REEVALUATION OF A COMMON CALYMENID TRILOBITE FROM SILURIAN CARBONATE DEPOSITS OF SOUTHWESTERN OHIO

Recent studies on lower to middle Silurian stratigraphy in active quarries of southwestern Ohio has resulted in discovery of a moderately diverse trilobite fauna, including some new taxa. Most trilobites are preserved as molds in dolostone, and this preservation style has limited effective comparison to trilobites preserved under other conditions.

The most common trilobite in the Silurian carbonates of Ohio is a species that has been assigned to at least four genera over the past 100 years. Preservation in dolostone tends to obscure some morphologic features and minimize effective comparison with related species. This trilobite has been variously referred to as Calymene celebra, Flexicalyemene celebra, Gravicalymene celebra, and Sthenarocalymene celebra. Multiple generic assignments may have artificially inflated the number of genera reported in literature. Parsimony analysis is being used to help gain insight into the evolutionary affinities of this calymenid species. In addition, specimens are being compared to calymenids preserved in coeval shales units of the Midwest. Calymene, which is known from excellent material in the Waldron Formation of Indiana, appears to be congeneric, if not conspecific, with C. celebra from the dolostone units.