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Arnioceras — Arnioceras
Arnioceras — Daderot, Wikimedia Commons, CC0

Ammonoid

Arnioceras

Sinemurian ammonite

Arnioceras is the small, sharply ribbed, keeled Sinemurian ammonite found in clusters on Lyme Regis and Charmouth limestone, often as blocks packed with dozens of individuals. Multi-ammonite Arnioceras blocks are beach finds under the Jurassic Coast code and modest in price. It is easily confused with juvenile Asteroceras and Promicroceras.

PhylumMollusca
ClassCephalopoda
OrderAmmonitida
FamilyArietitidae
GroupAmmonoid
Rank (PBDB)genus· Paleobiology Database
AuthorHyatt 1867· Paleobiology Database
Classification (PBDB)Mollusca › Cephalopoda › Ammonitida › Arietitidae· Paleobiology Database
Range (PBDB)201–175 Ma· Paleobiology Database
PBDB occurrences368· Paleobiology Database

Photographs

Arnioceras — Arnioceras bodleyi (J. Buckman) (NHMUK PI C 2220)
Arnioceras bodleyi (J. Buckman) (NHMUK PI C 2220) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0

Age

Formations

Elsewhere

Cite this article

Stratum Study. "Arnioceras" (Taxon). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/taxa/arnioceras. Accessed 2026-09-20.

BibTeX · CSL-JSON

@misc{stratum-arnioceras,
  title        = {Arnioceras},
  author       = {{Stratum Study}},
  howpublished = {\url{https://stratum.black/study/taxa/arnioceras}},
  year         = {2026},
  note         = {Taxon article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum, pbdb, wikidata, commons, nhm. Accessed 2026-09-20.}
}

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