The Akaiwa Formation ( ja, 赤岩層, translit=Akaiwa-sō) is an

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

(

Hauterivian The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.9 ± 2 Ma and 129.4 ± 1.5 Ma (million years ago). The Hauterivian is preceded by the Va ...

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is preceded ...

) geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

in central

Honshu , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island separ ...

, Japan.Akaiwa Formation
in the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pale ...

Indeterminate

ornithischia Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek s ...

n fossils are known from the formation. Fossil

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world ...

tracks have been reported from the formation.Weishampel et al., 2004, pp.517-607 As well as the turtle '' Kappachelys''Hirayama et al., 2013

Fossil content

The following fossils have been reported from the formation: * Osteichthyes indet. - 'fish scales' ;Reptiles *

Turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...

s ** '' Kappachelys okurai'' * Crocodylomorpha indet. - isolated teeth of small crocodilesMatsukawa & Obata, 1994 * ?Euornithopoda indet. * Neochoristodera indet. - a nearly complete right premaxillaMatsumoto et al., 2014 * Ornithopoda indet. - isolated teeth of small ornithopods * ?Theropoda indet. ;Ichnofossils * Ornithischia indet. - tracksAzuma & Tomida, 1995

References

Bibliography

* * * * * {{cite LSA , last=Matsukawa , first=M. , first2=I. , last2=Obata , year=1994 , title=Dinosaurs and sedimentary environments in the Japanese Cretaceous: a contribution to dinosaur facies in Asia based on molluscan palaeontology and stratigraphy , journal=

Cretaceous Research ''Cretaceous Research'' is a bimonthly peer-reviewed scientific journal published by Elsevier. The journal focuses on topics dealing with the Cretaceous period and the Cretaceous–Paleogene boundary. Abstracting and indexing The journal is abst ...

, volume=15 , pages=101–125 Geologic formations of Japan Lower Cretaceous Series of Asia Barremian Stage Hauterivian Stage Sandstone formations Conglomerate formations Fluvial deposits Paludal deposits Ichnofossiliferous formations Paleontology in Japan

Fossil content

See also

References

Bibliography