Many genera are found in Lower Devonian marine deposits of the United States, especially of Utah and Wyoming. Others are found in Lower Devonian marine strata of Europe, especially of
Svalbard,
Norway, and
Podolia,
Ukraine.
Protaspis This genus is known from several species from the Early Devonian-aged Beartooth Butte Formation strata of Wyoming and Utah.
Europrotaspis,
Cosmaspis,
Lampraspis,
Gigantaspis,
Eucyclaspis, and
Cyrtaspidithchys have been formerly placed within
Protaspis as subgenera, or otherwise have been treated as species therein.
Europrotaspis Species of this genus are very similar to those of
Protaspis, but, are found in Early Devonian-aged strata of Western Europe and Podolia, Ukraine.
Eucyclaspis Species of
Eucyclaspis are found in marine strata of the Water Canyon Formation, in Lower Devonian Utah. This genus differs from
Protaspis by having unique processes emanating behind the eye on the orbital plate.
Cosmaspis Cosmaspis is restricted to marine environments of Early Devonian Wyoming and possibly Utah, where it coexisted with species of
Protaspis,
Lampraspis,
Eucyclaspis,
Oreaspis and
Cyrtaspidichthys.
Lampraspis Lampraspis is known from Early Devonian-aged marine environments of Utah and Wyoming. It is closely related to
Oreaspis and
Psephaspis, and the three genera were, at one time, placed together in a subfamily, "Oreaspidinae."
Xylaspis This
Spitzbergen protaspid was originally named
Spitsbergaspis, but that name was discovered to be preoccupied by an Ordovician trilobite. It is similar in form and related to
Zascinaspis and
Woodfjordaspis.
Zascinaspis Species of
Zascinaspis are found in Early Devonian marine strata of Spitzbergen, and are similar in form to
Xylaspis,
Woodfjordaspis and
Gigantaspis, the former two genera being closely related.
Woodfjordaspis Woodfjordaspis is known from an incomplete, partially articulated armor found in early Devonian-aged marine strata of Spitzbergen. It is similar in form and is closely related to
Zascinaspis and
Xylaspis.
Pirumaspis This protaspid is from the Sevy Dolomite Fauna of Late Emsian-aged marine strata in Nevada, where it coexisted sympatrically with
Tuberculaspis, and the protopteraspidid
Lamiaspis. ==References==