Hobetsu Museum

Hokkaido, Japan

Hobetsu Museum

Hokkaido, Japan

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Fuchs D.,Free University of Berlin | Iba Y.,Hokkaido University | Ifrim C.,University of Heidelberg | Nishimura T.,Hobetsu Museum | And 4 more authors.
Palaeontology | Year: 2013

The phylogenetic origin and the timing of origination of the Decabrachia are controversial. This is due to a poor understanding of character complexes relating to the shell, which causes difficulties in establishing homologies among different taxa. One central problem concerns a clear differentiation between belemnoids and early spirulids. A comparative analysis of shell structures of well-preserved specimens including types and new material of Cretaceous spirulids Groenlandibelus, Naefia and Cyrtobelus, as well as selected taxa of aulacocerid, belemnitid and diplobelid belemnoids, revealed a set of 14 characters. Seven characters (apical angle, chamber length, dorsal and ventral sutures, orientation of septa, direction of the dorsal part of the septal neck, primordial rostrum) are not or less diagnostic, whereas the seven remaining characters can be reliably used to distinguish between the Decabrachia on the one hand and Belemnitida and Aulacocerida on the other hand. These diagnostic characters are as follows: (1) presence/absence of a mural flap; (2) position of the siphuncle; (3) shape of the dorsal soft tissue attachment scar; (4) presence/absence of tabular nacre in the conotheca; (5) presence/absence of a rostrum proper; (6) presence/absence of a narrow rod-like proostracum; and (7) presence/absence of a caecum. Diplobelida and 'Naefia' matsumotoi, however, exhibit a mosaic of decabrachian and belemnoid characters. Owing to striking differences between N. neogaiea, the type species of Naefia, and 'N.' matsumotoi, the new genus Longibelus has been erected. Besides a redescription of Longibelus ('Naefia') matsumotoi, we describe the first Maastrichtian occurrences of this species from Hokkaido (northern Japan) and Alaska. Among the type material of N. neogaiea from the Maastrichtian of Chile, we found one specimen that unambiguously belongs to Longibelus gen. nov. Similarly, two specimens from the Maastrichtian of Mexico previously determined as N. neogaiea also belong to the new genus. Also, we can reinterpret material from the Cenomanian of India as Longibelus gen. nov. New material from the Albian of India likewise assignable to Longibelus is described for the first time. Finally, we introduce the first records of coleoids from Zululand (South Africa). These specimens belong to Longibelus as do specimens from the Aptian of Caucasus (previously described as 'Naefia' kabanovi). A phylogenetic approach suggests that Longibelus gen. nov. is derived from diplobelid-like belemnoids and gave rise for the Decabrachia or at least groenlandibelid spirulids. This strongly supports earlier ideas on a close relationship between Cretaceous Decabrachia and belemnites and simultaneously challenges opinions that Decabrachia originated in the Carboniferous. © The Palaeontological Association.


Tanaka G.,Gunma Museum of Natural History | Ono T.,1552 141 Honden | Nishimura T.,Hobetsu Museum | Maeda H.,Kyoto University
Paleontological Research | Year: 2013

Samples of Middle Permian organic-rich black unconsolidated mud were collected from a fissure of black limestone in Kinshozan Mountain, Akasaka City, Gifu Prefecture, central Japan. Nine new species, one new genus and one new family are described herein: Ikeyaparchitidae Tanaka fam. nov., Gifuaparchites Tanaka and Maeda gen. nov., Aurikirkbya kinshozanensis Tanaka sp. nov., Gifuaparchites takagii Tanaka and Maeda sp. nov., Cavellina hashintotoi Tanaka and Maeda sp. nov., Bairdia nishiwakii Tanaka and Nishimura sp. nov., Bairdia akasakaensis Tanaka sp. nov., Bairdia oogakiensis Tanaka sp. nov., Bairdiacypris? hayasakai Tanaka sp. nov., Acratia? okumurai Tanaka sp. nov., and Acratia? hamadai Tanaka, Ono and Maeda sp. nov. This is the first report from Japan of a typical Panthalassa ostracod assemblage during the Middle Permian, and of which is characterized by typically endemic species. © by the Palaeontological Society of Japan.


Shigeta Y.,National Museum of Nature and Science | Nishimura T.,Hobetsu Museum
Paleontological Research | Year: 2013

Gaudryceras hobetsense sp. nov. is described from the Nostoceras hetonaiense Zone (= lowest Maastrichtian) of the Hobetsu area, south-central Hokkaido, Northern Japan. Its shell is characterized by fine lirae on early whorls, distant rounded or flat-topped, narrow band-like ribs on middle and later whorls, and frequent collar-like ribs on later whorls. The occurrence of this new species strongly suggests the presence of lowest Maastrichtian strata in southern Alaska, and sheds light on the age delineation of the chronologically poorly defined beds in northern and eastern Hokkaido. © by the Palaeontological Society of Japan.


