Some of the inoceramid specimens from the upper Turonian to lower middle Coniacian of the Obira and Ikushunbetsu areas, Hokkaido, are identical or well comparable with certain species, viz, Inoceramus (I.) Iusatiae Andert, I. (Volviceramus) koeneni Muller, I. (Cremnoceramus) deformis Meek, I. (Cr.) ernsti Heinz and I. (Cr.) lueckendorfensis Troger, all of which are cosmopolitan species that, however, have not been recorded in Japan. In this paper, I describe these specimens, subject them to some biometric analyses, and discuss their phylogeny and taxonomic position. Some specimens show intermediate, or transitional characters between Inoceramus and Cremnoceramus, Cremnoceramus and Cordiceramus, and Cordiceramus and Volviceramus, suggesting their phylogenetic relationships. The probable succession for the concerned taxa is preliminarily discussed and the taxonomic ranking of Inoceramus, Cremnoceramus and Volviceramus is also discussed. The above taxa are here regarded as subgenera of Inoceramus. Meanwhile, the widespread occurrence of these species in East Asia has application to international correlation and elucidation of paleobiogeography in the upper Turonian to lower middle Coniacian. In Part 1, I. (I.) lusatiae and I. (V.) koeneni are described and discussed.
Described along with phylogenetic and taxonomic considerations are three species of Inoceramus (Cremnoceramus) from the Upper Turonian to lower middle Coniacian of the Obira and Ikushunbetsu areas of Hokkaido : Inoceramus (Cremnoceramus) deformis Meek, I. (Cr.) ernsti Heinz and I. (Cr.) lueckendorfensis Troger. Concluding remarks on the significance of occurrence of cosmopolitan species (including two species described in part 1) from Japan are also made.
The latest Permian ammonoids, Paratirolites compressus sp. nov. and P. sp., are described from the Permian strata in the Ofunato district of the Southern Kitakami Massif, Northeast Japan. This is the first record of Late Permian fossils from the Ofunato district.
Mesodermochelys undulatus, a new genus and species, is described as the best Mesozoic representative of the Dermochelyidae (order Testudines, superfamily Chelonioidea). This new taxon is described from 15 specimens which include cranial fragments, lower jaw, axial and appendicular skeleton, and a nearly complete shell. These specimens were collected from the Lower Maastrichtian, Upper Cretaceous of Hobetsu-cho, Central Hokkaido, North Japan. Mesodermochelys shares with Cenozoic dermochelyids such derived characters as the reduced processus trochlearis oticum formed by prootic, the anterior process of surangular, and the elongate anterior projection of lateral process of humerus. The scute sulci of Mesodermochelys are nearly absent, only remaining in the neural region of the carapace. The bony shell of Mesodermochelys is well developed as a primitive condition. Some characters such as the unique configuration of the lower triturating surface with isolated simphyseal and lingual ridges, the undulating medial margin of broad peripherals, the narrow neurals, and the elongate iliac blade with outward curvature are considered as autapomorphic conditions of Mesodermochelys. Frequent occurrence of this primitive dermochelyid in the Upper Cretaceous of Japan suggests endemic distribution among Mesozoic chelonioid species.
Thirty-seven species belonging to 16 genera of fusulinaceans are discriminated from the Akuda and Horikoshitoge Formations, exposed in Hachiman town, Gifu Prefecture, Central Japan. Among them, the following six species are newly proposed : Sphaerulina akudensis, Dunbarula uenoi, Schwagerina shukoae, S. kanumai, Pseudofusulina minoensis, and P. miyamensis. This fusulinacean fauna is similar in composition to that described from the Nyukawa Group exposed about 60km northeast of the present area, and indicates the Yakhtashian to Kubergandian of the standard stratigraphic scheme of the Tethyan Province.
Thirty-two mollusc species were identified from two localities of the lower Middle Miocene Ausinskaya Formation around Novoselovo, southwestern Sakhalin. This fauna includes a number of warm-water taxa such as Anadara watanabei, Glycymeris cisshuensis, Dosinia tugaruana, Tateiwaia sp., Euspira meisensis, and Cultellus izumoensis. These taxa were previously unknown in the Ausinskaya Formation, except for Cultellus izumoensis. A Dosinia-Anadara association made up of subtropical to temperate-water euneritic dwellers is prominent in this fauna, as is a temperate- to cold-water, eu- to mesoneritic Spisula association that has been recognized in lower Middle Miocene strata of northwestern Hokkaido and northwestern Sakhalin. The cooccurrence of these two ecologically dissimilar faunal associations implies that adjacent warm (inshore) and cold (offshore) water masses were present within the temperate marine realm that prevailed in Hokkaido and in southwestern Sakhalin during the early Middle Miocene.