Barremian–Aptian (Early Cretaceous) ammonoids from the Choshi Group, Honshu (Japan)

So far, our knowledge of Barremian and Aptian ammonoid faunas from Japan has been insufficient to allow global correlation and palaeogeographic interpretation. We describe here 11 species of Barremian, and nine of Aptian age, from the Choshi Group in Chiba Prefecture (Choshi Peninsula, Honshu). These include a new genus and species of neocomitid (Neocomitoides minimus), new species of Calliphylloceras (C. tsudai) and Pulchellia (P. minima) from the Barremian, and new species of Neosilesites (N. hagiwarai) and Tropaeum (T. ozakii) of Aptian age. Added to these are five specifically indeterminate taxa from the Choshi Group, and a discussion of the faunal similarity between Choshi and other regions in the world using the Nomura-Simpson Coefficient and the number of genera in common. The new Choshi fauna reveals close ties with assemblages known from the Mediterranean (Tethyan realm).