Article
Geology
Shiori Kanno, Sayaka Tokumaru, Shuhei Nakagaki, Yasuhisa Nakajima, Akihiro Misaki, Yoshinori Hikida, Tamaki Sato
Summary: This study describes 51 fossil shark teeth, including Hexanchiformes, Echinorhiniformes, Squaliformes, and Lamniformes, from two localities in Hokkaido, Japan. The presence of Protosqualus in the northwestern Pacific suggests the early Campanian onset of deep-water adaptation for Squaliformes in this region. Different sedimentary settings at the two localities may have influenced the taxonomic compositions. The co-existence of Hexanchiformes and Lamniformes in contemporaneous Japanese fauna and southern high latitudes indicates the paleogeographic effects on the global distribution of Upper Cretaceous neoselachian taxa.
CRETACEOUS RESEARCH
(2022)
Article
Paleontology
Daisuke Aiba
Summary: This study investigates the mature modifications, ontogeny, and dimorphism of the small-sized tetragonitid ammonoid Tetragonites minimus in the Upper Cretaceous of Hokkaido, Japan. It found significant size differences between adults and suggests that T. minimus may have changed habitats during its life cycle.
ACTA PALAEONTOLOGICA POLONICA
(2022)
Article
Geochemistry & Geophysics
Lydian M. Boschman, Douwe J. J. Hinsbergen, Wim Spakman
Summary: The study reconstructs the plate tectonic evolution of the pre-Cretaceous intra-oceanic subduction zone and reveals the disappearance and subsequent extension of the Oku-Niikappu island arc during a change in spreading direction, indicating the reasons behind plate subduction and divergence.
Article
Geology
Kazushige Tanabe, Akihiro Misaki
Summary: Taxonomic study of two lower jaws and one upper jaw of coleoid cephalopods recovered from Upper Cretaceous strata in Hokkaido, Japan suggests that the two lower jaws are conspecific with Longibelus matsumotoi and the upper jaw is likely from the Oegopsida order. Similarity between the lower jaws of L. matsumotoi (?) and the modern ram's horn squid Spirula spirula supports the evolutionary scenario from Longibelus to Decapodiformes. The large oegopsid jaws found in this study provide a reliable fossil record for inferring the evolutionary history of this order.
CRETACEOUS RESEARCH
(2023)
Article
Geology
Homare Sakaki, Daniela E. Winkler, Tai Kubo, Ren Hirayama, Hikaru Uno, Shinya Miyata, Hideki Endo, Kazuhisa Sasaki, Toshio Takisawa, Mugino O. Kubo
Summary: Sauropod teeth from the Tamagawa Formation in northeastern Japan were studied to infer the diet of a titanosauriform sauropod. The research suggests that the sauropod primarily fed on soft plant materials and existed during the late Turonian in East Asia.
CRETACEOUS RESEARCH
(2022)
Article
Geochemistry & Geophysics
Yusuke Miyajima, Michal Jakubowicz, Jolanta Dopieralska, Akihiro Kano, Robert G. Jenkins, Zdzislaw Belka, Takafumi Hirata
Summary: This study investigates the hydrogeological regime and structural evolution of the Cretaceous subduction zone in Hokkaido, Japan, by analyzing the timing and migration pathways of fluids emitted at ancient methane seeps. Results show that two fluid discharge events occurred during the accretionary stages, originating from the forearc basin rather than the underplating materials. The seeping fluids experienced interactions with the mafic rocks of the lower Sorachi ophiolite and siliciclastic sediments of the Yezo Group.
Article
Geology
Julien Legrand, Toshihiro Yamada, Harufumi Nishida
Summary: A new taxon, Yezopollis mikasaensis gen. et sp. nov., is described based on Normapolles-type angiosperm pollen grains obtained from the Mikasa Formation in Mikasa City, Hokkaido, Japan. This new taxon adds a new record to the Normapolles complex and represents the earliest Normapolles-type representative found outside of the province. The co-occurrence of Y. mikasaensis and E. cuneifolia suggests that some early eudicots exhibited intermixed features of extant basal eudicot families if they were shed by the same plant species.
