Volumes & issues:
A New and Ontogenetically Younger Specimen of Numataphocoena yamashitai from the Upper Part of the Horokaoshirarika Formation (Lower Pliocene), Numata, Hokkaido, Japan20, 2(2016); http://dx.doi.org/10.2517/2015PR026View Description Hide DescriptionAbstract.
A new periotic of Numataphocoena yamashitai from the upper part of the Horokaoshirarika Formation (lower Pliocene), Numata, Hokkaido, Japan shows younger ontogenetic features in comparison to the matured holotype (NFL 7). The referred specimen of N. yamashitai is smaller (approximately 90% in size) than the physically and sexually matured holotype periotic. The holotype (NFL 7) and referred specimen (NFL 2617) show several differences owing to ontogenetic changes, such as: the holotype (NFL 7) has a more strongly swollen medial part of the anterior process, blunt anterior keel, rounded anterodorsal angle, deeper and clearer anterior incisure, more rounded pars cochlearis, deeper and narrower hiatus epitympanicus rather than a flat area, longer posterior process with an extra edge posterolaterally. N. yamashitai differs from other fossil phocoenids in having a narrower and sharper anterior part of the internal acoustic meatus and a robust anterior process. Haborophocoena toyoshimai similarly has a relatively narrow internal acoustic meatus and a robust anterior process, compared with other fossil phocoenids. Between N. yamashitai and H. toyoshimai, N. yamashitai has a narrower internal acoustic meatus and a more robust anterior process. These similarities imply a close relationship between Numataphocoena and Haborophocoena. The new specimen provides diagnostic features and insight into ontogenetic variation of N. yamashitai.
20, 2(2016); http://dx.doi.org/10.2517/2015PR027View Description Hide DescriptionAbstract.
This paper describes the first record of the heteromorph ammonoid Diplomoceras cylindraceum from the uppermost Maastrichtian Kawaruppu Formation of the Nemuro Group, southeastern Hokkaido, Japan. D. cylindraceum was found in a siltstone 15 m below the Cretaceous/Paleogene (K/Pg) boundary. The stratigraphical level of the fossil is estimated to be ∼66.8 Ma, based on the time scale for the geomagnetical polarity and the K/Pg boundary. D. cylindraceum, therefore, was living at least ∼0.8 m.y. before the K/Pg boundary event in the north Pacific region.
Early to Middle Miocene Ostracods from the Yatsuo Group, Central Japan: Significance for the Bathyal Fauna between Japan Sea and Northwest Pacific Ocean During the Back-Arc Spreading20, 2(2016); http://dx.doi.org/10.2517/2015PR028View Description Hide DescriptionAbstract.
This study investigated early to middle Miocene ostracods from the Yatsuo Group (ca. 17–15 Ma), located on the Japan Sea coast of central Japan. Ostracods from this area consist of 100 species in 60 genera, with two assemblages defined by Q-mode cluster analysis. The five most abundant genera of each assemblage are Krithe, Propontocypris?, Cytherella, Argilloecia, and Falsobuntonia in assemblage A, and Schizocythere, Cornucoquimba, Callistocythere, Neomonoceratina, and Paracytheridea in assemblage B. The depositional environment of each assemblage can be defined as (1) outer-shelf to bathyal areas (assemblage A) and (2) inner-shelf areas (assemblage B). Stratigraphic changes in the faunal composition, with changes in lithofacies, suggest a shallowing-upward phase in this sedimentary basin. These assemblages contain the same species or genera as corresponding Pacific faunas in the early to middle Miocene. The assemblage containing bathyal genera such as Cytherella and Krithe from Yatsuo at 17–16 Ma is the oldest record from the entire Japan Sea coast, and their fossil records are common to Cenozoic bathyal genera among the Pacific fauna. This fact indicates that these genera could migrate from the Pacific Ocean through the deep-sea passageway to the Japan Sea since at least around 17 Ma during the early Miocene. The shallow-water assemblage of the inner-shelf area around 15.7 Ma has only a small percentage of cold-water genera. The paleo-water temperature in the shallow-sea area around 15.7 Ma in Yatsuo would have been intermediate between warm (subtropical) and cold marine climates around 16 Ma in the Japanese Islands. The ostracod fauna from Yatsuo is significant for the paleogeography and faunal migration of benthos in the Northwest Pacific Ocean during the formation period of the Japan Sea caused by back-arc spreading.
New Fossil Record of the Genus Bathynomus (Crustacea: Isopoda: Cirolanidae) from the Middle and Upper Miocene of Central Japan, with Description of a New Supergiant Species20, 2(2016); http://dx.doi.org/10.2517/2015PR029View Description Hide DescriptionAbstract.
Three species of the cirolanid isopod genus Bathynomus are reported from the Miocene deposits of central Japan. Bathynomus kominatoensis sp. nov. and an unidentified Bathynomus sp. 1 are described from the upper Miocene Amatsu Formation in the Kominato-Osawa area, Chiba Prefecture. Another large species, Bathynomus sp. 2, was obtained from the middle Miocene Negishi Formation in the Iwadono Hills area, Saitama Prefecture. The new species most resembles Bathynomus giganteus, inhabiting the deep-sea floor of the Western Atlantic and Caribbean Sea. In addition to the large-sized body, Bathynomus kominatoensis sp. nov. and Bathynomus sp. 2 are included in the supergiant species group of the genus based upon morphology of the pleotelson and uropods. Both occurrences extend the geographic and stratigraphic ranges for the supergiant species group of Bathynomus into the Miocene of central Japan, although no species of the supergiant group is distributed in modern Japanese waters.
