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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.
Redescription of Two Krithid Species (Crustacea, Ostracoda) from the Sea of Japan, with a Comment on the Taxonomic Characters of Krithidae20, 1(2016); http://dx.doi.org/10.2517/2015PR022View Description Hide DescriptionAbstract.
The marine podocopid ostracod Krithe antisawanensis is redescribed on the basis of its appendages and the carapaces of adult male and female specimens. The krithid species Parakrithella pseudadonta, which has only been previously described on the basis of the carapace morphology and male appendages excluding the copulatory organ, is redescribed here with its female appendages and male copulatory organ. Both krithid genera (Krithe and Parakrithella) have three articulated podomeres in the fifth and sixth limbs and an axe-head anterior vestibulum. Such characters are useful as diagnostic features for the family.
Spathian (Late Olenekian, Early Triassic) Ammonoids from the Artyom Area, South Primorye, Russian Far East and Implications for the Timing of the Recovery of the Oceanic Environment20, 1(2016); http://dx.doi.org/10.2517/2015PR023View Description Hide DescriptionAbstract.
Five Spathian (late Olenekian) ammonoids are newly reported from the Zhitkov Formation in the Artyom section, South Primorye, Russian Far East. They include the early Spathian taxa Bittnerites pacificus and Tirolites longilobatus from the middle part of the formation, and Ussuriphyllites amurensis, Leiophyllites sp. and Keyserlingites sp. from the upper part. The Ussuriphyllites amurensis Zone was previously correlated with the lower Anisian, but we herein correlate it with the upper Spathian. As a consequence of this age assignment, the weakly bioturbated offshore mudstone in the middle and upper parts of the formation is correlated with the Spathian. In contrast, the Smithian (early Olenekian) offshore laminated mudstone in the lower part of the formation lacks any sign of bioturbation. These mudstones suggest that the oxygen-deficient sea floor was transformed into an aerobic environment inhabitable to benthic organisms at the Smithian-Spathian boundary.
Non-Marine Bivalve Trigonioides (Trigonioides) quadratus from the Cretaceous Strata of the Lhasa Block, Tibet, and Its Biostratigraphic Implications20, 1(2016); http://dx.doi.org/10.2517/2015PR025View Description Hide DescriptionAbstract.
In this study, we describe a new occurrence of the well preserved freshwater bivalve Trigonioides (Trigonioides) quadratus from Lazha, Baingoin County, Tibet. It suggests an Early Cretaceous (Aptian—Albian, most likely Aptian) age for the fossil-yielding sediments, which can now be correlated to the Duoba Formation (equal to the lower part of the Langshan Formation) in Xainza. Our study suggests that this fossil-bearing volcano-sedimentary succession should be assigned to the Lower Cretaceous Zenong Group instead of the uppermost Cretaceous—Paleogene “Linzizong Group” as previously thought. We propose that the distribution of the Linzizong Group needs to be further investigated and the geological map of the Lhasa Block further refined. Our study provides some new information for understanding the spatial and temporal distribution of basins in the Lhasa Terrane, and highlights the need of more biostratigraphic studies in the region, which may provide critical constraints on the process and pattern of the northward subduction of the Neotethyan oceanic slab beneath South Asia since the onset of the Indo-Asian collision.
Coiled Nautiloids from the Lower Carboniferous Fayetteville Formation in Arkansas, Midcontinent North America20, 1(2016); http://dx.doi.org/10.2517/2015PR017View Description Hide DescriptionAbstract.
As the first installment of our study to clarify the cephalopod fauna of the Fayetteville Formation (lower Carboniferous; middle Chesterian) in northwest to north-central Arkansas, Midcontinent North America, eight species of coiled nautiloids are described from the lower and upper shale units. They include a tainoceratid, Tylonautilus gratiosus (Girty), the koninckioceratids, Endolobus clorensis Collinson, E. sp., Valhallites tuberculatus sp. nov. and V. westforkensis sp. nov., a trigonoceratid, Epistroboceras mangeri sp. nov., and the liroceratids, Liroceras? sp. and Bistrialites bicostatus (Gordon). Only T. gratiosus and B. bicostatus survived into the late Chesterian. Embryonic to early juvenile shell morphologies of T. gratiosus are revealed and suggest close phylogenetic relationships between this genus and the trigonoceratid genera. Morphologies of new material of B. bicostatus warrant the present new combination for this species, which was questionably placed in Liroceras by Gordon in 1964.
19, 4(2015); http://dx.doi.org/10.2517/2015PR010View Description Hide DescriptionAbstract.
A thylacocephalan fauna from the upper Olenekian (Lower Triassic) Osawa Formation in the South Kitakami Belt, Northeast Japan, is described. The fauna comprises three species belonging to three genera: Ankitokazocaris bandoi Ehiro and Kato sp. nov., Kitakamicaris utatsuensis Ehiro and Kato gen. et sp. nov., and Ostenocaris sp. This is the first report of fossils belonging to the class Thylacocephala from Japan, and it expands their paleogeographic distribution. As almost all genera of Thylacocephala inhabited low-latitude areas in each relevant geological time, their occurrence from the Osawa Formation supports previous opinions that the South Kitakami Belt was located in the equatorial region during the Triassic.
A Rectifying Effect by Internal Structures for Passive Feeding Flows in a Concavo-Convex Productide Brachiopod19, 4(2015); http://dx.doi.org/10.2517/2015PR011View Description Hide DescriptionAbstract.
It has been experimentally shown that the shell morphology of concavo-convex productide brachiopods has the potential to generate passive flows for feeding. However, there still remains the problem of how the presence of internal soft parts influences the course and pattern of the flows. To clarify the effect of soft parts, we performed additional experiments of fluid visualisation using a flow tank and a transparent, polyhedral model with supposed soft parts in a postero-median region. Regardless of the ambient flow directions, the experimental results showed that inflows through ear gapes turned into symmetrical vortices inside the model. The soft parts altered the course of internal flows and interfered with the vortices entering the median region. Therefore, stepwise inflows pushed the precedent vortices forward as the rotational speed decreased. As a result, the slower vortices aligned with the brachial ridges on which the lophophore was arranged. Morphologically, productide brachial ridges tend to lie in the antero-lateral corners of the dorsal disc. The rectifying effect by means of soft parts, though consequential, would enable productides to sieve food particles from gentle vortices rather than from swift vortices just after the inflow through the ear gapes.
19, 4(2015); http://dx.doi.org/10.2517/2015PR008View Description Hide DescriptionAbstract.
Two species of Darriwilian (late Middle Ordovician) nautiloid cephalopods are described from the Wunbye Formation and its equivalent strata in the Shan Plateau of Myanmar (Sibumasu Block). They are the orthocerid Sibumasuoceras langkawiense (Kobayashi) and the discosorid Tasmanoceras sp. First, Sibumasuoceras is proposed for a new genus of the cayutoceratin pseudorthoceratids. Sibumasuoceras langkawiense [originally Ormoceras langkawiense, the type species of the genus] was previously assigned either to the Actinocerida or the Discosorida. However, the present investigations reveal that it possesses thin connecting rings and differentiated endosiphuncular deposits and lacks a detailed endosiphuncular canal system, all suggestive of a relationship to the Orthocerida. Sibumasuoceras is known to occur so far from Malaysia and Myanmar of the Sibumasu Block, which was part of northern Gondwana during the early Palaeozoic. Second, the rare genus Tasmanoceras, which was previously known only in Tasmania, is confirmed in Southeast Asia for the first time; this implies an Ordovician marine biotic linkage between Sibumasu and Tasmania over northern Gondwana.