The last pteraspids (Agnatha, Heterostraci): New material from the Middle Devonian of Alberta and Idaho

This report documents the last pteraspids, (armored, jawless members of the Heterostraci), which are otherwise only known from the Early Devonian of the Old Red Sandstone Continent. Tuberculate pteraspid heterostracans are described from the Middle Devonian beds of two formations in western North America. The late Givetian Yahatinda Formation of Alberta and British Columbia consists of channels cut into lower Paleozoic rocks and represents deposition in marine to littoral environments. Clavulaspis finis new genus new combination, is redescribed from additional material from the Yahatinda Formation and renamed, as the original genus name has proved to be invalid.  The Eifelian Spring Mountain beds of Idaho consist of a large channel that represents a clastic dominated estuarine environment. It contains Scutellaspis wilsoni new genus new species, and the previously described species from the Spring Mountain beds is redescribed as Ecphymaspis idahoensis new genus new combination, prompted by new material and a review of the validity of the original genus name. Phylogenetic analysis shows that these three new taxa form part of the derived clade Protaspididae.