The Hina Limestone yields abundant conodont elements that range from early Visean to late Bashkirian in age. These conodont faunas permit detailed examination of the successive changes across the Mid-Carboniferous boundary. Six conodont zones can be recognized in ascending order : the Gnathodus bilineatus, Declinognathodus inaequalis-Gnathodus bilineatus, Declinognathodus noduliferus, Neolochriea nagatoensis, Neolochriea koikei, and Neognathodus symmetricus Zones. The Mid-Carboniferous boundary in the Hina Limestone can be identified by the base of the Declinognathodus inaequalis-Gnathodus bilineatus Zone. A remarkable faunal transition occurs within the Declinognathodus inaequalis-Gnathodus bilineatus and Declinognathodus noduliferus Zones, in which Mississippian conodonts go extinct and several new typical Pennsylvanian taxa appear. Three Declinognathodus species, Declinognathodus inaequalis, D. noduliferus, and D. japonicus, successively appear in the order given. A new genus, Neolochriea, with Neolochriea hisaharui, sp. nov. as the type species and two other new species, N. hisayoshii and N. koikei, are described in addition to eight other species of conodonts. All Neolochriea species occur in the stratigraphic level between the extinction of Mississippian conodonts and the appearance of Neognathodus symmetricus.

View full abstract

Seasonal patterns of shell microincrement growth in a venerid bivalve Phacosoma japonicum were analyzed for the three populations from Hakodate, Ariake, and Kagoshima Bays around the Japanese coasts. The northemmost Hakodate population in Hokkaido grew rapidly in a limited interval between late spring and summer. The number of microincrements within an annual increment in the specimens from this population was smallest (200-250 increments) among the three samples of populations examined, and each microincrement width was largest (0.25-0.3mm) at the central part of an annual increment. By contrast, in the southemmost Kagoshima population in southern Kyushu, shell growth occurred slowly in a long term between early spring and fall. The specimens forming this population are characterized by having the narrowest microincrements (each 0.10-0.12mm) and largest number of microincrements in the annual increment (300-350 increments). In this species, it has been confirmed that the growing season reflects the seasonal changes of phytoplankton abundance. The phytoplankton bloom usually occurs in spring in embayments of northern Japan and in summer in those of central and southern Japan. In Ariake Bay (central Kyushu), however, the phytoplankton becomes most abundant in winter and remains at low levels in the other seasons. The Ariake population of P. japonicum showed the most active growth in intervals between winter and early spring. In this sample, the microincrement width attained a maximum in the earlier portion of each annual increment, and the annual increment showed a particularly right-skewed pattern which reflects the winter phytoplankton bloom in this bay.

View full abstract

A new anascan cheilostome bryozoan species, Dysnoetocella? voigti, is described from the Upper Cretaceous Izumi Group in the northwestern part of Shikoku Island, Japan. The zoarium is erect and unjointed, with subcylindrical multilamellar branches. Three types of fine structure are evident in the calcareous skeletal layers from well preserved specimens. The narrow frontal shields of the zooids show ontogenetic thickening, which suggests that the species is an anascan cryptocystidean. The zoarium, consisting of many zooid columns, is reminiscent of some Paleozoic trepostomes. Although the zooid column is sometimes found in the Ascophora, it also occurs rarely in the Anasca.

View full abstract

Fourteen species of Neptunea are listed from the Pliocene and lower Pleistocene of the Japan Sea borderland. Among them, Neptunea (Neptunea) eos (Kuroda), N. (N.) hataii Noda, and N. (Golikovia) nikkoensis Nomura are extinct. These species and a part of the N. polycostata stock in the Japan Sea suffered extinction before the end of the early Pleistocene. However, the N. polycostata stock survived in the Okhotsk and Bering Seas. On the other hand, N. intersculpta (Sowerby) and N. (Barbitonia) arthritica (Bernardi) are still living in the Japan Sea. This contrast is due to the Plio-Pleistocene records on the Pacific side and eurythermal ecology of N. intersculpta and N. arthritica.

View full abstract

Two species of permianellid brachiopods, Permianella typica He and Zhu and Laterispina parallela Shen, Fan, Zhang and Zhang, are described from the Middle Permian (Kubergandian) Kanokura Formation of the Southern Kitakami Mountains, Northeast Japan. This is the first description of permianellids from the Japanese Permian.

View full abstract

Factor analysis of planktic foraminiferal assemblages analyzed in sediment samples from the Northwest Pacific Ocean near Japan defines five major factors including the Kuroshio, Transitional Water, Oyashio, Kuroshio Gyre Margin and Coastal Water factors which, when mapped, show distinctive distributions. These factors account for over 94% of the total variance. Each of the factors can be treated as an independent variable in a regression analysis. Equations relating factors to winter and summer sea-surface temperatures (SSTs) show a high degree of accuracy. The standard errors of estimate for the transfer function equations PFJ-125 established in this study average about ±1.75°C for estimated winter temperatures, and about ±1.17°C for summer temperatures. Transfer functions PFJ-125 were applied to assemblages representing the last 12K yrs. in piston core C-1 collected in the area off Joban, northeast Honshu, Japan. The lowest estimated winter SST is 4.1°C and 18.5°C for the summer SST at 10, 500 yrs. B. P. whereas at 6, 300 yrs. B. P. the winter highest SST is 12.8°C and 23.9°C in the summer. Based on down-core variations in estimated winter and summer SST and fluctuations of the five identified factor loadings, the C-1 core site was alternatively under the influence of the Oyashio and Kuroshio Fronts through the last 12 K yrs. Marine conditions at core site C-1 at 10, 500 yrs. B. P. are comparable with those recorded in the same area for the last glacial maximum.

View full abstract

A mammalian tooth from the lower Middle Miocene Korematsu Formation (ca. 16.3-15.6 Ma) within the Bihoku Group in Shobara City, Hiroshima Prefecture, southwestern Japan, is described and identified as a right upper first molar of the amphicyonid carnivore Ysengrinia sp. This is the first amphicyonid to be described from Far East Asia and it provides additional evidence for the carnivoran faunal connections between Europe-Asia-North America during the Early and early Middle Miocene.

View full abstract

The species Equus nipponicus Shikama and Onuki is a true horse, possibly even a domestic animal, not an Asiatic wild ass. It has been dated to 1, 530±60 years B. P.

View full abstract