The Lower and Middle Ordovician Cephalopod Faunas of England and Wales

ABSTRACT The cephalopods of the Lower and Middle Ordovician of England and Wales are described and referred to twenty-four taxa across sixteen genera, of which six (Castelloceras, Cyclorangeroceras, Moridunoceras, Saloceras, Sacerdosoceras and Semiannuloceras) are new. Twelve named species are described, five of which (Castelloceras arennigense, Cyclorangeroceras blakei, Moridunoceras castelli, Sacerdosoceras promus and Semiannuloceras abbeyense) are new. As a consequence of small sample sizes and poor preservation, the remaining species are treated in open nomenclature. Two new families (Polymeridae and Rangeroceratidae) are proposed. The fauna contains members of the Orthoceratoidea that are earlier than those described from other parts of the world and throw light on the early development of this group.