PHYLOGENETIC AND TAXONOMIC REVISION OF CERAURID TRILOBITES

The genus Ceraurus Green 1835 is a speciose group of cheirurid trilobites from the Ordovician of North America. Despite being diverse and successful throughout the Late Ordovician, the group went extinct at the end Ordovician Mass Extinction Event. Over the years, taxonomists have split this large genus into various genera (Leviceraurus Hessin 1988, Gabricerarus Prybl Vanek and Pek 1985, Bufoceraurus Hessin 1988, etc.) suggesting “Ceraurus” might actually be better considered a tribe of related forms, however this hypothesis has not previously been tested phylogenetically. This study used specimen based phylogenetic analysis in order to elucidate the relationships between species within this potential “ceraurid tribe”. To this end, a larger scale phylogenetic analysis was first conducted on the subfamily containing the ceraurids, the Cheirurinae Hawle and Corda 1947, in order to understand the positions of the groups within the clade. Then, small phylogenies were conducted on the various clades of ceraurids in order to understand interspecific relationships, as well as to test the monophyly of the genera. Furthermore, new material collected from Wisconsin, Iowa, Missouri, New York, and Ontario were used to name several new species of ceraurid trilobites, as well as to revise established taxa, including the type species of the genus, Ceraurus pleurexanthemus Green 1835. This revision of the ceraurids is part of a larger, ongoing study of cheirurid trilobites that seeks to both revise the taxonomy of the cheirurids, as well as to generate phylogenetic hypotheses that can be used to better understand the macroevolutionary significance of the End Ordovician Mass Extinction on the evolution of the group as a whole.