Abundance and extinction at the Ordovician/Silurian boundary of the Cincinnati Arch, USA
Zaffos, Andrew Alexander
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This study tests the relationship between fossil abundance and extinction. Samples were collected from the Late Ordovician type-Cincinnatian Series and the earliest Silurian Brassfield Formation of the Cincinnati Arch. The abundance of brachiopod genera and families was assessed with nine different metrics to account for differences across spatial and temporal scale. Each of these metrics was compared to global duration in the fossil record and survivorship across the Ordovician/Silurian boundary. The results indicate that survivors were more abundant than victims, and are further evidence that the Ordovician/Silurian extinction was not accompanied by a macroevolutionary selectivity regime shift. Furthermore, abundances during this interval are not correlated with duration in the fossil record, a finding that is interpreted as further evidence of changing selectivity patterns through time.