2017

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Little is known about the taxonomy of Paleocene ostracodes from ocean drilling sites. Herein, we report 14 ostracode species of the families Eucytheridae, Krithidae, Thaerocytheridae, Trachyleberididae, and Xestoleberididae from Cretaceous-Paleocene sediments at U1407 of Integrated Ocean Drilling Program Expedition 342 off Newfoundland, Northwestern Atlantic. We describe five trachyleberidid species new to science: Croninocythereis clavae sp. nov., Phacorhabdotus flabellicarinus sp. nov., Poseidonamicus norrisi sp. nov., Ryugucivis blumi sp. nov., and Trachyleberidea cronini sp. nov.

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Eight specimens of Sphenodus have been collected from the Upper Cretaceous, Coniacian of Nakagawa Town in Hokkaido, northern Japan. They are referred to as S. cf. lundgreni and Sphenodus spp. 1 and 2, and described in detail. Nearly complete specimens of Sphenodus were previously unknown from the Cretaceous in the Pacific region, and the Nakagawa specimens are the first to exhibit distinct root morphologies, which allow comparison at the species level. A review of the occurrences of this genus reveals that their distribution concentrates in the mid- to high palaeolatitude regions. This distributional pattern of Sphenodus may represent its preference for colder water and possibly explains the extinction of this genus across the Paleocene—Eocene boundary, when the thermal maximum began.

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A new genus of the Corythoecidae (Albaillellaria, Radiolaria) was recovered from the Changhsingian (uppermost Permian) Dalong Formation in Guizhou Province, South China. Qiania Ito and Feng, gen. nov., containing Q. foremanae Ito and Feng, gen. et sp. nov. and Q. uncinata (Rudenko and Panasenko), is characterized by a conical shell consisting of an apical portion and an inflated region with a lateral foramen on the ventral side. The Corythoecidae were thought to range from the Late Devonian to Guadalupian (middle Permian). Therefore, this new find suggests the presence of this family until the latest Permian. Compilation of previous occurrences of corythoecids, in addition to those of Qiania, showed that most corythoecids including Qiania occurred in phosphate-rich facies, and that Qiania occurred in deeper facies than other corythoecids.

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We reinvestigated the standard calcareous nannofossil and diatom biostratigraphy zonations from Deep Sea Drilling Project (DSDP) Leg 41 Holes 366 and 369A in the eastern equatorial Atlantic Ocean in order to determine the geologic ages for the low-latitude diatom zonation. Applying the ages of nannofossil zonations to diatom ones, the ages of several diatom bioevents (first occurrence, FO) which determine the biozones of DSDP Holes 366 and 369A are evaluated as follows; FOs of Baxteriopsis brunii (ca. 38.1 Ma), Coscinodiscus excavatus (ca. 33.6 Ma), Cestodiscus reticulatus (ca. 32.9 Ma), Rocella vigilans (ca. 29.8 Ma), Rossiella symmetrica (ca. 29.5 Ma) and Bogorovia veniamini (ca. 28.3 Ma). These ages may be applicable not only for these holes but also for biostratigraphic studies of other holes which contain Paleogene diatoms. Moreover, this paper describes the taxonomy and stratigraphic ranges of marine diatom Chaetoceros resting spores from DSDP Holes 366 and 369A, including two new morpho-species (Vallodiscus truncatuhis Suto sp. nov. and Xanthioisthmus fortii Suto sp. nov.) and its allied species with synonymy lists, light microscopic observations and several key references for each taxon. As the results of counting of each diatom taxon, it was clear that the sedimentation rate and Chaetoceros resting spore abundances and diversities changed abruptly in the earliest Oligocene (ca. 32 Ma). During the separation of the South American and African continents from the Late Cretaceous to earliest Oligocene, a passage arose that acted for the transfer of Antarctic Bottom Water and modulated the bottom current velocities. The southward bottom water and the passage influenced the sedimentation rate and upwelling of nutrient-rich deeper waters stimulated marine productivity and ecology of Chaetoceros across the late Eocene to early Oligocene.

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As the third installment of our study to describe the cephalopod fauna of the Upper Mississippian Imo Formation, four species of late Chesterian (= Serpukhovian; late early Carboniferous) nautilids are recorded from the dark gray shale of the formation in northwest Arkansas, Midcontinent North America. They include a tainoceratid, Tylonautilus gratiosus (Girty), and three liroceratids, Bistrialites bicostatus (Gordon), Condraoceras? sp. and Peripetoceras kummeli sp. nov. Diagnostic features of P. kummeli separating it from comparable species are its depressed reniform whorl sections with relatively high width/height ratios, large convergent angle of the flanks, and subcentral to subdorsal siphuncular position.

