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January 2011 - present
Publications
Publications (48)
Seven isolated eggshell fragments and six eggshell impressions were collected from the Okurodani Formation (Hauterivian to Barremian) in Shokawa, Takayama City, Gifu Prefecture, Japan. To date, these specimens represent the oldest fossil eggshells in the country. Microscopic observations classified the eggshells into Testudoolithidae indet., Ramopr...
An isolated theropod tooth was found in the HauterivianBarremian Itsuki Formation of the Tetori Group in the Kuzuryu district, Ono City, Fukui Prefecture, central Japan. The present specimen, OMFJ V-1, shows a thick lanceolate basal cross-section and small mesial and distal denticles. A cladistic analysis based on the dental characters suggested th...
This paper describes Ctenoides cf. subrapa (Nagao, 1934) from the Lower Cretaceous Toriakeura Formation of the Choshi Group collected from Nagasaki-cho, Choshi City, Chiba Prefecture in central Honshu, Japan. The present specimens closely resemble Ctenoides subrapa (Nagao, 1934) described from the Lower Cretaceous Miyako Group in northern Honshu. T...
We report a fossil record of Procellariidae from the Ichijiku Formation (Middle Pleistocene), Kimitsu City in Chiba Prefecture, Japan. Although this specimen is a partial sternum, we assign it to Procellariidae based on several of its osteological characteristics, such as the size, shape of the linea intermuscularis, and aspect ratio of the incisur...
Twelve species of small gastropods are extracted using the sodium tetraphenylborate method from the strongly lithified shallow marine deposits of the Barremian (Lower Cretaceous) Kimigahama Formation of the Choshi Group, central Japan. They belong to the following families and subfamilies; Eudaroniidae, Pseudomelaniidae, Ampezzopleurinae, Metacerit...
Fossil turtles, specimens in total, including isolated shells and limb bones, are reported from the Lower Cretaceous Tetori Group of localities of Ono City, Fukui Prefecture, central Japan. This chelonian assembledge includes Manchurochelys sp., an indetermined taxon of the Xinjiangchelyidae, and a basal Trionychia. e genus Manchurochelys was hithe...
Bedforms related to supercritical flows and hydraulic jumps have been increasingly recognized in various depositional environments. However, few ancient examples have been investigated in terms of the variations and transitions of supercritical-flow deposits. We present a detailed analysis of the sedimentary facies and stacking patterns of cyclic s...
A new species of the genus Wareniconcha, W. mercenarioides, belonging to the chemosymbiotic bivalve subfamily Pliocardiinae (family Vesicomyidae), is described from a Pliocene methane-seep deposit at Liog-Liog on Leyte Island, Philippines. With a length of almost 12 cm, this species is significantly larger than the six extant species currently cons...
This paper describes the stratigraphy and biofacies of the Lower Cretaceous Kuwajima Formation, a member of the Itoshiro Subgroup of the Tetori Group in the Setono area, Ishikawa Prefecture, Central Japan. This formation is approximately 140 m in thickness and comprises brackish sandy siltstones containing the brackish bivalve Myrene tetoriensis in...
We report on the first known occurrences of earliest Cretaceous belemnites in Japan, including: Cylindroteuthis aff. knoxvillensis Anderson (Cylindroteuthididae) from the Mitarai Formation (Berriasian) of the Tetori Group in the Shokawa area, Gifu Prefecture, central Japan; and Hibolithes spp. (Mesohibolitidae) from the Isokusa Formation (Berriasia...
Molluscan larval shells are described from the upper Carboniferous (Moscovian) Ichinotani Forma-tion at Fukuji, Okuhida-onsen-gou, Takayama City, Gifu Prefecture, Japan. The vast majority of these larval shells are isolated and not metamorphosed. The larvae appear to represent species with planktotrophic larval development representing pseudozygopl...
This paper reports on latest Late Jurassic to early Late Cretaceous radiolarians extracted from a gravel of calcareous nodule that originated from the basal conglomerate of the Pliocene Naarai Formation. The calcareous nodule (ca. 12 cm in length) contains vertebrate bones, and lithologically similar gravels have been known to contain Albian and Ti...
