Redescription of Szelepis liu, 1981 (Placodermi, Arthrodira), from the Lower Devonian of China

Abstract

The skull roof of the species Szelepis yunnanensis (Liu, 1979) from the Early Devonian of Yunnan is redescribed, as well as other Szelepis material previously published. It appears that only the holotype of S. yunnanensis can be confidently assigned to this genus. The fusion of the preorbital plates into one plate strongly suggests the assignment of Szelepis yunnanensis to the monophyletic family Actinolepididae Gross, 1940, sensu stricto (comprising Actinolepis Agassiz, 1884, and Bollandaspis Schmidt, 1979). This is confirmed by a phylogenetic analysis. Hence, Szelepis constitutes the most ancient occurrence of the family but not the sister group to the remaining members.