Siluro-Devonian Scutelluinae (Trilobita) from the Czech Republic: Morphology and classification

Complete exoskeletons of species of eight genera of Siluro-Devonian Scutell uinae show the morphology of the cephalon and thorax, particularly glabella r lobation, the wide inward extent of the doublure, and the development of fulcral processes and sockets, the latter more prominent on the external su rface in stratigraphically younger species. The thorax of ten segments has axial rings with an articulating furrow and halfring as in most trilobites. The differences between the exoskeletons of Scutelluinae and Illaenidae ar e many, and imply anatomical differences. It is considered that Scutelluina e are related to the Ordovician Stygininae, and are to be united with them in Styginidae; a common origin for Styginidae and Illaenidae appears questi onable.