Charrieau, L. M., Kawagata, S., McIntosh, I., Tamura, Y., Nagai, Y. and Toyofuku, T., in press: Recent deep-sea benthic foraminifera from an active volcanic area: first insights around Nishinoshima, Northwest Pacific. Paleontological Research. 10.2517/PR220024. オンライン公開日2023年02月02日. PDF
This study reports the preliminary results of the first analysis of benthic foraminifera of seafloor surface sediments from the Nishinoshima volcanic area. The samples were collected in 2015 during several DEEP TOW (deep ocean floor towed survey system) dredges on the summit and flank of Nishinoshima-Minami Knoll, a knoll ~8 km southeast of Nishinoshima Island that forms part of the same submarine volcanic edifice. The two stations DT-1170 (N9) and DT-1173 (N12) were sampled from water depths of 1062–1015 m and 516–203 m, respectively, and were located at distances of 10 and 8 km from the main Nishinoshima edifice, respectively. The two stations displayed a typical faunal structure for deep-sea environments, with low foraminiferal densities but highly diversified assemblages. A total of 131 species, excluding undetermined porcelaneous and hyaline species groups, were found, and are recent deep-sea benthic foraminifera previously identified in the bathyal depths around Izu-Bonin volcanic arc, or species found in the Neogene onland strata in the western Pacific region. We conclude that the bathyal benthic foraminiferal assemblages in the studied area are likely to be free from recent volcanic activity. We provide detailed taxonomic descriptions of the 21 commonly occurring species. This exploratory study therefore provides crucial basic information about benthic foraminiferal faunas in the Nishinoshima area, which could be used in future environmental analysis of this highly dynamic region.
Ito, T., Matsuoka, A. and Yokoyama, H., in press: Spirally-coiled radiolarians in the latest Jurassic–earliest Cretaceous. Paleontological Research. 10.2517/PR220026. オンライン公開日2023年01月20日. PDF
Polycystine radiolarians have siliceous shells. The shells of Nassellaria, one of the major orders of radiolarians, are generally tower-like. Spiral structures are known in the shells (e.g. Sashida and Tonishi, 1991) and spines (e.g. De Wever et al., 2003) of other radiolarians; however, none with spiral shells had been found in Nassellaria. We found two different genera of Nassellaria with spiral shells from the latest Jurassic–earliest Cretaceous sample from the Mariana Trench. The findings are extremely rare and are important when considering the shell formation in radiolarians. The sample is a laminated tuffaceous radiolarian claystone or clayey radiolarite collected from the Mariana Trench oceanward slope (147° 50.6’E/15° 28.7’N: 6,316 m water depth) by “Shinkai 6500” of JAMSTEC (Japan Agency for Marine-Earth Science and Technology). Because of the occurrences of the Loopus primitivus (Matsuoka and Yao) and Pseudodictyomitra carpatica (Lozyniak) (Matsuoka, 1998), the sample was considered to correspond to the lower part of the Pseudodictyomitra carpatica Zone (KR1) (uppermost Tithonian to lower Berriasian, uppermost Jurassic–lowermost Cretaceous) by Matsuoka and Ito (2019). Further detailed information on the sample and cooccurring radiolarian species are mentioned in Matsuoka (1998). The sample yielded two specimens having spiral shells. Such specimens are called “spiral-mutant” in this article. The first specimen of the spiral-mutant belongs to Svinitzium pseudopuga Dumitrica (Figure 1). The shell of the spiral-mutant specimen appears to be uncoiled up to the third septa from the top, but from the fourth septa onward, the shell tilts in opposite directions on the front side (Figure 1A1, A2) and the back side (Figure 1A3, A4), indicating a spiral coiling structure. In contrast, all the septa of the normal specimens (Figure 1B, C) are parallel and uncoiled. The second specimen belongs to Xitus Pessagno (Figure 2). Oblique septa can be observed in the lower part of the shell of the spiral-mutant specimen (Figure 2A); parallel septa are recognized in the normal specimens (Figure 2B, C). Some researchers have observed the growth processes of radiolarian skeletons (e.g. Anderson, 1981; Matsuoka, 1992; Suzuki, 2006; Ogane et al., 2010; Lazarus et al., 2021). Lazarus et al. (2021, p. 58) showed Nassellaria specimen and noted, “the degree to which cellular growth control mechanisms are increasingly limited in effectiveness as growth extends further away from the point of origin (the first cephalic segments).” The spiral-mutant specimens shown in this article seem to have an uncoiled structure in the upper part of the shell (Figures 1A, 2A), consistent with the description by Lazarus et al. (2021). Shells of a unicellular organism has strictly-formed parts according to its “body plan” and parts that are not. The former parts are essential for survival and are ecologically relevant. The accumulation of examples, such as the spiral-mutant specimens reported in this study, should lead to a better understanding of the shell formation with intracellular roles and growth processes of radiolarians. Further, this will be an important knowledge for radiolarian paleoecology and taxonomy.
