Article: Taxonomy and phylogeny of Staurograptus Emmons from the base of the Ordovician

Taxonomic and biostratigraphic investigation of Staurograptus at small sampling intervals from the basal Ordovician sections at Green Point, western Newfoundland, Riviere Petite Blanche on the Gaspe Peninsula, Quebec, and Wuning in north-west Jiangxi, South China, reveal a complete morphological series comprising three distinct staurograptid forms identified as three species: Staurograptus dichotomus Emmons, S. apertus Ruedemann and S. hyperboreus (Obut and Sobolevskaya). This new discovery suggests a complete phylogenetic lineage for Staurograptus, which is supposedly derived from an unknown dictyonemid form, and is expressed as phased distalward migration of the second-order branches. Descriptions of these three species, reviews of their nomenclatorial histories, evaluations of their distinctive morphological criteria and discussions of their synonymous species or subspecies are presented.