Ammonoid
Placenticeras meeki
Ammonite
Placenticeras is the large, smooth, discoidal ammonite of the Pierre Shale and Bearpaw Formation, the genus that produces iridescent ammolite in Alberta and the red-green nacreous ammonites of South Dakota. Complete P. meeki with shell are prized; steinkerns with exposed sutures are cheaper and also collectible. Look for repaired body chambers and shell reattached over fill.
| Phylum | Mollusca |
|---|---|
| Class | Cephalopoda |
| Order | Ammonitida |
| Family | Placenticeratidae |
| Group | Ammonoid |
| Size | to 60 cm |
| Rank (PBDB) | genus· Paleobiology Database |
| Author | Meek 1876· Paleobiology Database |
| Classification (PBDB) | Mollusca › Cephalopoda › Ammonitida › Placenticeratidae· Paleobiology Database |
| Range (PBDB) | 106–66 Ma· Paleobiology Database |
| PBDB occurrences | 241· Paleobiology Database |
Restoration and fakes
Large Pierre Shale ammonites are commonly assembled from concretion fragments and gap-filled; shell may be stabilised with resin that mimics nacre.
Photographs
Elsewhere
- GBIF: 4626179
- PBDB: 15403
- Wikidata: Q18388822
- PBDB taxon page
- Wikipedia: Placenticeras meeki
- PBDB search: Placenticeras
Cite this article
Stratum Strata. "Placenticeras meeki" (Taxon). Stratum Strata pack 2026.09, as of 2026-09-21. https://stratum.black/strata/taxa/placenticeras-meeki. Accessed 2026-09-21.
@misc{stratum-placenticeras-meeki,
title = {Placenticeras meeki},
author = {{Stratum Strata}},
howpublished = {\url{https://stratum.black/strata/taxa/placenticeras-meeki}},
year = {2026},
note = {Taxon article, Stratum Strata pack 2026.09, as of 2026-09-21; sources: stratum, pbdb, wikidata, commons, nhm. Accessed 2026-09-21.}
} 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.