Tatehata, J., Mukunoki, T. and Tanoue, K., in press: Description of a titanosauriform (Sauropoda, Dinosauria) cervical vertebra from the Lower Cretaceous Kanmon Group, southwestern Japan. Paleontological Research. 10.2517/PR220009. オンライン公開日2022年10月11日. PDF
A fragmentary and yet to date the largest single bone element from the Lower Cretaceous Kanmon Group in Kyushu Island, southwestern Japan is described. This specimen has a fossa and lenticular foramen on its lateral surface and internal chambers of both large and small sizes. It was identified as the cervical vertebra of a titanosauriform sauropod dinosaur mainly based on such pneumatic structure. This specimen represents the first titanosauriform to be described from the Kanmon Group.
Tanaka, Y., Nagasawa, K. and Oba, S., in press: A new fossil rorqual aff. Balaenoptera bertae specimen from the Shinazawa Formation (late Pliocene to early Pleistocene), Yamagata, Japan. Paleontological Research. 10.2517/PR210038. オンライン公開日2022年05月25日. PDF
More than 23 extinct species and 10 extant species of the Balaenopteridae are known. Our knowledge of the family Balaenopteridae is increasing quickly, however, few fossil records support a circum-north Pacific distribution of balaenopterid genera and species. Because of limited preservations, most rorqual fossils reported from the western North Pacific can only be identified to the family level. A skull from the Shinazawa Formation (late Pliocene to early Pleistocene) in Yamagata, Japan, is identified as aff. Balaenoptera berate by possessing two diagnostic features of the species: large occipital condyles, and a posteriorly elongate postglenoid process. Combination of four more features also support that the specimen is a closely related to B. bertae. The specimen is probably a slightly older individual than the holotype of B. bertae, based on the estimated bizygomatic width and slightly longer posterior process of the tympanoperiotic. The first and only report of B. bertae was from the Pliocene Purisima Formation in California, USA. The specimen from Japan is incompletely preserved, but implies that the occurrence of B. bertae in the western North Pacific for the first time, as many living balaenopterids are distributed across the North Pacific, such as Balaenoptera musculus, B. physalus, B. borealis, B. acutorostrata, and Megaptera novaeangliae.
Ishida, Y., Kaneko, M., Yokobori, A., Mita, R., Ishikawa, H., Thuy, B., Numberger-Thuy, L. D., Fujita, T., in press: Amphiura multispina (Ophiuroidea, Amphiuridae) from the upper Pleistocene Kioroshi Formation in a drill core at Nagareyama, Chiba, central Japan. Paleontological Research. 10.2517/PR220001. オンライン公開日2022年04月27日. PDF
Over 100 well-preserved dissociated ophiuroid arm ossicles, i.e., lateral arm plates, dorsal arm plates, ventral arm plates, vertebrae and arm spines, were recovered from the upper Pleistocene Kioroshi Formation in the core of borehole GS-NY-1 at Nagareyama, Chiba Prefecture, central Japan. Following comparison with the lateral arm plates of ten extant amphiurid species occurring in the seas around Japan and with previously published fossil taxa in this family, the ossicles from Nagareyama were identified as belonging to the extant species, Amphiura multispina. This is the first fossil record of this form and the stratigraphically youngest of the Amphiuridae. The taphonomy and paleoenvironment of the brittle star fossils described are also discussed.