Late Carboniferous Coiled Nautiloids from the Lost Branch Formation of Oklahoma, Midcontinent North America20, 2(2016); http://dx.doi.org/10.2517/2015PR020View Description Hide DescriptionAbstract.
Five species of coiled nautiloids are described from a black concretionary shale (uppermost Desmoinesian; middle upper Carboniferous) of the Lost Branch Formation in northeast Oklahoma, Midcontinent North America. They include a tainoceratid, Metacoceras sp., a grypoceratid, Domatoceras collinsvillense sp. nov., a solenochilid, Solenochilus sp., and the liroceratids, Hemiliroceras reticulatum (Miller and Owen) and Peripetoceras sp. Domatoceras collinsvillense is closely similar to D. umbilicatum Hyatt, but it differs in the possession of a narrower umbilical area and more compressed whorls. New material of H. reticulatum indicates an evolute conch with a shallowly concave impressed zone, characters that warrant the present new combination. The species was previously placed in Coloceras or Liroceras. This discovery of H. reticulatum from the Desmoinesian shale extends downward the stratigraphic range of this genus from the lower Permian to the upper Carboniferous.
Three New Brachiopod Species from the Middle Permian (Wordian) of the South Kitakami Belt, Northeastern Japan20, 2(2016); http://dx.doi.org/10.2517/2015PR021View Description Hide DescriptionAbstract.
This paper describes the following three new species of brachiopods from the middle Permian (Wordian) of the Kamiyasse—Imo area, South Kitakami Belt, northeastern Japan: Isogramma nakamurai, Globiella kamiyassensis and Rhipidomella magna. The newly described species are regarded as additional components of the Wordian mixed Boreal—Tethyan brachiopod fauna of the South Kitakami Belt.
Ammonoid Fauna of the Upper Olenekian Osawa Formation in the Utatsu Area, South Kitakami Belt, Northeast Japan20, 2(2016); http://dx.doi.org/10.2517/2015PR024View Description Hide DescriptionAbstract.
A late Olenekian (Early Triassic) ammonoid fauna is described from the Osawa Formation in the Utatsu area, South Kitakami Belt, Northeast Japan. The fauna comprises 14 species belonging to 13 genera: Hemilecanites discus (Arthaber), Albanites sheldoni (Kummel), Pseudosageceras? sp., Pseudokymatites tabulatus sp. nov., Columbites parisianus Hyatt and Smith, Tardicolumbites aff. tardicolumbus Guex et al., Yvesgalleticeras sp., Subcolumbites sp., Hellenites elegans Guex et al., Metadagnoceras sp., Procarnites sp., Leiophyllites wakoi sp. nov., Leiophyllites? sp., and Nordophiceratoides bartolinae Guex et al. Among them, genera Hemilecanites, Albanites, Pseudokymatites, Tardicolumbites, Yvesgalleticeras, Hellenites, and Nordophiceratoides are described for the first time from the Japanese Triassic. The generic composition of the ammonoid fauna of the Osawa Formation has thus increased to 25 genera by adding these to the 18 existing genera. This high taxonomic diversity indicates that the nektonic faunas had already recovered from the end-Permian mass extinction by the beginning of the late Olenekian in the South Kitakami Belt. The ammonoid fauna of the Osawa Formation is similar to that of the late Olenekian of Idaho, North America, and in addition, it has some faunal similarity to those in the western Tethys province. These faunal characteristics are likely to reflect the paleogeographic position of the South Kitakami Belt, which was located at the low-latitude area of the Tethys—Panthalassa border during the Triassic.
Additional Early Triassic (late Olenekian) Ammonoids from the Osawa Formation at Yamaya, Motoyoshi area, South Kitakami Belt, Northeast Japan20, 1(2016); http://dx.doi.org/10.2517/2015PR016View Description Hide DescriptionAbstract.
Two Early Triassic (late Olenekian) ammonoids, Khvalynites sp. and Pseudosageceras multilobatum Noetling, are described from an outcrop of the Osawa Formation at Yamaya in the Motoyoshi area, South Kitakami Belt, Northeast Japan. This is the first report from Japan of the genus Khvalynites and the species Pseudosageceras multilobatum. The ammonoid fauna of the Osawa Formation is diverse and comprises nineteen genera, including two that are undescribed.
Fossil Newhousia imbricata (Dictyotales, Phaeophyceae) from Postglacial Coral Reef Deposits in Tahiti20, 1(2016); http://dx.doi.org/10.2517/2015PR018View Description Hide DescriptionAbstract.
The calcareous brown alga Newhousia imbricata (Dictyotales, Phaeophyceae) was found from postglacial reef deposits collected during Integrated Ocean Drilling Program Expedition 310 from Tahiti. The alga is composed of successive tiers of bilayered laminae, each consisting of a basal cuboid hypodermal cell bearing smaller epidermal cells (one or two in cross-sectional profiles and three or four in long-sectional profiles). The laminae are separated by extracellular cement. Modern N. imbricata is known only from the Hawaiian Islands; this is the first reported occurrence of fossil N. imbricata.
Two Species of Permophricodothyris (Reticularioidea, Brachiopoda) from the Middle Permian, South Kitakami Belt, Japan20, 1(2016); http://dx.doi.org/10.2517/2015PR019View Description Hide DescriptionAbstract.
We describe two species of reticularioid spiriferid brachiopod, Permophricodothyris grandis (Chao) and Permophricodothyris squamularioides (Huang), from the lower part of the Kamiyasse Formation (Wordian), Kamiyasse—Imo area, South Kitakami Belt, northeastern Japan. Permophricodothyris is known from the middle to upper Permian of the Tethyan region, especially from the upper Permian of South China. The two species from the Kamiyasse—Imo area are representative Tethyan elements of the middle Permian brachiopod fauna of the South Kitakami Belt.