Shigeta Y.,National Museum of Nature and Science | Nishimura T.,Hobetsu Museum
Paleontological Research | Year: 2013

A new Cretaceous heteromorph ammonoid, Phylloptychoceras horitai sp. nov., is described from the lowest Maastrichtian of Hokkaido, Japan. Its shell is ornamented with very weak, broadly rounded ribs and its suture line is characterized by a deeply incised, trifid dorsal lobe and three bifid lateral saddles with minor indentations. This occurrence suggests that Phylloptychoceras evolved in the North Pacific during late Campanian or early Maastrichtian time and then achieved worldwide distribution during late Maastrichtian time. © by the Palaeontological Society of Japan.


Konishi T.,Royal Tyrrell Museum of Palaeontology | Konishi T.,University of Cincinnati | Caldwell M.W.,University of Alberta | Nishimura T.,Hobetsu Museum | And 2 more authors.
Journal of Systematic Palaeontology | Year: 2015

A specimen of a halisaurine mosasaur is reported from Japan for the first time, closing the pre-existing biogeographical gap between the Middle East and the eastern Pacific. Phosphorosaurus ponpetelegans sp. nov., from the lowermost Maastrichtian of Hokkaido, has been assigned to the genus Phosphorosaurus for sharing the following suite of major cranial characters with P. ortliebi, the type species from Belgium: apex of posterodorsal triangular plateau on frontal reaching level of interorbital constriction; frontal lateral border forming a step-like junction between interorbital and preorbital segments of frontal; preorbital segment of frontal sloping anteroventrally; and stapedial meatus parallel-sided in latero-medial view. Potential autapomorphies that distinguish P. ponpetelegans from other members of Halisaurinae include: postorbitofrontal jugal process elongate and stalk-like, projecting laterally; this process distally bearing a ventrally facing depression for jugal articulation; and lateral surangular–articular suture angular rather than round. The long and laterally projecting jugal processes, when combined with a depressed as well as narrow snout, provide compelling evidence for well-developed binocular vision for the new mosasaur, with an estimated binocular field of view (BFoV) of 35°. This value is unusually high for non-ophidian squamates that typically exhibit a BFoV of 10—20°, and is higher than those of other measured mosasaur taxa by at least 5°. Among colubrid snakes, nocturnal species exhibit greater BFoV than diurnal ones in both arboreal and terrestrial taxa. Known also from the Maastrichtian of Hokkaido are fossils of lantern fish (myctophids) and 10-armed cephalopods (coleoids), both of which are typically bioluminescent today. It is hence proposed that the exceptionally large, forward-facing eyes of P. ponpetelegans may well have been a special adaptation for a nocturnal lifestyle, where they hunted small, bioluminescent prey at night while avoiding direct competition with larger, more piscine mosasaurine taxa such as Mosasaurus hobetsuensis that co-existed with P. ponpetelegans. http://zoobank.org/urn:lsid:zoobank.org:pub:3EF73BE7-B3FE-4441-BA5E-29C5D5FCCBC9 © The Trustees of the Natural History Museum, London 2015. All Rights Reserved.


Nishimura T.,Hobetsu Museum | Maeda H.,Kyoto University | Tanaka G.,Gunma Museum of Natural History | Ohno T.,Kyoto University
Paleontological Research | Year: 2010

Intra- and interspecific variation and ontogenetic changes in various shell characters of the Late Cretaceous desmoceratine ammonoid "Damesites" are described, and their taxonomic implications are discussed based on specimens from the Cretaceous Yezo Group in Hokkaido and Sakhalin. Our study reveals that many "diagnostic" features (e. g., appearance of longitudinal striations, height of ribbing, regularity of ribbing as well as constriction curvature) and early internal shell structures, are in fact inappropriate as diagnostic features of "Damesites" morphotypes. In contrast, ontogenetic changes in shell ornament, curvature of growth lines and whorl expansion ratio are herein demonstrated to be key characters for species recognition and reconstructing the phylogenetic relationships of the taxa of the subfamily Desmoceratinae. Based on these results, previously described "Damesites" species from the uppermost Turonian-lower Campanian interval should be reclassified into three groups. "Damesites damesi," "D. damesi intermedius," "D. semicostatus," and "D. laticarinatus" are assigned to the first group. "D. ainuanus" and "Damesites sp." are assigned to the second group. "D. sugata" from the Yezo Group represents the third group. Furthermore, analysis of ontogenetic changes in shell ornament, curvature of growth lines, and whorl expansion ratio suggests that the second and third groups together belong to a different evolutionary lineage from the first group. © by the Palaeontological Society of Japan.


