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.