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.

The dataset is derived from observations of new taxa and historical documents describing other species of Heterostraci. The matrix of characters and taxa was copied into a text file, translated into NEXUS and TNT files by Mesquite. The example TNT (*.tnt) and PAUP* (*.nex) files include basic commands for replicating the results.

Standard notations are used with '?' meaning no data is available to determine the transition state for the character for this species. A dash indicates that this entry is not applicable as the contingent state was not met in another field. See character lists and descriptions.