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A well preserved Late Ordovician conodont fauna of 18 species has been recovered from seven limestone samples of the Gongwusu section in the Wuhai area of Inner Mongolia, North China. This conodont fauna is composed of Ansella sp., Belodina monitorensis, Coelocerodontus trigonius, Complexodus sp., Dapsilodus viruensis, Drepanoistodus sp., Gen. et sp. indet, Oslodus semisymmetricus, Panderodus gracilis, Periodon cf. aculeatus, Protopanderodus cf. cooperi, P. varicostatus, Protopanderodus sp., Pseudooneotodus mitratus, Scabbardella altipes, Venoistodus cf. balticus, Yaoxianognathus sp. A, and Yaoxianognathus sp., and shows a mixture of North Atlantic, North China and North American Midcontinent affinities. The presence of Belodina monitorensis, Periodon cf. aculeatus, Protopanderodus varicostatus, Scabbardella altipes and Yaoxianognathus sp. A in the fauna indicates an early Sandbian (late Sa1) age. The fauna is dominated by Periodon cf. aculeatus, Scabbardella altipes and Panderodus gracilis and these together with the occurrence of Protopanderodus species, Drepanoistodus sp. and Ansella sp. characterize the Periodon Biofacies, typical of a deeper water (upper slope) setting. Because of its slope habitat, the Gongwusu fauna differs from the contemporaneous faunas reported from the interior North China Platform, but shows a similarity to the coeval faunas in Baltoscandia, South China and Argentina.

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The ages of the holotype and a referred molar of Elephas maximus buski described by Matsumoto in 1927, and a molar supposedly of the same subspecies described by Makiyama in 1938 from Higashi Betsuin temple in Nagoya, were investigated by AMS (Accelerator Mass Spectrometry) dating. The holotype (IGPS 7266) may date from any of four periods between 1676 and 1941 cal AD, with 1732–1777 cal AD being the most probable (40.7% likelihood). The referred specimen (IGPS 5845) most likely dates from 1784–1796 cal AD (39.4% probability), and the specimen from Higashi Betsuin from 1454–1494 cal AD (52.9% probability). The present specimens, including the holotype are, therefore, not fossils. Historical records show that Asian elephants did not inhabit Japan at these times. These molars must have been imported into Japan in some fashion during historical times and do not represent a subspecies distinct from extant Asian elephants, E. maximus. Although the nominal subspecies E. maximus buski is clearly invalid, it is not clear which of the three extant subspecies of Asian elephant is its senior synonym in this research.

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The extraordinarily large and aberrantly shaped shells of the Permian bivalve family Alatoconchidae (Ambonychioidea), thought to have a photosymbiotic mode of life like the modern fragine bivalve Corculum, are difficult to extract from their host limestone bodies; therefore, their morphologies have been reconstructed mostly based on broken shell pieces. The alatoconchid Shikamaia akasakaensis Ozaki, the type species of the genus from the middle Permian Akasaka Limestone of central Japan, was described based on only three fragmentary specimens; its shell characters were later reassessed from specimens from the Neo area, ca. 30 km NNE of the type locality. Because of the fragmentary nature of the type specimens of S. akasakaensis, this species is difficult to diagnose and cannot be compared taxonomically to the specimens from the Neo area or other known species. A shell reconstruction based on 19 specimens from the type locality shows that S. akasakaensis exhibits a very large, elongated elliptical shell form but clearly differs from the Neo specimens in its higher and longer dorsal crests and more dorsally reflected shell wings in the anterior portion, rendering the establishment of a new species (Shikamaia ozakii Asato and Kase sp. nov.) for the latter specimens. The outer shell consists of a very thin outermost prismatic layer that is underlain by thick layers of granular crystals in both species of Shikamaia, which suggests that the shell did not allow sufficient sunlight penetration to culture symbiotic microbes in the soft tissues of these animals. The “Corculum model” of photosymbiosis therefore is unlikely for the two species of Shikamaia. The discovery of the presence of a ventral gape, a previously unreported shell character, suggests extension of the soft body into the sediment through this opening during life. Three possible modes of life (fragine-like photosymbiosis, lucinid-like chemosymbiosis and normal suspension feeding) are discussed.