Inose, H., Furuuchi, K., Ito, T., Sashida, K. and Agematsu, S/, in press: Radiolarian fossils from conglomerate layers of the Upper Cretaceous Nakaminato Group exposed along the Pacific coast of Ibaraki Prefecture, central Japan: Staged denudation of the mid-Mesozoic accretionary complexes in the Kanto District. Paleontological Research. doi:10.2517/2017PR026. オンライン公開日2017年12月05日. PDF
The Upper Cretaceous Nakaminato Group, which contains the Chikko, Hiraiso, and Isoai formations in ascending order, crops out along the Pacific coast of Ibaraki Prefecture, central Japan. This group is composed mainly of sandstone, siltstone, and sandstone-siltstone alternations, with intercalated conglomerate layers at several levels. The siltstone of the Hiraiso and Isoai formations has yielded ammonites and inoceramid bivalves indicating a middle Campanian to Maastrichtian age. Some conglomerate layers in the Isoai Formation reach 1 m in thickness and mostly consist of pebbles and cobbles of rhyolite, dacite, chert, siliceous siltstone, siltstone, sandstone, and hornfels. We obtained late Paleozoic to Late Jurassic radiolarians from pebbles of argillaceous rock and chert from four levels of the conglomerate layers within the Isoai Formation. We describe the radiolarians systematically herein. The probable provenance of the radiolarian-bearing pebbles is interpreted as the Ashio and Yamizo terranes, which consist of Late Jurassic to Early Cretaceous accretionary complexes. We propose that there were two denudation stages of the accretionary complexes in the Kanto District, stages α (Barremian–) and β (Campanian–).
Sato, T, Hanai, T., Hayashi, S. and Nishimura, T., in press: A Turonian polycotylid plesiosaur (Reptilia; Sauropterygia) from Obira Town, Hokkaido, and its biostratigraphic and paleoecological significance. Paleontological Research. doi:10.2517/2017PR024. オンライン公開日2017年12月05日. PDF
The Polycotylidae are short-necked plesiosaurs known from theCretaceous in various parts of the world, but only a few occurrences have beendocumented in Japan where elasmosaurid remains are much more common. Anindeterminate polycotylid specimen from the Upper Cretaceous in Obira Town,Hokkaido, is described. Characteristics of the vertebrae and clavicular archsupport its taxonomic affinity. The Turonian occurrence of the specimen indicatesthe continuous presence of the Polycotylidae across the Cenomanian-Turonianboundary in the northwestern Pacific. Macroscopic osteological features of thevertebrae and clavicular arch indicate an advanced stage of ossification, and thereare histological characteristics suggesting slowed growth. The osteoporotic-likecondition implies a high degree of aquatic adaptation.
Tanaka, Y., Furusawa, H. and Barnes, L. G., in press: Fossil herpetocetine baleen whales (Cetacea, Mysticeti, Cetotheriidae) from the lower Pliocene Horokaoshirarika Formation at Numata, Hokkaido, northern Japan. Paleontological Research. doi:10.2517/2017PR025. オンライン公開日2017年12月01日. PDF
Two mandibles of fossil mysticetes from the early Pliocene, upper part of the Horokaoshirarika Formation at Numata Town, Hokkaido, Japan, belong to the archaic, extinct cetotheriid baleen whale, Herpetocetinae, gen. et sp. indet. by having an elongated angular process projecting posteriorly beyond the mandibular condyle. The new materials of the Herpetocetinae represent the northernmost occurrence in the North Pacific.
Maekawa, T., Komatsu, T., Tanaka, G., Williams, M., Stocker, C. P., Okura, M. and Umayahara, A., in press: Missourian (Kasimovian, Late Pennsylvanian) conodonts from limestone boulders, Mizuboradani Valley, Gifu Prefecture, central Japan. Paleontological Research. doi:10.2517/2017PR023. オンライン公開日2017年11月21日. PDF
Two Late Pennsylvanian conodont species, Gondolella sublanceolata Gunnell and Idiognathodus sulciferus Gunnell, were extracted from limestone boulders in the Mizuboradani Valley, Fukuji district, central Japan. These provide the first evidence of Missourian (Kasimovian) cosmopolitan conodonts in the Akiyoshi and Hida Gaien belts, Inner Zone of Japan. The limestone boulders might be derived from the Ichinotani Formation and/or from limestone clasts in conglomerates of the Permian Sorayama Formation that crop out in the Mizuboradani Valley.
Yamashita, D., Kato, H., Onoue, T. and Suzuki, N., in press: Integrated Upper Triassic conodont and radiolarian biostratigraphies of the Panthalassa Ocean. Paleontological Research. doi:10.2517/2017PR020. オンライン公開日2017年10月31日. PDF
The Late Triassic conodont biostratigraphy of two pelagic chert sections (sections N and Q) in the Inuyama area, central Japan, was investigated to calibrate the Triassic radiolarian zonation proposed by Sugiyama in 1997 with the conodont zones and the standard Triassic timescale. Based on the stratigraphic distributions of marker species, six conodont zones were defined: the Paragondolella? tadpole interval Zone, the Quadralella tuvalica interval Zone, the Epigondolella quadrata interval Zone, the E. triangularis interval Zone, the Mockina postera interval Zone, and the M. bidentata Zone. These conodont zones are comparable to the standard Carnian and Norian conodont zones of North America and the Tethys. The Carnian-Norian boundary in the sections studied is tentatively placed between the last occurrence of a Carnian species (Q. tuvalica) and the first occurrences of Norian species (E. quadrata and E. spatulata). The intercalibrated conodont–radiolarian biostratigraphy from the sections we studied accurately calibrates the radiolarian zones in Japan with standard chronostratigraphic stages and substages.
