Palaeogeographic distribution and diversity of cephalopods during the Cambrian–Ordovician transition

Abstract Since the early 20th Century, when the first cephalopods from late Cambrian strata were discovered in North China, more than 160 species belonging to 39 genera in nine families and five orders, have been described from both North and South China, together with North America, Siberia and Kazakhstan. We compiled and analysed all published Cambrian cephalopod occurrences in these regions: the results show that the oldest undisputed cephalopods are from the Jiangshanian Stage of North China. After their origination, cephalopods reached their first diversity peak in the late Cambrian Acaroceras – Sinoeremoceras Biozone (early Stage 10). This initial diversity peak was followed by the “late Trempealeauan Eclipse”, which eradicated nearly 95% of late Cambrian genera. The extinction event coincides with similar extinctions of trilobites and some other groups of marine life. The rapid subsequent diversification of cephalopods during the Tremadocian (Early Ordovician) was paralleled by a diversification of graptoloids and radiolarians.