Stratum.black
Asteroceras — Asteroceras
Asteroceras — Dlloyd, Wikimedia Commons, CC BY SA 3.0

Ammonoid

Asteroceras

Star ammonite

Asteroceras obtusum is the large, keeled Sinemurian ammonite of Charmouth's Black Ven, found in limestone nodules and prepared with the surrounding matrix into handsome pieces up to 25 cm. It is the most sought-after Lyme Regis ammonite for display and prepared examples from the 'obtusum' nodule bed sell for hundreds of pounds. Check for replaced body chambers.

PhylumMollusca
ClassCephalopoda
OrderAmmonitida
FamilyArietitidae
GroupAmmonoid
Rank (PBDB)genus· Paleobiology Database
AuthorHyatt 1867· Paleobiology Database
Classification (PBDB)Mollusca › Cephalopoda › Ammonitida › Asteroceratidae· Paleobiology Database
Range (PBDB)201–175 Ma· Paleobiology Database
PBDB occurrences91· Paleobiology Database
Authority (WoRMS)Lyman, 1879· WoRMS / MolluscaBase
Status (WoRMS)unaccepted· WoRMS / MolluscaBase
Valid name (WoRMS)Astroceras· WoRMS / MolluscaBase
Classification (WoRMS)Animalia › Echinodermata › Ophiuroidea › Euryalida › Euryalidae· WoRMS / MolluscaBase

Photographs

Asteroceras — Asteroceras stellare (Sowerby, 1815) (NHMUK PI C 79644)
Asteroceras stellare (Sowerby, 1815) (NHMUK PI C 79644) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0
Asteroceras — Asteroceras blakei Spath, 1925 (NHMUK PI C 68159)
Asteroceras blakei Spath, 1925 (NHMUK PI C 68159) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0
Asteroceras — Asteroceras stellare (Sowerby, 1815) (NHMUK PI OR 43969 (a))
Asteroceras stellare (Sowerby, 1815) (NHMUK PI OR 43969 (a)) — © 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. "Asteroceras" (Taxon). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/taxa/asteroceras. Accessed 2026-09-20.

BibTeX · CSL-JSON

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

Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.