Sasaki, S., Irizuki, T., Itaki, T., Tokuda, Y., Ishiwa, T. and Suganuma, Y., in press: Relationship between modern deep-sea ostracods and water mass structure in East Antarctica. Paleontological Research. 10.2517/PR210033. オンライン公開日2022年01月25日. PDF
This study investigated the relationship between the distribution of modern ostracod biofacies and environmental factors in Lutzow–Holm Bay, off Cape Darnley, and off Totten Glacier in East Antarctica. We collected study samples from water depths of 219 to 987 m by the 61st Japanese Antarctic Research Expedition. Nineteen species belonging to 13 genera and 47 species belonging to 31 genera of ostracods were found in three samples from Lutzow–Holm Bay and ten samples from off Totten Glacier, respectively. We found no ostracods in the samples off Cape Darnley. Q-mode cluster analysis reveals four ostracod biofacies (A to D). Antarctiloxoconcha frigida (Neale, 1967) and Australicythere polylyca (Muller, 1908) were common under the influence of cold water in the upper bathyal zone (biofacies A to C). The genus Krithe was the most abundant taxon in biofacies D with low dissolved oxygen and high-water temperature (0.38℃, 34.66, and 5.0 ml/L, respectively), indicating the presence of warm deep seawater, i.e., modified Circumpolar Deep Water. Thus, we have checked the relationships between the ostracod assemblages and the environmental parameters analyzed in Lutzow–Holm Bay and off Totten Glacier, and so strengthened the previous ostracod and environmental data.
Takahashi, Y. and Aiba, H., in press: A fossil paper wasp (Vespidae: Polistinae) from 1 the Chibanian (Middle Pleistocene) Shiobara Group in Tochigi Prefecture, Japan. Paleontological Research. 10.2517/PR210027. オンライン公開日2022年01月25日. PDF
A specimen belonging to the genus Polistes (Vespidae: Polistinae) is described from the Chibanian (Middle Pleistocene) Shiobara Group, Tochigi Prefecture, Japan. The morphology of the forewing and first gastral tergum indicated a more accurate assignment of Polistes sp. This specimen the first fossil of a paper wasp to be identified in Japan.
Nishioka, Y. and Tomida, Y., in press: Taxonomic revision of lower Miocene pecorans (Mammalia, Artiodactyla) from Japan, with a new fossil record of stem Cervidae. Paleontological Research. 10.2517/PR210019. オンライン公開日2021年12月21日. PDF
The origin and early dispersion of crown groups (e.g. Cervidae and Bovidae) in pecorans are traced back to the late Oligocene or early Miocene in Eurasia. The fossil pecorans from the lower Miocene of Japan are highly fragmentary but form evidence of a zoogeographic connection between Japan and the Eurasian continent during this period. In this study, we described dental fossils (seven specimens) from five Burdigalian formations (Nakamura Fm. ~18.5 Ma; Hiramaki Fm. ~18 Ma; Misawa Fm. and Kitatage/Asakawa Fm. ~17 Ma; Kunimi Fm. ~16 Ma), and as a result of taxonomic revision we recognized four species, including a basal species of Cervidae, Dicrocerus? tokunagai, cf. Palaeomeryx minoensis, and Amphimoschus sp. These species have the basic occlusal patterns of cheek teeth inherited from primitive pecorans (e.g. Amphitragulus), but each species displays advanced characteristics, such as full selenodonty, a weak/no external postprotocristid, and a bicuspidate third lobe of m3 ( Amphimoschus). The early group of crown pecorans composed of basal cervids (Lagomerycinae or Procervulinae), Palaeomeryx s.l., and Amphimoschus, had dispersed widely in Europe (early Orleanian or MN3) and East Asia (Shanwangian), including Japan. Our findings on the Japanese fossil records demonstrate that the dispersion of a basal cervid and palaeomerycid between Japan and the Eurasian continent had been completed before 18 Ma. Further studies with additional material would reveal detailed taxonomic relationships and evolutionary process of the Japanese pecorans in the Burdigalian.
