Origin of Cyclic Sedimentation in Middle Miocene Siliceous Rocks of Northern Japan: ABSTRACT

AAPG Bulletin ◽  
1990 ◽  
Vol 74 ◽  
Author(s):  
Tada Ryuji, Azuma Iijima
Keyword(s):  
Middle Miocene ◽  
Cyclic Sedimentation ◽  
Siliceous Rocks ◽  
Northern Japan

Reinterpretation of the Miocene Sea-Snake Egg Moniopterus Japonicus as a Boring of Rock-Boring Bivalve Lithophaga (Mytilidae: Mollusca)

2010 ◽  
Vol 84 (5) ◽  
pp. 848-857 ◽  
Author(s):  
Takuma Haga ◽  
Yukito Kurihara ◽  
Tomoki Kase
Keyword(s):  
Middle Miocene ◽  
Scanning Electronic Microscopy ◽  
Electronic Microscopy ◽  
Sea Snake ◽  
Senior Synonym ◽  
Coleopteran Insect ◽  
Pointed End ◽  
Oval Shape ◽  
Northern Japan

The enigmatic fossil Moniopterus japonicus Hatai et al., 1974 from the early Middle Miocene Moniwa Formation of northern Japan has been described as the only known example of fossil sea-snake eggs and also as fossilized pupal chambers of a coleopteran insect. A reexamination of the holotype provides no evidence in support of these previous interpretations. Scanning electronic microscopy and computed tomography observations on the holotype reveal that the calcareous lining, previously interpreted as eggshell, is instead composed of irregular spherulitic prisms, thin in the middle and becoming thicker toward both ends. In addition to the elongate oval shape and the presence of an opening at the more pointed end, these observations strongly suggest that M. japonicus is a boring of the mytilid boring bivalve Lithophaga isolated from the host rock. This reinterpretation is further supported by the occurrence of similar isolated and in situ borings with Lithophaga shells within the type and a nearby locality. Regarding this fossil as an ichnofossil makes the generic name Moniopterus a junior synonym of Gastrochaenolites Leymerie, 1842 and the species name japonicus is a senior synonym of Gastrochaenolites torpedo Kelly and Bromley, 1984. G. torpedo should thus be replaced with Gastrochaenolites japonicus (Hatai et al., 1974).

scholarly journals A new Miocene pinniped Allodesmus (Mammalia: Carnivora) from Hokkaido, northern Japan

2018 ◽  
Vol 5 (5) ◽  
pp. 172440 ◽  
Author(s):  
Wataru Tonomori ◽  
Hiroshi Sawamura ◽  
Tamaki Sato ◽  
Naoki Kohno
Keyword(s):  
Phylogenetic Analysis ◽  
New Species ◽  
North Pacific ◽  
Western North Pacific ◽  
Middle Miocene ◽  
Incisive Foramen ◽  
Northern Japan

A nearly complete pinniped skeleton from the middle Miocene Okoppezawa Formation ( ca 16.3–13.9 Ma), Hokkaido, northern Japan, is described as the holotype of Allodesmus uraiporensis sp. nov. The new species is distinguishable from other species of the genus by having the palatine fissure (incisive foramen) that is located anterior to the canine, an anteriorly located supraorbital process of the frontal, and by having the calcaneum with a developed peroneal tubercle. Our phylogenetic analysis suggests that the subfamily Allodesminae are represented by two genera, Atopotarus and Allodesmus , and the latter genus is represented by at least six species; Al . kernensis , Al . sinanoensis , Al . naorai , Al . packardi, Al. demerei and Al. uraiporensis sp. nov. Allodesmus uraiporensis sp. nov. is one of the oldest and the northernmost record of the genus in the western North Pacific, and it suggests that the diversification of the genus in the western North Pacific was synchronous to the time of their diversification in the eastern North Pacific.

scholarly journals A new kentriodontid (Cetacea: Odontoceti) from the early to middle Miocene of the western North Pacific and a revision of kentriodontid phylogeny

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10945
Author(s):  
Zixuan Guo ◽  
Naoki Kohno
Keyword(s):  
New Species ◽  
Middle Miocene ◽  
Sister Group ◽  
Posterior View ◽  
Anterior Dorsal ◽  
Initial Evolution ◽  
Narrow Width ◽  
Iwate Prefecture ◽  
A New Species ◽  
Northern Japan

A new species of an extinct dolphin belonging to the kentriodontids, i.e., Kentriodon sugawarai sp. nov., is described from the upper lower to lowest middle Miocene Kadonosawa Formation in Ninohe City, Iwate Prefecture, northern Japan. The holotype of Kentriodon sugawarai sp. nov., consists of a partial skull with ear bones, mandibular fragments, and some postcranial bones. This new species shares five unique characters with other species of Kentriodon. In addition, the new species differs from other species of the genus in displaying a narrow width of the squamosal lateral to the exoccipital in posterior view, the dorsolateral edge of the opening of the ventral infraorbital foramen that is formed by the maxilla and the lacrimal or the jugal, and at least three anterior dorsal infraorbital foramina. Our phylogenetic analysis based on 393 characters for 103 Odontoceti taxa yielded a consensus tree showing all previously identified kentriodontids as a monophyletic group that comprises the sister group of the crown Dephinoidea, which in turn include Delphinidae, Phocoenidae and Monodontidae. Our analysis also indicates that the distinct innovation of the acoustic apparatus (i.e., 13 out of 29 derived characters are from tympanoperiotic) would have occurred in the ancestral lineage of the Delphinoidea (sensu lato) including the monophyletic Kentriodontidae during their initial evolution and diversification.

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