Sympatric speciation driving evolution of Late Ordovician brachiopod <i>Zygospira</i> in eastern North America

Abstract The morphology of Zygospira , an early atrypide brachiopod, was analyzed using a multivariate approach. Principal component analysis and discriminant clearly differentiated species as they are currently defined primarily based on differences in shell size ornamentation but not terms overall shape. older modesta able to persist into the late Katian (Richmondian) while smaller other brachiopod lineages mostly went extinct. This may have been possible through niche partitioning because shells found attached filter feeders no larger these associations so far. could represent rare example sympatric speciation preserved fossil record. In future, detailed study spiralia their associated structures provide clues ultimate evolutionary affinities this group relation brachiopods evolving at time.