Phylogeny of the Cenozoic calcareous nannoplankton genus Helicosphaera

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Abstract
Because the paleontologic concept of Coccolithophoridae species is restricted and far removed from the biologic concept, which itself is not yet satisfactorily established, calcareous nannofossil taxonomy remains in an unsatisfactory state. This situation is clearly reflected by various authors' widely different interpretations of the phylogenetic relationships among species in a given genus and among genera. Examples taken from the extant genus Helicosphaera suggest that because of parallel evolution, delineation of phylogenetic relationships among coccolith morphospecies using morphologic data alone are hazardous, as is delineation of phylogenetic relationships among closely related genera.