Paleontological Research
Volume 12, Issue 3, 2008
Volumes & issues:
-
Articles
-
-
Pseudopodial features and feeding behavior of living nassellarians Eucyrtidium hexagonatum Haeckel, Pterocorys zancleus (Müler) and Dictyocodon prometheus Haeckel
View Description Hide DescriptionABSTRACTLight microscopic studies, using both video imaging and normal camera, were made on living nassellarian radiolarians Eucyrtidium hexagonatum Haeckel, Pterocorys zancleus (Müler) and Dictyocodon prometheus Haeckel from the East China Sea off Okinawa Island, Japan. Continuous and careful observations revealed pseudopodial activity related mostly to feeding behavior. The results are presented in detail with the definition of 11 descriptive terms for nassellarian pseudopodia. Among them, terminal projections (TP) extending as straight projections from the aperture of the shell body and forming a conical structure (terminal cone: TC) and axial projections (XP) prolonged outward from the center of the aperture and proximally surrounded by TP are used for feeding. Although there are some minor differences, feeding activities of the three species can be subdivided into the following three cyclic phases; Phase 1 characterized by gradual extension of TP and XP from the aperture, Phase 2 marked by an abrupt withdrawal of TP and XP toward the aperture to engulf captured prey, and Phase 3 during which entangled TP used for capturing prey are completely retracted into the aperture. These lines of evidence suggest that the shell aperture plays the same role of a feeding apparatus as does a mouth. Interestingly, XP of E. hexagonatum sometimes shows abnormal branching, fusion and separation, which is different from the spumellarian axoflagellum.
-
Calcareous nannofossil and planktic foraminiferal biostratigraphy of the Paleogene Iojima Group in the Takashima Coalfield, Nagasaki Prefecture, southwest Japan
View Description Hide DescriptionABSTRACTThe Paleogene Iojima Group is exposed in the Takashima coalfield of northwestern Kyushu, southwest Japan. The group is divided into four formations: the Okinoshima, Magome, Funazu, and Daimyoji formations (in ascending stratigraphic order). Among these strata, mudstone and muddy sandstone of the Okinoshima and Funazu formations contain a number of common age-diagnostic calcareous microfossils, nannofossils, and planktic foraminifers.
Our biostratigraphic study of the Paleogene Iojima Group indicates that the Okinoshima Formation corresponds to calcareous nannofossil Zone CP14 and planktic foraminiferal Zones E10-E13; the Funazu Formation is assigned to Zones CP14-CP16. The Okinoshima and Funazu formations are assigned to the late middle Eocene and late middle Eocene to early Oligocene, respectively, suggesting that 1) the Okinoshiman molluscan Stage correlates with the middle Eocene, as proposed in previous studies; and 2) the Magome Formation, which includes coal-bearing strata, correlates with the Onga marine regression.
-
Late Paleozoic and Mesozoic foraminifers contained in limestone fragments of the Kamade Breccia of the Upper Cretaceous Aioi Group from Kamade, northeastern part of Aioi, Hyogo, Japan
View Description Hide DescriptionABSTRACTAge distribution and provenance of limestone fragments contained in the Kamade Breccia of the Upper Cretaceous Aioi Group, distributed in the western part of Hyogo prefecture, Japan were considered. Among 67 samples examined, 19 are Carboniferous (Serpukhovian to Gzhelian), 20 are Permian (Sakmarian to Capitanian), and two are Triassic (early Anisian). Two samples of conglomeratic limestone contain both Carboniferous and Permian foraminifers. The ages of the other 28 samples are indeterminable. Of these 28, four are assumed to be post-Triassic. Carboniferous and Permian limestone fragments and a subduction-related broken limestone pebble of unknown age are concluded to have been derived from the Akiyoshi Terrane, and early Anisian ones from the Maizuru Terrane. The source of the post-Triassic boulders and cobbles consisting of very fine-grained lime-mudstone cannot be determined because there is no plausible limestone in Japan from which they could have been derived. Systematically described fusulinoideans comprise seven species of ozawainellids, fusulinids, and schwagerinids. They are Eostaffella kanmerai, Eostaffella yowarensis, Pseudofusulinella itoi, Rauserites stuckenbergi, Schwageriniformis schwageriniformis, Triticites simplex and Paraschwagerina sp. This paper is the latest in a series of works whose aim is a complete description of the Hyogo foraminifera.
