The early Pleistocene ostracod fauna from the Hamada Formation (ca. 1.5–1.2 Ma) was investigated in the Shimokita Peninsula, northeastern Japan. Twelve samples of this fossil fauna yielded 184 species, many of which are representative upper-shelf ostracods in the modern northeastern Japan Sea. Three biofacies were defined by Q-mode cluster analysis. The two most abundant species for each biofacies are Neonesidea sp. and Schizocythere kishinouyei in biofacies N, Buntonia hanaii and Yezocythere hayashii in biofacies B, and Laperousecythere robusta and Finmarchinella daishakaensis in biofacies L. The depositional environment of the individual biofacies can be defined as (1) upper-shelf area under open-sea influence in relatively high salinity (biofacies N), (2) inner—central-bay area, with relatively low salinity (biofacies B), and (3) bay-mouth area with intermediate salinity levels between those of (1) and (2) (biofacies L). Water depth decreased from the upper-shelf area through to the bay-mouth and then to the inner-central-bay areas during the depositional period of the studied horizons. The palaeoceanographic setting during most of the depositional period was estimated as the conditions of a water mass similar to the present Japan Sea Central Water, while surface waters were influenced by currents similar to the modern Tsugaru Warm and Oyashio Cold Currents. Based on the species content of biofacies B, Buntonia and Yezocythere commonly inhabited shallow inner-bay areas around 1.2 Ma in this region, instead of the modern representative inner-bay taxa of Japan which first appeared in the northernmost Honshu region after 1.0 Ma. The occurrence mode for extant and now-extinct species of the families Hemicytheridae, Cytheruridae and Eucytheridae suggests that the ostracod fauna in the upper-shelf environment from the Hamada Formation was similar to those from the southwestern to northeastern Japan Sea coast during the same period, even though it is situated at the easternmost extremity of the Japan Sea coastline (ca. 141°E) near the Pacific.

A total of 92 species or taxa of polycystine radiolarians were identified in depth-stratified plankton samples collected from the Tsushima Strait between Japan and Korea in autumn 2006. This assemblage can be divided into three groups: shallow eastern channel, shallow western channel, and bottom western channel. The distribution patterns are most likely related to different water masses. The western channel is influenced mainly by the Taiwan Current and coastal waters, which are characterized by low salinity and high nutrients, whereas water in the eastern channel is mainly from the Kuroshio Current. Cycladophora davisiana, which lives deeper than 500 m in the Japan Sea, was abundant in the western channel at 100–140 m. This suggests that the deeper microzooplankton in the Tsushima Strait are associated with colder and less saline water originating from the greater depths of the Japan Sea.

Intra- and interspecific variation and ontogenetic changes in various shell characters of the Late Cretaceous desmoceratine ammonoid “Damesites” are described, and their taxonomic implications are discussed based on specimens from the Cretaceous Yezo Group in Hokkaido and Sakhalin. Our study reveals that many “diagnostic” features (e. g., appearance of longitudinal striations, height of ribbing, regularity of ribbing as well as constriction curvature) and early internal shell structures, are in fact inappropriate as diagnostic features of “Damesites” morphotypes. In contrast, ontogenetic changes in shell ornament, curvature of growth lines and whorl expansion ratio are herein demonstrated to be key characters for species recognition and reconstructing the phylogenetic relationships of the taxa of the subfamily Desmoceratinae. Based on these results, previously described “Damesites” species from the uppermost Turonian-lower Campanian interval should be reclassified into three groups. “Damesites damesi,” “D. damesi intermedius,” “D. semicostatus,” and “D. laticarinatus” are assigned to the first group. “D. ainuanus” and “Damesites sp.” are assigned to the second group. “D. sugata” from the Yezo Group represents the third group. Furthermore, analysis of ontogenetic changes in shell ornament, curvature of growth lines, and whorl expansion ratio suggests that the second and third groups together belong to a different evolutionary lineage from the first group.

Based on materials from the Krasnoyarka Formation in the Naiba area in south Sakhalin, Russia, taphonomic histories of a large Campanian ammonoid, Canadoceras kossmati Matsumoto, 1954, were closely investigated. Large Canadoceras shells exceeding 30 cm in diameter are usually embedded horizontally and solitarily in muddy sandstone. A thin, lenticular calcareous concretion envelopes the shell (= envelope concretion). Their body chambers are mostly lost. The inner whorls comprising the center of the umbilicus completely disappear without exception, and only two or three outer whorls are preserved. The body and air chambers are somewhat compressed by compaction and are filled with sediments. Phycosiphon burrows are common not only in open body chambers but also in inner air chambers, which were originally closed. These observations suggest that the thin-shelled inner whorls and organic-rich siphuncular tubes degraded before final burial of the shell, and sediment infilling to the inside of the chambers followed. The early loss of inner whorls and siphuncular tubes gave rise to “draft-through currents.” The continuous supply of oxygen and nutrients by the draft-through currents supported the Phycosiphon producers in the inner air chambers. Compared with other calcareous concretions containing intact fossils, values of minus-cement porosity (MCP) remain relatively low (63–74%) and vary by areas even in the same envelope concretion. This indicates that the envelope concretions were cemented under a progressive increase of compaction during the later diagenetic stage. The formation of the envelope concretion appears to be a long-term phenomenon. Various events at different stages have been overprinted in a single large ammonoid fossil.

Remains of 11 species of extinct elasmobranch were obtained from the Oligocene Yamaga Formation on Ainoshima Island in northern Kitakyushu City, Japan. More than 360 gill rakers belonging to a basking shark (Cetorhinus sp.) individual were collected from a stratigraphic horizon in the northern part of the island. This report represents the highest concentration of basking shark gill rakers in the fossil record of Japan.

Based on sedimentary facies analysis combined with habitat data of extant sharks, habitats of Oligocene elasmobranchs were reconstructed. The result indicates that Oligocene sharks probably lived in an environment similar to that of extant sharks at the genus level. This does not support the previous hypotheses that some shark taxa (e.g., Hexanchus) existed within shallow environments during the Oligocene, and have since migrated into deeper water habitats. Analysis of other genera supports this hypothesis of stability in elasmobranch habitat preference, at least at the genus level, between the Oligocene and present day.