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Show THE UNIVERSITY OF UTAH HONORS COLLEGE EURYPTERID PALEOECOLOGY: CHARACTERIZATION AND ANALYSIS OF A LATE SILURIAN SHALLOW MARINE FOSSIL ASSEMBLAGE FROM SOUTHERN ONTARIO, CANADA Leah Moelling (A.A. Ekdale) Department of Geology and Geophysics University of Utah Eurypterids were giant chelicerate arthropods that have been extinct since the Permian Period. Eurypterids are rare as fossils, and many eurypterid fossils are likely shed skeletons (molts), which makes it problematic w h e n seeking to determine the types of environments in which they lived. Analysis of functional morphology in conjunction with investigations of their paleobiogeography often are employed to study eurypterid paleoecology and paleoen-vironments. A selection of specimens from the Ciurca Collection in Yale University's Peabody Museum of Natural History was examined to determine the composition of the fossil assemblage, state of preservation, and implications for environmental interpretation and community relationships. Specimens are from the Williamsville Formation (Silurian) in Fort Erie, Ontario, Canada. Due to the predominance of microenvironments represented in the Williamsville Formation, a localized environment in a narrow time range was selected to focus the evaluation. Eurypterids include the genera Eurypterus, Pterygotus, Dolichopterus, Buffalopterus, and Paracarcinosoma. Fossil fragments are most common, but nearly complete specimens also are present. Orthocone nautiloids, brachiopods, graptolites, synxiphosurans, phyllocarid crustaceans, Naraoia bertiensis, unidentified gastropods, and the terrestrial plant Cooksonia are also known from this locality, although many of these other organisms are neither abundant nor well preserved. The presence of orthocone nautiloids and prosobranch gastropods implies a marine environment, which is inconsistent with the previously published interpretation of the Williamsville Formation as representing shallow, nearshore brackish to hypersaline environments, such as lagoons. This fossil assemblage may indicate less restricted, more open marine salinity, but the lack of trace fossils in these specimens suggests little or no bottom-dwelling life as a result of low oxygen availability. This evidence may represent unusual conditions in a localized environment. Leah Moelling A. A. Ekdale 229 |
