Palaeontology and stratigraphy of the inoceramid species from the mid-Turonian through upper Middle Coniacian in Japan

Abstract

Upper Cretaceous strata are weIl exposed in many areas of Japan, although good exposures through the Turonian/Coniacian boundary are not common. This paper focuses on six areas in Hokkaido, Shikoku and Kyushu and documents the stratigraphical distributions of inoceramid species. These data are used to summarise the stratigraphical ranges of Turonian/Coniacian taxa in Japan. In part 1 of the paper, 17 species are described, with some biometric data and phylogenetic interpretation. These species are: Inoceramus (Inoceramus) hobetsensis NAGAO & MATSUMOTO, I. (I.) teshioensis NAGAO & MATSUMOTO, I. (I.) iburiensis NAGAO & MATSUMOTO, I. (I.) tenuistriatus NAGAO & MATSUMOTO, I. (I.) pedalionoides NAGAO & MATSUMOTO, I. (I.) lusatiae ANDERT, I. (I.) uwajimensis YEHARA, I. (Cremnoceramus) rotundatus FIEGE, I. (Cr.) ernsti HEINZ, I. (Cr.) deformis MEEK, I. (Cr.) lueckendorfensis TROEGER, I. (Platyceramus) tappuensis nom. nov., I. (Pl.) szaszi NODA & UCHIDA, I. (Volviceramus) koeneni MULLER, Mytiloides incertus (JIMBO), M. mytiloidiformis (TROEGER), and M. sublabiatus (MULLER). In part 2, the stratigraphical distribution and correlation of these species are discussed.