Suzuki, H., in press: Fossil evidence of the Hammerjaw fish, Omosudis sp. (Teleostei, Aulopiformes) from the Middle Miocene Yokoo Formation in Nagano Prefecture, central Japan. Paleontological Research. doi:10.2517/2017PR019. オンライン公開日2017年10月26日. PDF
A fossil palatine of an alepisauroid fish collected from the Middle Miocene Yokoo Formation in Nagano Prefecture, central Japan is described as Omosudis sp. Although the palatine is preserved as a fragment, the palatine teeth arranged in a single row are well-preserved. In fact, the palatine tooth characteristics are adequate as diagnostic at generic level identification. The fossil appears to be assignable to the genus Omosudis belonging to the family Alepisauridae by having the following characteristics: enormously large, posteriorly inclined teeth with each sharply pointed apex, apico-basal striations, a nearly straight to arcuate anterior cutting edge, a wide pulp-cavity surrounded by a thin dentine layer and a fang-like outline due to a basally elongated postapical barb. The Yokoo specimen represents the first reliable fossil record of the genus from the Middle Miocene in Japan and appears to mark the earliest occurrence of this recent genus in the Northwest Pacific region.
Sato, T., Konishi, T., Nishimura, T. and Yoshimura, T., in press: A basal mosasauroid from the Campanian (Upper Cretaceous) of Hokkaido, northern Japan. Paleontological Research. doi:10.2517/2017PR018. オンライン公開日2017年09月13日. PDF
A basal mosasauroid specimen, including a rib and a vertebra from middle to posterior portion of the trunk, is reported from the lower Campanian Inoceramus (Platyceramus) japonicus zone in Obira Town, northern Hokkaido, northern Japan. It is the second occurrence of basal mosasauroids sensu lato in Japan after the halisaurine Phosphorosaurus ponpetelegans, but represents a larger individual than the P. ponpetelegans holotype. The Obira specimen predates the early Maastrichtian P. ponpetelegans by about 10 million years, indicating colonization by basal mosasauroids of the northwestern Pacific by at latest the early Campanian age. While the overall morphology of the Obira specimen agrees well with that of a halisaurine vertebra, the presence of well-developed zygantra (zygosphenes missing postmortem if present) on the vertebra and its inclined condyle uniquely align the specimen with Pannoniasaurus inexpectatus, a Santonian-aged basal mosasauroid from freshwater deposits in Hungary.
Yamada, in press: Plant fossils from the Arimine Formation (Oxfordian, Jurassic) of the Tetori Group in Arimine, Toyama Prefecture, Central Japan. Paleontological Research. doi:10.2517/2017PR017. オンライン公開日2017年08月27日. PDF
Ptilophyllum sp. and Zamites brevipennis are newly described from the middle Oxfordian Arimine Formation in Arimine area, Toyama Prefecture, Central Japan. These two species characterize the vegetation of the Eurosinian paleophytogeographic province where a climate with dry season(s) prevailed. This finding, as well as the presence of a Kaizara Flora, suggests that Eurosinian-type vegetations continuously flourished during the late Bathonian to Oxfordian on the land of the Tetori Group. We also infer that Tetori-type floras first appeared during the Tithonian in the Tetori Group.
Jenkins, R. G., Kaim, A., Amano, K., Sakurai, K. and Matsubara, K., in press: A new Miocene whale-fall community dominated by bathymodiolin mussel Adipicola from Hobetsu area, Hokkaido, Japan. Paleontological Research. doi:10.2517/2017PR006. オンライン公開日2017年06月23日. PDF
We report the fourth record of a fossil whale-fall community in Japan. The new material consists of a single whale bone associated mainly by small bathymodiolin mussels, Adipicola sp., found in the Karumai Formation (late middle Miocene–early late Miocene) in the Hobetsu area of Hokkaido, Japan. This association of whale bone and Adipicola sp. and its mode of occurrence resembles the description of some other ancient whale-fall communities dominated by small mussels from the Olympic Peninsula in Washington State (early Oligocene), Shosanbetsu in Hokkaido (early middle Miocene) and Carpineti in northern Italy (middle Miocene) and constitutes an example of a chemosynthesis-based community sustained by whale–fall decay in the Miocene deep sea. The new example extends the Miocene distribution of bathymodiolin dominated whale-fall communities to the northwestern Pacific Ocean.
Wang, Y. and Wang, Y., in press: Globusphyton Wang et al., an Ediacaran macroalga, crept on seafloor in the Yangtze Block, South China. Paleontological Research. doi:10.2517/2017PR005.. オンライン公開日2017年06月21日. PDF
The Ediacaran genus Globusphyton Wang et al., only including one species G. lineare Wang et al., is a eukaryotic macroalga in the Wenghui biota from black shale of the upper Doushantuo Formation (ca. 560–551 Ma) in northeastern Guizhou, South China. It was assigned as one of significant fossils in the assemblage and biozone divisions in the middle-late Ediacaran Period. Morphologically, Globusphyton is composed of several structural components, displaying that it had tissue differentiation to serve various bio-functions. Its prostrate stolon, a long ribbon bundled by unbranching filaments, crept by holdfasts on the seafloor. Its pompon-like thalli, the circular to oval thallus-tuft composed of many filamentous dichotomies, may have served for photosynthesis. The fusiform ribbon-tubers, the caked and expanded segments of the ribbon, may have served to sustain the growth of the thalli and the possible holdfasts. The zigzag-shaped stolon and pompon-like thalli of Globusphyton, in a relatively low-energy environment,were crept on the surface of the muddy sediments and suspended in water column, respectively. When water current occurred occasionally, all or part of its body was probably suspended in the water column to be deformed as a variable pattern.