CRETACEOUS RESEARCH
(2022)
Article
Geosciences, Multidisciplinary
Shunta Sakai, Naoto Hirano, Yildirim Dilek, Shiki Machida, Kazutaka Yasukawa, Yasuhiro Kato
Summary: The Tokoro Belt in NE Hokkaido is part of a Late Cretaceous accretionary complex that is distinct from others around the Pacific Rim due to the abundant presence of basalts and volcaniclastic rocks. The Nikoro Group, characterized by widespread occurrence of volcanic rocks, is divided into western, eastern and southern sections based on internal structure, geochemical affinities and metamorphic grades. The OIB-type volcanic rocks dominate in the western and southern sections, while MORB- and OIA-type rocks are found in the eastern section.
GEOLOGICAL MAGAZINE
(2021)
Article
Zoology
Hirotaka Tanaka, Daisuke Sasaki, Satoshi Kamitani
Summary: This study describes a new species of soft scale insect, Luzulaspis kinakikir Tanaka sp. nov., collected from Carex miyabei on Hokkaido Island, Japan, based on adult female morphology. The new species, belonging to the Scotica group of Luzulaspis, can be distinguished from other species by characteristics such as the distribution of multilocular pores, morphology of tubular ducts, and absence of dorsal tubular ducts on the head.
Article
Plant Sciences
Harufumi Nishida, Ruth A. Stockey, Yusuke Takebe, Julien Legrand, Toshihiro Yamada
Summary: This study describes a new genus of a probable stem polypodioid leptosporangiate fern based on a permineralized fertile pinnule from the Late Cretaceous Yezo Group in Hokkaido, Japan. The study provides insights into the diversity of ferns during this period, challenging previous assumptions.
INTERNATIONAL JOURNAL OF PLANT SCIENCES
(2022)
Article
Paleontology
Eduardo Villalobos-Segura, Charlie J. Underwood, David J. Ward
Summary: A new fossil batoid species, Ptychotrygon rostrispatula, was discovered in Morocco. The skeletal remains of this species provide new insights into its phylogenetic relations and confirm its taxonomic status within the Sclerorhynchoidei subfamily. The study also revealed similarities in morphology with other sclerorhynchoids, suggesting a relatively large body size for this species.
PAPERS IN PALAEONTOLOGY
(2021)
Article
Paleontology
Yusuke Muramiya, Yasunari Shigeta
Summary: A new heteromorph ammonoid Sormaites teshioensis gen. et sp. nov. from the upper Turonian in northern Japan was described, showing similarities in coiling and ornamentation to other taxa in the Northwest Pacific, suggesting a possible evolutionary relationship.
PALEONTOLOGICAL RESEARCH
(2021)
Article
Zoology
Tomoyuki Komai, Koji Matsuzaki
Summary: This paper describes three new species of deep-water caridean shrimps collected in Nemuro Strait, southwestern part of the Sea of Okhotsk, using commercial baited traps and gill nets. Morphological comparison and genetic analyses were used to determine the specific identities of these newly recognized taxa. Additionally, an aberrant male specimen of L. fujimotoi was reported and its identity was confirmed through genetic analyses.
Article
Plant Sciences
Brian A. Atkinson, Dori L. Contreras, Ruth A. Stockey, Gar W. Rothwell
Summary: This study characterizes two new extinct genera of conifers, expanding the taxonomic and morphological diversity within the Cunninghamioideae subfamily. The research shows that Cunninghamioideae peaked in diversity during the Cretaceous, with most extinct genera disappearing by the end of the Campanian period.
Article
Paleontology
Terry Markham Puckett, Gene Hunt
Summary: This contribution describes new species, genera, and a subfamily of ostracods from marine deposits in the eastern flank of the Mississippi Embayment. These new taxa display rapid evolution and have distinctive features. They are mainly found on the eastern flank of the Mississippi Embayment and the Atlantic Coastal Plain, with no observations on the western flank. The group became extinct at the Cretaceous-Paleogene boundary.
