Stratum.black
Hemiaster — Hemiaster (NHMUK PI EE 6077 a)
Hemiaster (NHMUK PI EE 6077 a) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0

Echinoid

Hemiaster

Heart urchin

Hemiaster is the small heart-shaped irregular urchin common in the Cretaceous of Texas (Grayson Marl, Duck Creek), Morocco and Europe, found by the dozen in marl exposures around Fort Worth and Denton. Texas Hemiaster are cheap and legal from private land and road cuts with permission; Moroccan examples are often polished. The petal-shaped ambulacra are the diagnostic feature.

PhylumEchinodermata
ClassEchinoidea
OrderSpatangoida
FamilyHemiasteridae
GroupEchinoid
Rank (PBDB)genus· Paleobiology Database
AuthorAgassiz and Desor 1847· Paleobiology Database
Common name (PBDB)heart urchin· Paleobiology Database
Classification (PBDB)Echinodermata › Echinoidea › Spatangoida › Hemiasteridae· Paleobiology Database
Range (PBDB)120–3.6 Ma· Paleobiology Database
PBDB occurrences376· Paleobiology Database

Photographs

Hemiaster — Hemiaster (NHMUK PI EE 6077 c)
Hemiaster (NHMUK PI EE 6077 c) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0
Hemiaster — Hemiaster (NHMUK PI EE 6077 b)
Hemiaster (NHMUK PI EE 6077 b) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0
Hemiaster — Hemiaster (NHMUK PI EE 4850 a)
Hemiaster (NHMUK PI EE 4850 a) — © The Trustees of the Natural History Museum, London, Natural History Museum (London) Data Portal, CC BY 4.0

Age

Elsewhere

Cite this article

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

BibTeX · CSL-JSON

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