BIOMETRY OF THE LATE CAMBRIAN TRILOBITE GENUS DIKELOCEPHALUS AND ITS IMPLICATIONS FOR TRILOBITE SYSTEMATICS

It has been proposed previously that the northern Mississippi Valley S unwaptan trilobite genus Dikelocephalus comprises 26 species. Morphome tric analyses demonstrate that many of the criteria that had been used to define species of Dikelocephalus are invalid and additional analys is of biostratigraphically and biogeographically constrained collectio ns is necessary before the taxonomic status of Dikelocephalus can be f ully resolved. Our results indicate that infrageneric morphological va riation in Dikelocephalus is continuous and lacks gaps that could be t he basis for establishing multiple species. Many of the characters sho wn to be taxonomically insignificant in Dikelocephalus are also widely used in the definition of other trilobite taxa. This suggests that th e species-level taxonomy of many trilobites may be substantially overs plit. Recognition of widespread oversplitting will have important cons equences for biostratigraphic zonations, paleogeographic distributions , and estimates of taxonomic diversity.