Kappachelys okurai gen. et sp. nov. is named and described based on two isolated carapacial elements (right
seventh costal and left seventh peripheral) from the Lower Cretaceous (?upper Neocomian) Akaiwa Formation of west-central Honshu, Japan. Kappachelys is a small turtle (shell length *10 cm) that exhibits a unique combination of three features:...
Kappachelys okurai gen. et sp. nov. is named and described based on two isolated carapacial elements (right seventh costal and left seventh peripheral) from the Lower Cretaceous (?upper Neocomian) Akaiwa Formation of west-central Honshu, Japan. Kappachelys is a small turtle (shell length *10 cm) that exhibits a unique combination of three features:...
Five species of pulmonate gastropods are described from the fluvial deposits of the Early Cretaceous Kuwajima Formation (Tetori Group) of Shiramine district, Hakusan City, Ishikawa Prefecture, central Japan. Gyraulus sp., Aplexa kasekikabe sp. nov. and Zaptychius kuwajimaensis sp. nov. appear to be inhabitants of the marginal zone in shallow lakes....
A fossil pearl from the Upper Miocene Kubota Formation in the Higashitanagura area, Fukushima Prefecture, northeastern Japan is described. The pearl is spherical in shape and made up of layers of regularly foliated or crossed foliated structure composed of thin lamellar crystallites. It also contains a lenticular sublayer of prismatic structure com...
A total of 125 specimens of fossil turtles are have been unearthed since 1999 from the middle Pleistocene Kiyokawa Formation of the Shimosa Group at Yoshinoda, Sodegaura City, Chiba Prefecture, Central Japan. Of these, well-preserved 40 specimens are allocated into two extinct taxa of the family Geoemydidae; 25 as Ocadia nipponica and 15 as Mauremy...
Chelonian eggshell fossils from the Lower Cretaceous Kuwajima Formation of the Tetori Group are described. The eggs were originally spherical or ellipsoidal in shape. The eggshells consist of a single layer of spherulitic shell units composed of needle-like crystallites originating from a nucleation center. This corresponds to modern rigid-shelled...
A fossil delphinid was recovered from the middle Pleistocene Ichijuku Formation，Kazusa Group，Chiba Prefecture，Japan．The specimen consists of an incomplete right mandible．It is a part of the horizontal ramus having at least 20 alveoli．The general outline of the horizontal ramus and number of alveoli represent a close affinity to Delphinidae，especial...
We describe here one of the oldest known Japanese mammals, a triconodont lower jaw from the Early Cretaceous Kuwajima Formation, Tetori Group, Japan. This mammal is recognized as the type of Hakusanodon archaeus, new genus, new species, and as closely related to Eurasian and North American Jurassic “amphilestid” triconodonts (Simpson 1925b–c; Jenki...
Platynotan lizards underwent a dramatic Late Cretaceous radiation into marine habitats. Beginning with small-bodied forms, the lineage culminated with the mosasaurs, large predatory lizards with a world-wide distribution in the Santonian–Campanian. Moreover, the marine squamate radiations of the Cenomanian–Turonian are remarkable in having produced...
千葉県袖ケ浦市吉野田に分布する下総層群清川層の氾濫原堆積物から, 淡水生貝類化石群が発見された. 化石群は, マメタニシParafossarulus manchouricus, ヒラマキミズマイマイ近似種Gyraulus cf. chinensis, モノアラガイ類Lymnaeidae gen. et sp. indet., イシガイUnio douglasiae, ドブガイ類Anodonta cf. woodiana, マシジミCorbicula leanaから構成される. 塊状シルト層から産出する二枚貝化石は通常合弁で, しばしば生息姿勢を示し, 原地性もしくは準原地性の化石群と認定されることから, 多様な貝類群集が繁殖できる安定した止水域 (湖沼) が, 河川の氾濫原に存在したと考えら...
