Orthoconic cephalopods and associated fauna from the late Ordovician Soom Shale Lagersta¨tte, South Africa

ABSTRACT. Orthoconic cephalopods from the Soom Shale Member (Ashgill) are exceptionally preserved and are colonized by lingulate brachiopods and cornulitids. Other fossils commonly associated with orthocones include myodocopid ostracodes and chitinozoans. Size distribution analysis of the brachiopods on one orthocone indicates that it was colonized in vivo. Four orthocone radulae are preserved extending the record of these structures 50 My back to the late Ordovician. Orthocone radula configuration is more similar to that of ammonoids and coleoids than to that of nautiloids.