Data from: Abundance and extinction in Ordovician-Silurian brachiopods, Cincinnati Arch, Ohio and Kentucky

A basic hypothesis in extinction theory predicts that more abundant taxa
have an evolutionary advantage over less abundant taxa, which should
manifest as increased survivorship during major extinction events and
longer fossil-record durations. Despite this, various paleontologic
studies have found conflicting patterns, indicating a more complex
relationship between abundance and extinction in the geologic past. This
study tests the relationship between abundance and extinction among
brachiopod genera within seven third-order depositional sequences spanning
the Late Ordovician to Early Silurian (Katian-Aeronian) of the Cincinnati
Arch, USA. Contrary to predictions, abundance is not positively correlated
with duration in this study. Abundance and duration range from strongly
negatively correlated to uncorrelated depending on the spatial scale of
analysis and the geologic intervals included, but never indicate that
abundance is an evolutionary advantage. In contrast, abundance was an
advantageous trait prior to the Ordovician/Silurian extinction, and
brachiopods with higher abundances were more likely to survive the event
than less abundant brachiopods. While this result is in keeping with
common models of extinction, it has not been observed previously at a mass
extinction boundary. This may be further evidence that the
Ordovician/Silurian extinction was not accompanied by a shift in the
macroevolutionary selectivity regime.