Ashizawa Formation

Ashizawa Formation
Stratigraphic range: Coniacian
TypeGeological formation
Unit ofFutaba Group
Sub-unitsAsamigawa Member, Obisagawa Member
UnderliesKasamatsu Formation
OverliesEarly Cretaceous Granite, Permian shale and sandstone
Location
Regionnorthern Honshu
CountryJapan

The Ashizawa Formation is a Coniacian geologic formation in northeastern Honshu, Japan. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus. A jawbone belonging to a therian mammal has also been discovered from this unit.

Fossil content

The following fossils were reported from the formation:

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon

Notes
Uncertain or tentative taxa are in small text
crossed out taxa are discredited.

Dinosaurs

Ornithischians

Ornithischians of the Ashizawa Formation
Genus Species Location Stratigraphic position Material Notes Image
Hadrosauroidea Indet. Indeterminate Fukushima Prefecture, Honshu, Japan Coniacian A hadrosauroid ornithopod
Styracosterna indet. Indeterminate Fukushima Prefecture, Honshu, Japan Coniacian A styracosternan iguanodonian

Theropods

Theropos of the Ashizawa Formation
Genus Species Location Stratigraphic position Material Notes Image
Theropoda indet. Indeterminate Fukushima Perfecture, Honshu, Japan Coniacian Tibia An indeterminate theropod; informally known as "Futabasaurus".

Mammals

Mammals of the Ashizawa Formation
Genus Species Location Stratigraphic position Material Notes Image
Theria indet. Indeterminate Fukushima Perfecure, Honshu, Japan Coniacian An indeteminate therian.

Fish

Fishes of the Ashizawa Formation
Genus Species Location Stratigraphic position Material Notes Image
Squalus S. sp. Fukushima Perfecture, Honshu, Japan Coniacian An spurdog

Mollusks

Bivalves

Bivalves of the Ashizawa Formation
Genus Species Location Stratigraphic position Material Notes Image
Inoceramus I. uwajimensis Fukushima Prefecture, Honshu, Japan Coniacian A inoceramid bivalve

Cephalopods

Cephalopods of the Ashizawa Formation
Genus Species Location Stratigraphic position Material Notes Image
Anagaudryceras A. limatum Fukushima Prefecture, Honshu, Japan Coniacian A gaudryceratid lytoceratine
Eubostrychoceras E. indopacificum Fukushima Prefecture, Honshu, Japan Coniacian A nostoceratid turrilitoid
Forresteria F. alluaudi Fukushima Prefecture, Honshu, Japan Coniacian A barroisiceratine collignoniceratid
Gaudryceras G. denseplicatum Fukushima Prefecture, Honshu, Japan Coniacian A gaudryceratid lytoceratine
Pseudoxybeloceras P. sp. Fukushima Prefecture, Honshu, Japan Coniacian A diplomoceratid ammonite
Tongoboryceras T. kawashitai Fukushima Prefecture, Honshu, Japan Coniacian A pachydiscid desmoceratoid
Yabeiceras Y. orientale Fukushima Prefecture, Honshu, Japan Coniacian A barroisiceratine collignoniceratid
Yezoceras Y. elegans Fukushima Prefecture, Honshu, Japan Coniacian A nostoceratid turrilitoid
Y. miotuberculatum
Yezoites Y. pseudoaequalis Fukushima Prefecture, Honshu, Japan Coniacian A otoscaphitine scaphitid

See also

Footnotes

  1. ↑ Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
  2. ↑ Kusuhashi, N., Suzuki, T., Terui, K., Sato, A., and Amiot, R. (2016) A Late Cretaceous mammalian dentary from the Ashizawa Formation (Futaba Group), Fukushima, northeastern Japan. Island Arc, 25: 403–409. doi: 10.1111/iar.12133.
  3. ↑ Kondo, M.; Tanaka, K.; Utagawa, F.; Yoshida, J.; Zelenitsky, D. K. (2026). "An iguanodontian sternal plate from the Upper Cretaceous Ashizawa Formation (Futaba Group) of Fukushima Prefecture, Japan". Paleontological Research. 30: 122–134. doi:10.2517/prpsj.250042.
  4. ↑ Lambert, David; the Diagram Group (1990). The Dinosaur Data Book. New York: Avon Books. pp. 63–66, 250. ISBN 978-0-380-75896-8.

References