Protaspides of Leiostegium and their implications for membership of the order Corynexochida

Abstract

Protaspid morphologies of Leiostegium sp. aff. L. formosum from the Lower Ordovician Garden City Formation, western United States strongly support the inclusion of the Leiostegiina in the Corynexochida. A similar metaprotaspid morphotype is present in the three suborders of the Corynexochida, the Corynexochina, Leiostegiina, and Illaenina, supporting their corynexochid membership.