Article: The ammonites Crioceratites (Paracrioceras) and Shasticrioceras from the Barremian of southwest Japan
Masaki Matsukawa and Ikuwo Obata
Crioceratites (Paracrioceras) asiaticum, Shasticrioceras nipponicum, Shasticrioceras patricki and S. intermedium sp. nov. are described from Barremian strata of southwest Japan. The occurrence of these ammonites in southern Japan provides important evidence for the existence of a cold water current originating in the Arctic and separating northeast Japan from the Asian continent. The lineage of crioceratids from Japan is discussed. Crioceratites (C.) ishiwarai, C. (Emericiceras) emerici and C. (P.) asiaticum from Japan are interpreted as immigrant species from the Tethyan Sea or their descendants.