Crinoid
Uintacrinus socialis
Free-floating crinoid
Uintacrinus socialis is the stemless, free-floating crinoid of the Niobrara Chalk, found as slabs where dozens of globular calices and long arms tangle together. Uintacrinus plates are a Kansas speciality and sell from a few hundred dollars for small slabs to five figures for large ones. The chalk is soft, so slabs are consolidated and often backed.
| Phylum | Echinodermata |
|---|---|
| Class | Crinoidea |
| Order | Uintacrinida |
| Family | Uintacrinidae |
| Group | Crinoid |
| Rank (PBDB) | genus· Paleobiology Database |
| Author | Grinnell 1876· Paleobiology Database |
| Classification (PBDB) | Echinodermata › Crinoidea › Comatulida › Uintacrinidae· Paleobiology Database |
| Range (PBDB) | 89.8–83.6 Ma· Paleobiology Database |
| PBDB occurrences | 4· Paleobiology Database |
Photographs
Elsewhere
Cite this article
Stratum Strata. "Uintacrinus socialis" (Taxon). Stratum Strata pack 2026.09, as of 2026-09-21. https://stratum.black/strata/taxa/uintacrinus-socialis. Accessed 2026-09-21.
@misc{stratum-uintacrinus-socialis,
title = {Uintacrinus socialis},
author = {{Stratum Strata}},
howpublished = {\url{https://stratum.black/strata/taxa/uintacrinus-socialis}},
year = {2026},
note = {Taxon article, Stratum Strata pack 2026.09, as of 2026-09-21; sources: stratum, pbdb, 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.