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Vol.23 No.3
Masanori Okanishi, Yoshiaki Ishida, Shota Mitsui, 2019: Fossil Gorgonocephalid Basket Stars (Echinodermata: Ophiuroidea: Euryalida) from the Middle Pleistocene of Japan; the First Record from the Indo-Pacific Region. Paleontological Research, Vol.23 No.3, 179-185. 10.2517/2018PR017. https://doi.org/10.2517/2018PR017
Disarticulated fossil euryalid ophiuroid vertebrae from the Middle Pleistocene Miyata Formation, Miura, Kanagawa Prefecture, eastern Japan, are described. The vertebrae are assigned to the family Gorgonocephalidae on the basis of arm branching and the presence of an open oral groove along the entire arm. This is the first record of fossil euryalids from the Indo-Pacific region.
Megumi Nishino, Toshihiro Yamada, 2019: Limnobiophyllum expansum (Lemnoideae, Araceae) from the Early Miocene Hiramaki Formation in the Kani Basin, Gifu Prefecture, Central Japan. Paleontological Research, Vol.23 No.3, 186-191. 10.2517/2018PR018. https://doi.org/10.2517/2018PR018
Limnobiophyllum expansum (Lemnoideae, Araceae) was newly found in the lower Miocene (18.4–17.0 Ma) Hiramaki Formation of the Mizunami Group in the Kani Basin, Gifu Prefecture, central Japan. This genus was distributed widely in the Northern Hemisphere from the Late Cretaceous to the Paleocene, but a Miocene descendant (L. expansum) was reported only from Europe, in the Bohemian Basin, Czech Republic (early Miocene), Paldau, Austria (late Miocene), Schrotzburg, Switzerland (late Miocene) and Sośnica, Poland (late Miocene). Our finding is the first record of a Miocene Limnobiophyllum from an area other than Europe. The aquatic flora of Japan during the early Miocene is poorly documented, but this finding suggests a link between the aquatic floras of Europe and Asia.
Jun-Ichi Tazawa, Hiroshi Kurita, 2019: Two Early Carboniferous Brachiopods, Levitusia humerosa (Sowerby, 1822) and Grandispirifer mylkensis Yang, 1959, from the Arisu Formation of Okuhinotsuchi, South Kitakami Belt, Japan. Paleontological Research, Vol.23 No.3, 192-198. 10.2517/2018PR019. https://doi.org/10.2517/2018PR019
Two early Carboniferous brachiopod species, Levitusia humerosa (Sowerby) and Grandispirifer mylkensis Yang, are described from Japan for the first time. These species, from the middle part of the Arisu Formation in the Okuhinotsuchi area, South Kitakami Belt, indicate an early Visean age. Therefore, the middle part of the Arisu Formation is correlated with the lower Visean. In terms of palaeobiogeography, occurrence of the two species suggests that South Kitakami was probably the eastern extension of the North China Province, and located near and to the east of North China (Sino-Korea) during the early Visean.
Yoshihiro Tanaka, Masaaki Ohara, Toshiyuki Kimura, 2019: A Large Fossil Baleen Whale from the Shikiya Formation (Early Middle Miocene) of Wakayama, Japan. Paleontological Research, Vol.23 No.3, 199-207. 10.2517/2018PR020. https://doi.org/10.2517/2018PR020
A new large Chaeomysticeti indet., WMNH-Ge-1140240005 from the Shikiya Formation of Kumano Group (early middle Miocene; about 16 to 15 Ma) of Wakayama, Japan is described here. It preserves a large rostrum (about 50 cm width at the base of the rostrum), which has gently tapered lateral margins of the rostrum, narrow mesorostral groove at the level of the narial fossa, and wide premaxillae and maxillae. There are no diagnostic features pertaining to the specimen at the family level, but it is comparable to “cetotheres” sensu lato such as Pelocetus calvertensis and Diorocetus hiatus by having wide premaxillae that occupy 1/3 width of the rostrum anterior to the narial fossa in dorsal view, which implies that WMNH-Ge-1140240005 is a possible member of “cetotheres” sensu lato. Its size is possibly between the two large species Pelocetus calvertensis and Diorocetus hiatus of the early middle Miocene, and larger than the reported middle Miocene mysticete specimens from Japan (“Diorocetus” chichibuensis, “Diorocetus” shobarensis, Parietobalaena sp. (SMNH-VeF-62)). The rostral width of WMNH-Ge-1140240005 suggests that this animal was medium-sized compare to extant species, but the largest in the class of baleen whales of its time.
Kazutaka Amano, Yusuke Miyajima, Kenyu Nakagawa, Masui Hamuro, Toshikazu Hamuro, 2019: Chemosymbiotic Bivalves from the Lower Miocene Kurosedani Formation in Toyama Prefecture, Central Honshu, Japan. Paleontological Research, Vol.23 No.3, 208-219. 10.2517/2018PR022. https://doi.org/10.2517/2018PR022
Many molluscan fossils have been found from the turbidite deposits of the lower Miocene Kurosedani Formation at Kakuma in Toyama City. They include six chemosymbiotic bivalves, namely Solemyidae gen. et sp. indet., Nucinella sp., Luinoma cf. acutilineatum (Conrad), Conchocele yatsuoensis sp. nov., Pliocardia kawadai (Aoki) and Adulomya chitanii Kanehara. This is the oldest record of chemosymbiotic species in the Japan Sea region. Nucinella has been unknown from the Cenozoic deposits in the Japan Sea borderland and from the Recent Japan Sea. Moreover, the vesicomyids P. kawadai and A. chitanii are shared with those from the lower Miocene Honya Formation in Fukushima Prefecture and from the middle Miocene Nupinai Formation in eastern Hokkaido. This supports our hypothesis that the invasion of chemosymbiotic species from the Pacific side to the Japan Sea took place soon after the formation of a deep-sea basin in the Japan Sea.
Evgeny V. Popov, Dominique Delsate, Roland Felten, 2019: A New Callorhinchid Genus (Holocephali, Chimaeroidei) from the Early Bajocian of Ottange-Rumelange, on the Luxembourg-French Border. Paleontological Research, Vol.23 No.3, 220-230. 10.2517/2018PR021. https://doi.org/10.2517/2018PR021
An incomplete chimaeroid (Holocephali, Chimaeroidei) mandibular dental plate from the early Bajocian (Humphriesianum Zone) of Ottange-Rumelange, on the Luxembourg-French border, is described as a new genus and species of callorhinchid fish Ottangodus lotharingiae gen. et sp. nov. Comparison of the described plate with other Jurassic chimaeriform fish (both myricanthid and chimaeroid) mandibular plates shows relationships with callorhinchids and in turn close relationships with the genus Pachymylus Woodward, known from the Callovian of England. The plate of the new genus shows a set of primitive characters for chimaeroids (very high descending lamina, low oral part of the plate, large centrally placed median tritor occupying most of the oral part of the plate and an absence of mesio-labial system of the tritors) and could thus belong to a basal Chimaeroidei taxon. This is the first record of the Chimaeroidei from the Jurassic of Lorraine and the fourth chimaeriform genus known from the Mesozoic of the region.