Shigeta Y.,National Museum of Nature and Science | Izukura M.,N28 E21 1 3 | Nishimura T.,Hobetsu Museum | Tsutsumi Y.,National Museum of Nature and Science
Paleontological Research | Year: 2016

Twelve species of middle and late Campanian (Late Cretaceous) ammonoids, of which one is a newly described species, are reported from the Chinomigawa Formation of the Yezo Group in the Urakawa area, southern central Hokkaido, northern Japan. Furthermore, two ammonoid biozones, the Metaplacenticeras subtilistriatum and Baculites subanceps in ascending order, are recognized. Zircon radiometric ages reveal that the ages of tuffs immediately below the B. subanceps Zone are 75.1±0.9 Ma and 76.0±1.3 Ma respectively, which infer an early late Campanian age. Therefore, the Metaplacenticeras subtilistriatum and Baculites subanceps zones correlate with the upper middle Campanian and lower upper Campanian, respectively. The latter zone is probably a correlative of the lower part of the Didymoceras sp. Zone of the Izumi Group in Southwest Japan because of the discovery of the herein newly described species, Didymoceras hidakense Shigeta sp. nov. Since Didymoceras and Baculites subanceps flourished in other regions during late middle Campanian time, their occurrence in the Urakawa area suggests that they extended their geographic distribution from other areas to the Northwest Pacific region in early late Campanian time. © by the Palaeontological Society of Japan.


Shigeta Y.,National Museum of Nature and Science | Nishimura T.,Hobetsu Museum
Paleontological Research | Year: 2014

Anagaudryceras compressum sp. nov., the most slender of this genus, is newly described from the Nostoceras hetonaiense Zone of earliest Maastrichtian age (Late Cretaceous), in the Hobetsu area, Hokkaido, northern Japan. Its shell is fairly small (< 80 mm in diameter) and compressed with a highly arched venter. The last whorl is ornamented with low, broad, gently flexed band-like ribs. Its ornamentation is very similar to A. matsumotoi, thus suggesting a close phylogenetic relationship with this taxon, which is probably its descendant. © 2014 by the Palaeontological Society of Japan.


Shigeta Y.,National Museum of Nature and Science | Nishimura T.,Hobetsu Museum | Nifuku K.,INPEX Corporation
Paleontological Research | Year: 2014

Nine ammonoid species are reported from the Maastrichtian Senpohshi Formation exposed along the western coast of Akkeshi Bay, eastern Hokkaido, and their respective chronologic assignments are discussed on the basis of a previous magnetostratigraphic study. Pachydiscus flexuosus occurs in the lower and middle parts of the formation (= polarity chron C31n, i.e., middle to upper middle Maastrichtian). Gaudryceras makarovense, Anagaudryceras matsumotoi and Diplomoceras cf. notabile and P. flexuosus as well occur in the lower part (middle middle Maastrichtian). The uppermost part of the formation (= probably the lower part of polarity chron C30n, i.e., lower upper Maastrichtian) is fossiliferous and yields a diverse ammonoid assemblage including Neophylloceras sp., Pseudophyllites sp., Zelandites varuna, A. matsumotoi, Gaudryceras cf. seymouriense, Gaudryceras sp., and D. cf. notabile. Integration of bio- and magnetostratigraphy in the Senpohshi Formation makes it possible to determine precise and detailed chronologic assignment of strata containing similar faunas in the Northwest Pacific realm.


News Article | December 9, 2015
Site: www.rdmag.com

During the Late Cretaceous Period, a 10-ft long beast waited, shrouded in ocean darkness. This nocturnal hunter waited for glowing squid and fish to cross its path before lashing out. While the hunting technique is speculation, the conjecture comes via a new species of mosasaur discovered in a small creek in Japan. “The forward facing eyes on (Phosphorosaurus ponpetelegans) provide depth perception to vision, and it’s common in birds of prey and other predatory mammals that dwell among us today,” said Tayuka Konishi, an assistant professor of biological sciences at the Univ. of Cincinnati. “But we knew already that most mosasaurs were pursuit predators based on what we know they preyed upon—swimming animals. Paradoxically, these small mosasaurs like Phosphorosaurus were not as adept swimmers as their larger contemporaries because their flippers and tailfins weren’t as well developed.” The new fossil species was discovered back in 2009. Found in the northern Japanese town of Mukawa, it was encapsulated in a rock matrix. Over the course of two years, researchers from the Hobetsu Museum bathed the calcareous nodule in an acid wash that eventually freed the bones from the matrix. The fossil was dated to 72 million years ago. “It’s so unusually well-preserved that, upon separating jumbled skull bones from one another, we were able to build a perfect skull with the exception of the anterior third of the snout,” said Konishi. “This is not a virtual reality reconstruction using computer software. It’s a physical reconstruction that came back to life to show astounding detail and beautiful, undistorted condition.” Konishi’s theory regarding the mosasaurs hunting style comes from the skull’s large eye sockets and previous fossilized evidence. Both lantern fish and squid-like animals from the Late Cretaceous period have been found in northern Japan. Unlike their larger cousins, which could grow to 40-ft in length, this smaller mosasaur species’ larger eye sockets suggest the use of binocular vision. According to the Univ. of Cincinnati, binocular vision allows nocturnal hunters to double the amount of photoreceptors used to detect light. “If this new mosasaur was a sit-and-wait hunter in the darkness of the sea and able to detect the light of these other animals, that would have been the perfect niche to coexist with the more established mosasaurs,’ said Konishi. The new research was published in the Journal of Systematic Palaeontology.

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