Changae, K., Babazadeh, S. A., Arian, M. and Pirbaloti, B. A., in press: Systematic paleontology of Bartonian larger benthic foraminifera from Shahrekord region in High Zagros, Iran. Paleontological Research. 10.2517/PR200055. オンライン公開日2021年12月06日. PDF
The Jahrum Formation is characterized by abundant benthic foraminifera in carbonate beds, partly marly and dolomitic limestones at the Kuh-e-Soukhteh (Shahrekord region). This formation covers a huge stretch of the Zagros Zone which is a part of the central Tethyian realm during the Paleogene time. Biostratigraphic analysis of the larger benthic foraminifera is deduced to distinguish one assemblage zone assigned to the late Middle Eocene (Bartonian). This new biostratigraphic range is represented by the index fossil of Rhabdorites malatyaensis (Sirel) and correlated with calcareous rocks in the Shiraz area (south Iran), Dhofar section (Oman), and Socotra Island (Yemen). The Jahrum Formation is dominated by rich miliolids-agglutinated foraminifera with rare small rotaliids and without Nummulites Lamarck and Alveolina d'Orbigny indicating that the formation was deposited in a shallow water environment (nearshore lagoonalzone) with low energy.
Tanabe, Kazushige, in press: Late Cretaceous dimorphic scaphitid ammonoid genus Yezoites from the circum-North Pacific regions. Paleontological Research. 10.2517/ PR200049. オンライン公開日2021年08月25日. PDF
Yezoites is a Late Cretaceous (Cenomanian–Campanian) small to very small dimorphic ammonoid genus belonging to the Scaphitidae, whose microconchs have a pair of long lateral lappets at the aperture. Based on examination of previously described material including type- and figured specimens and newly recovered ones, five species of Yezoites are described herein from the circum-North Pacific regions (Japan, Sakhalin, Kamchatka, Alaska, Oregon, and California); i.e., Y. perrini (Anderson), Y. seabeensis Cobban and Gryc, and Y. puerculus (Jimbo) from the Turonian, and Y. pseudoaequalis (Yabe) and Y. matsumotoi (Tanabe) from the Coniacian. Of these species, both microconchs and macroconchs are recognized in Y. puerculus and Y. pseudoaequalis, whereas only microconchs are known in the other three species.
These Yezoites species characteristically occur in very fine-grained sandstone to sility mudstone facies suggesting an intermediate between nearshore and offshore environments, and can be used for biozonation and correlation of the Turonian and Coniacian deposits in the North Pacific regions.
Shigeta, Y., in press: Revision of early Spathian (late Olenekian, Early Triassic) ammonoids from the Osawa Formation at Akaushi in the Motoyoshi area, South Kitakami Belt, Northeast Japan. Paleontological Research. 10.2517/2021PR009. オンライン公開日2021年06月03日. PDF
A taxonomic revision of the ammonoid assemblage previously reported from the Osawa Formation at Akaushi in the Motoyoshi area, i.e., Columbites parisianus, Subcolumbites perrinismithi and Eophyllites cf. dieneri, leads to the conclusion that the fauna should be attributed to Hellenites tchernyschewiensis, H. inopinatus, Neocolumbites grammi, N. insignis, Procolumbites ussuriensis and P. subquadratus. In addition, this fauna also includes Deweveria kovalenkoi. Because these ammonoids are characteristic of the N. insignis Zone of South Primorye, Russian Far East, the lowest part of the Osawa Formation clearly correlates with the upper part of the lower Spathian (upper Olenekian, Lower Triassic), and the faunal similarity suggests that the South Kitakami Belt may have been located near South Primorye on the western side of the Panthalassa.
Shigeta, Y. and Izukura, M., in press: Discovery of the heteromorph ammonoid Amapondella amapondense in the middle Campanian of Hokkaido, Japan. Paleontological Research. 10.2517/2021PR008. オンライン公開日2021年05月22日. PDF
The discovery of the heteromorph ammonoid Amapondella amapondense (van Hoepen) in the lower middle Campanian in the Urakawa, Biratori and Hidaka areas of Hokkaido, northern Japan, represents the first report of this taxon in the Northwest Pacific region. Because the species flourished in other regions during Santonian to early Campanian time, its final geographic occurrence in Hokkaido suggests that global environmental changes likely had a significant influence on ammonoid biogeography during early middle Campanian time.