Publications

Although Calyptaulax Cooper 1930 is reported widely in Upper Ordovician (Sandbian–Katian) strata of Laurentian North America, most species are poorly documented. Emphasis on those that are well known, such as C. callirachis Cooper 1953, has led to speculation that only a few species with extensive synonymy lists are present across the continent. In this paper, we revise three species that have been overlooked in previous work or ignored because of inadequate knowledge of the types. We reillustrate the types of C. callicephala (Hall 1847) from the Trenton Group of New York and show that the species also occurs in the Verulam Formation of Ontario. Calyptaulax armata (Ulrich & Delo in Delo 1940) is represented by abundant sclerites in the Bromide Formation of southern Oklahoma, but was misidentified as C. annulata (Raymond 1905) in previous work. Calyptaulax antecavata (Ulrich & Delo in Delo 1940) was described originally from the Kimmswick Formation of Missouri, and we demonstrate that it is also present in the Viola Springs Formation of Oklahoma. A fourth species that occurs above C. antecavata in the Viola Springs Formation is left in open nomenclature. These revisions underscore the largely unrealised potential for trilobite-based zonations and correlation in the Upper Ordovician of Laurentia.