Abstract

Species of the orthide brachiopod genus Glyptorthis occur as common constituents of Late Ordovician benthic marine faunas, particularly in Laurentia. A phylogenetic analysis of 23 North American species of Glyptorthis was conducted to inform a systematic revision and ascertain evolutionary relationships amongst species. Both discrete and continuous characters, from which character states were determined using statistical methods, were utilized within a maximum parsimony approach. Glyptorthis maquoketensis is recognized as a distinct species of Glyptorthis rather than a subspecies of G. insculpta. Glyptorthis virginica is herein synonymized with G. uniformis. Several species of Glyptorthis became widely distributed via dispersal events during the evolution of the clade. The revised phylogenetic topology provides structure to interpret biogeographical patterns within the genus. For example, Glyptorthis insculpta participated in the Late Ordovician Richmondian Invasion into the Cincinnati Basin. The recovered phylogenetic topology suggests that G. insculpta may have invaded the Cincinnati Basin from a low latitude subtropical region of Laurentia, such as the American mid-Continent.