-
Permian ammonoid Kufengoceras from the uppermost Maokou Formation (earliest Wuchiapingian) at Penglaitan, Laibin Area, Guangxi Autonomous Region, South China
View Description Hide DescriptionABSTRACTTwo Permian ammonoid specimens belonging to the genus Kufengoceras are described from the topmost bed of the Laibin Limestone, Guangxi, South China. The ammonoid horizon is just above the Global Stratotype Section and Point for the Guadalupian/Lopingian Boundary. Kufengoceras is a typical Middle Permian ammonoid, and its occurrence above the GSSP supports the previous opinion that the ammonoid faunal changeover took place slightly after the beginning of the Lopingian.
-
Late Jurassic to Early Cretaceous ammonite fauna from the Somanakamura Group in Northeast Japan
View Description Hide DescriptionABSTRACTOver 300 specimens of ammonites of Late Jurassic to Early Cretaceous age were collected by the members of local fossil research associations from various localities in the Soma area, Northeast Japan. The new collection of ammonites is confined to two formations, Nakanosawa Formation in the lower and Koyamada Formation in the upper part of the Somanakamura Group. Four ammonite-bearing levels (A2 to A5) are ascertained in these formations, and each level was dated by the ammonites discovered. The lower three levels (A2, A3 and A4) are contained in the Nakanosawa Formation. The newly collected ammonites from this formation include a well preserved adult specimen of Aulacosphinctoides tairai sp. nov., relatively well preserved specimens of Subdichotomoceras chisatoi sp. nov., hitherto unknown Haploceras sp. and Hybonoticeras sp., besides many already known species. The lowest level A2 represents a certain age within the Kimmeridgian - early Tithonian. The next lower, A3, somewhat later than the former, is correlated to the late Kimmeridgian to early Tithonian, and the upper level, A4, to the Tithonian. The Nakanosawa fauna indicates therefore the Kimmeridgian to Tithonian interval as a whole. The ammonites from the Koyamada Formation, known only from the uppermost level A5, include a new species of Dalmasiceras muneoi, besides other berriasellids and neocomitids. The age of the formation is Berriasian. The ages hitherto assigned are not greatly modified by the new discoveries. Descriptions of the new species and some other interesting species are given in this paper.
-
The impact of fish farming and bank construction on Ostracoda in Uranouchi Bay on the Pacific coast of southwest Japan-Faunal changes between 1954 and 2002/2005
View Description Hide DescriptionABSTRACTUranouchi Bay, an enclosed bay in the southern part of Shikoku Island, southwest Japan, has a complicated geography, being long and narrow with some small inlets. Since 1955, it has been influenced by organic pollution from fish farming. In the spring of 1954, many surface sediment samples were collected in the bay, and were then studied by Ishizaki (1968) to examine ostracode thanatocoenoses. Comparison with this earlier work allows us to investigate faunal changes over this approximately 50-year period. We collected surface sediment and seaweed samples in the bay for ostracode analysis in 2002 and 2005. A total of 124 species were obtained from 29 samples. Comparison between the results suggests that ostracodes have decreased in number in the inner part of the bay and increased greatly in the middle and outer parts of the bay. The number of species and the species diversity has also increased in the middle and outer parts of the bay. Mud dwellers have mostly disappeared from the inner bay and are now found in small inlets in the middle and outer parts of the bay. These changes are caused by the enlargement of areas of anoxic or oxygen-poor bottom waters in the inner part of the bay during the summer. This summer hypoxia is thought to have been brought on by organic pollution from fish farms and the complicated geographical features of the bay. The decrease of inflows of coarse-grained sandy sediments from the outside of the bay, resulting from the intermittent construction of artificial concrete banks in the mouth of the bay in 19461950, 19691974 and 19911996, induced the emergence of preferable environments for a variety of bay and phytal ostracodes in the middle and outer parts of the bay. Valves of phytal species such as xestoleberidid and paradoxostomatid ostracodes increased greatly in the muddy bottoms of the middle part of the bay, where many artificial floating rafts for fish farms are distributed. Seaweed has grown on submerged parts of the floating materials, providing new habitats for phytal ostracodes.
-
-
Short Notes
-
-
New record of a rhyncholite (cephalopod upper jaw element) from the Maastrichtian of Hokkaido, Japan
View Description Hide Description
-