Paleontological Research
Volume 12, Issue 1, 2008
Volumes & issues:
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ARTICLES
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The plant fossils from the Kaizara Formation (Callovian, Jurassic) of the Tetori Group in the Izumi district, Fukui Prefecture, Central Japan
View Description Hide DescriptionABSTRACTThe Middle Jurassic (Bathonian to Callovian) Kaizara flora is proposed herein for the plant fossil assemblage in the Kaizara Formation, Kuzuryu Subgroup, Tetori Group. In addition to Otozamites crassipinnatus sp. nov., twelve species are reported, including species of Equisetales, uncertain order of pteridosperms, Cycadeoideales, Cycadales, and Coniferales. Some species have very thick lamina, implying that the climate might include dry periods. All species found in the Kaizara flora are new to the Tetori Group. Therefore, the Tetori-type flora is restricted to post-Callovian stages in the Tetori Group.
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Discovery of mid-Cretaceous ammonoids from the Aridagawa area, Wakayama, southwest Japan
View Description Hide DescriptionABSTRACTMid-Cretaceous ammonoid assemblages are newly identified from four localities in the Aridagawa area, Wakayama, southwest Japan. They consist of Middle to Upper Albian ammonoids such as Desmoceras (Pseudouhligella) dawsoni shikokuense, Puzosia subcorbarica, Mojsisoviczia sp., Oxytropidoceras sp., Mortoniceras sp., etc., and Mantelliceras japonicum, which indicates the Lower Cenomanian stage. The Albian ammonoids were found for the first time from the Chichibu Belt of Kii Peninsula. The discovery of these ammonoids indicates a considerably wide distribution of the mid-Cretaceous deposits in the Aridagawa area, and the necessity of a large revision of the previous stratigraphic division of the Cretaceous strata in the area. The mid-Cretaceous deposits in the Aridagawa area and their abundant molluscan fossils are important for reconstruction of the mid-Cretaceous paleoenvironment and tectonics in the eastern margin of Asia.
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First discovery of a theropod (Dinosauria) from the Upper Jurassic in Mongolia and its stratigraphy
View Description Hide DescriptionABSTRACTA theropod dinosaur is described for the first time from the Upper Jurassic of Mongolia. It is represented by a partial skull from the upper Jurassic Dariv Suite in Dariv, Ikhes Nuur Basin, Gobi-Altai Aimag, western Mongolia, situated relatively close to the Xinjiang Uygur Autonomous Province in the western part of China. From the same beds of the locality, sauropod bones were also abundantly found. Those fossil discoveries suggest that both carnivorous and herbivorous dinosaurs existed in the Jurassic of Mongolia, as in China.
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Permian brachiopods from the Mizukoshi Formation, central Kyushu, SW Japan: Systematics, palaeobiogeography and tectonic implications
View Description Hide DescriptionABSTRACTThis study describes a brachiopod fauna, consisting of 22 species in 19 genera, from the Upper Permian (Lopingian) Mizukoshi Formation in the Mizukoshi area of central Kyushu, southwest Japan. The fauna includes three new species: Anidanthus mizukoshiensis, Terrakea yanagidai and Rhynchopora matsumotoi. The Mizukoshi fauna is a Boreal-Tethyan mixed fauna allied with the Middle Permian brachiopod faunas of central Japan (Hida Gaien Belt), northeast Japan (South Kitakami Belt) and eastern Russia (South Primorye). Palaeobiogeographical data on the Mizukoshi fauna suggest that during the Middle-Late Permian the Mizukoshi area was located between the Hida Gaien region to the north and the South Kitakami region to the south, bordering the eastern margin of North China (Sino-Korea). This conclusion supports a strikeslip model that describes largescale sinistral strikeslip movement along the Tanakura Tectonic Line (TTL)-Median Tectonic Line (MTL) from the Early Cretaceous to Palaeogene.
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Significance of autochthonous fossil barnacles from the Miocene Natori Group at the Moniwa-Goishi area, northeast Japan
View Description Hide DescriptionABSTRACTIn situ fossil barnacle populations (Cirripedia, Balanomorpha) are described from the Miocene Natori Group of the Moniwa-Goishi area, northeast Japan. The Natori Group exhibits a transgressive sequence from subaerial lavas and volcaniclastics (Takadate Formation) to shoreface-shelf deposits (Moniwa and Hatatate formations) in ascending order. In the Takadate Formation, volcaniclastics locally intercalate bay deposits in which the fossil barnacle Balanus bisulcatus occurs on gravel surfaces in situ. The Takadate Formation is unconformably overlain by the basal conglomerate of the Moniwa Formation, which is interpreted as a ravinement deposit formed in an open coast. An extinct barnacle species, Concavus sendaicus, is found as gregarious clusters and solitary individuals on boulder surfaces in the basal conglomerate in situ. These features suggest that B. bisulcatus inhabited in bay environments at the early transgressive stage. On the other hand, C. sendaicus was distributed over open-coast environments during subsequent marine flooding. The in situ C. sendaicus provides strong evidence for the reconstruction of the extinct species habitat.
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Platanoid leaves from Cenomanian to Turonian Mikasa Formation, northern Japan and their mode of occurrence
View Description Hide DescriptionABSTRACTEttingshausenia cuneifolia is reported from the Cenomanian to Turonian Mikasa Formation of central Hokkaido. These leaves occur exclusively in carbonaceous mudstone deposited in either lagoon or marsh. Based on their mode of occurrence, these remnants may have been trapped in the sediments without long prior transport (parautochthonous).
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First discovery of fossil Nautilus pompilius Linnaeus, 1758 (Nautilidae, Cephalopoda) from Pangasinan, northwestern Philippines
View Description Hide DescriptionABSTRACTA chambered nautilus shell from the early Pleistocene deep-water sediments in the Bolinao area of Pangasinan province, northwestern Luzon, Philippines is described. Although the shell is fragmentary, the shell features indicate that the specimen is referable with reservation to the extant Nautilus pompilius Linnaeus, 1758. This finding represents the first and oldest fossil record of N. pompilius and complements the Plio-Pleistocene gap of the nautiloid fossil records. Taphonomic implications for Cenozoic nautiloids were briefly discussed.
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