation (Paleocene), Medora, North Dakota" (2020). Theses and Dissertations. 383.