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Miocene-Pliocene foraminifera recovered from three subsurface sections in the Yufutsu Oil and Gas Field, southern Hokkaido, are studied in detail to infer paleoceanographic and paleobathymetric implications and to clarify the history of the basin. Foraminiferal faunas indicate a progressive increase in bathymetry from a brackish shallow marine to a bathyal condition during the Middle Miocene. The basin then came under the spell of volcanism and nearly 1000 m of basalt-basaltic andesite flows accumulated until the top of the volcano emerged out of the sea. After the cessation of volcanic activity, the basin subsided and cold bathyal conditions prevailed in which diatomaceous-siliceous sediment was accumulated during the Late Miocene. The periodic episodes of subsidence are inferred to have been related to the genesis of the Japan Sea. The basin witnessed a major hiatus during the Late Miocene-Early Pliocene. During the Late Pliocene, coarse clastic sediments accumulated in the region in a cold bathyal condition of deposition. The clastic sediment is thought to have derived from the eastern upland where the Upper Cretaceous and Paleogene sedimentary rocks were exposed. It is supposed that the hiatus in the Late Miocene-Early Pliocene is a result of an upheaval of central Hokkaido, which unstabilized the sediment and changed bottom current condition.
The Early to Middle Miocene microfauna of the region is similar to those of the Japan Sea region, whereas the Late Miocene fauna is different in abundance of agglutinated foraminifera. Such faunal differences between the study area and Japan Sea region of Honshu in the Late Miocene are mainly due to the variable distances from the proto-Tsugaru Strait that let carbonate-saturated Pacific seawater into the Japan Sea.
Clupea tanegashimaensis was described by Saheki (1929) on the basis of a single specimen from Sumiyoshi, Katanoyama, Tanegashima Island, Japan. The holotype is reexamined and redescribed with additional specimens excavated from the type locality in 1988 and 1989. This species is not a member of the genus Clupea. It belongs to the genus Clupanodon because of the presence of dorsal scutes and the elongated last dorsal fin ray. The fossil fish fauna from Tanegashima has the potential to be an important basis for understanding the origin and evolution of a number of species in the Pacific coastal fish fauna.
The ostracode fauna from the middle–upper Eocene Iwaya Formation on Awajishima Island, Hyogo Prefecture, southwestern Japan was studied to reveal a band of the Eocene ostracode faunal spectrum in the middle latitudes of the northwestern Pacific. Based on lithofacies and previously reported calcareous nannofossils, molluscs, and benthic foraminifers, the ostracodes were found to have inhabited inner shelf environments. The ostracodes entirely differ from the Eocene–earliest Oligocene faunas in Kyushu, southwestern Japan and the East China Sea, both in generic and specific composition. The difference is considered to be due to paleoclimatic and paleogeographic differences between Awajishima Island and more southern latitudes at that time.
Described species include three new species, Munseyella setouchiensis sp. nov., Hanaiborchella reticularitriangularis sp. nov., and Trachyleberis awajiensis sp. nov.
Sanitheres are poorly understood suiforms of small body size. Recent advances in knowledge have been made, especially regarding their postcranial skeleton, but, apart from dentognathic remains, the cranium remains incompletely known. Field work in the Middle Miocene Aka Aiteputh Formation, near Baragoi, Kenya, has resulted in the recovery of a snout and a crushed neurocranium of Diamantohyus nadirus which throw a great deal of light on the systematic affinities of the sanitheres, but do not completely resolve their phylogenetic status.
Mesozoic gastropod assemblages currently emerged from Kutch, western India constitute one of the most diverse communities known during the Bathonian–Oxfordian worldwide. The present paper describes part of the Jurassic gastropod faunas of the family Pleurotomariidae from Kutch, comprising ten species belonging to three genera, of which eight species are new. They are: Bathrotomaria reticulata (Sowerby), B. waageni sp. nov., B. calloviana sp. nov., B. buddhai sp. nov., B. prasantai sp. nov., B. dhosaensis sp. nov., B. tewarii (Maithani); Leptomaria daityai sp. nov.; L. asurai sp. nov. and Obornella wuerttembergensis (Sieberer). The assemblage shows a strong Tethyan affinity at generic level, but has a distinctly endemic species content, and thus merits a distinct subprovince within the Indo-Madagascan Faunal Province. The genus Pleurotomaria is discussed in historical perspective and shown to be Mesozoic genus. The six species of Bathrotomaria described herein are considered to have evolved from the early immigrant species, B. reticulata of Europe.