The bone-bearing beds of the Lower Cretaceous Kuwajima Formation (Tetori Group) are described. Three facies of bone-bearing beds (Facies I: carbonaceous sandstones; Facies II: dark grey fine-grained silty sandstones; Facies III: dark greenish-grey mudstones) are present in inter-channel deposits that originated on a floodplain. The grain size of th...
We describe a new spalacotheriid (acute-angled) "symmetrodont" (Mammalia, Trechnotheria), Symmetrolestes parvus gen. et sp. nov., from the Lower Cretaceous, likely Barremian, Kitadani Formation of the Tetori Group, central Japan. The specimen consists of a fragmentary right lower jaw with first incisor and five preserved postcanine teeth (interpret...
Sauropod dinosaurs are poorly represented in the Lower Cretaceous of eastern Asia. Here, we describe a number of isolated sauropod teeth from the Kuwajima Formation (?Berriasian–?Hauterivian) of Shiramine, Japan. The mosaic of shared derived characters and symplesiomorphies displayed by the teeth indicate that they are referable to a basal member o...
The ultrastructure of the muscle-shell attachment in the embryo and adult specimens of Nautilus pompilius Linnaeus, 1758, was investigated by optical and transmission electron microscopy. In adult specimens, myoadhesive mantle epithelial cells at the attachment site of the retractor muscle are high columnar and characterized by elongate microvilli...
A new dinosaur track locality was discovered in the upper reaches of Mekko-dani ravine, Okuchi Village, Ishikawa Prefecture, Japan, where deposits of the ltoshiro and Akaiwa Subgroups, Tetor iGroup are distributed. The localitv is included in the Neocomian Kuwajima Formation, Itoshiro Subgroup, and the depositional facies indicates a paleo-environm...
Iridophores are widely distributed in the animal kingdom. In bivalves, iridophores occur in photo-symbiotic species belonging to the subfamilies Fraginae and Tridacninae. This paper describes the fine structure and distribution of iridophores in species of Fraginae by light and electron microscopy. Each iridophore consists of alternating layers of...
更新統下総層群上泉層にはギルバート型粗粒三角州が認められる.この三角州前置層の大規模フォーセット層理ごとに, 内部堆積構造や古流向, 粒度組成や含まれる貝化石群集などの解析を行った.その結果, フォーセット層理の内部堆積構造に"バックセット層理"が含まれることが明らかになった.ここでは前置面での混濁流の流下によって形成された平行層理相と高流砂階のシュートとプールが前置面を上流側に移動することによって形成されたと考えられるバックセット層理相の繰り返しがみられる.この内部堆積構造とその組成(粒度や貝化石群集)には明瞭な相関が認められ, 組成からも形成過程の違いが特徴づけられる.このようなギルバート型粗粒型三角州の発達は調査地点が河口にやや深い水深があり, 粗粒な堆積物が安定して供給されるなどの古...
Luo1 suggests that the vertebrate fauna from the Yixian Formation
(Liaoning Province, China) shows that this region of eastern Asia was a refugium,
in which several typically Late Jurassic lineages (compsognathid theropod
dinosaurs, 'rhamphorhynchoid' pterosaurs, primitive mammals) survived
into the Early Cretaceous1 (Fig. 1). Data
from slightly ol...
Luo suggests that the vertebrate fauna from the Yixian Formation
(Liaoning Province, China) shows that this region of eastern Asia was a
refugium, in which several typically Late Jurassic lineages
(compsognathid theropod dinosaurs, `rhamphorhynchoid' pterosaurs,
primitive mammals) survived into the Early Cretaceous ( Fig. 1 ). Data from slightly ol...
A predominantly microvertebrate assemblage from the Tetori Group (Lower Cretaceous) of central Honshu is described. The fauna consists of many hundreds of vertebrate fossils which represent a diverse terrestrial/non-marine fauna. Taxa present include fish, reptiles, amphibians and birds. The preservation of the fossils is generally good, although t...
