Select Page

Echinoidea

Back to Echinoderms
Exhibit Home
Back to Meet the Fossils
A scene underwater with various invertebrate animals like sea urchins and fish swimming in the background.
Underwater scene with a "fuzzy" sea star on a rock with sand and vegetation behind it.

Modern Day Echinoids

Echinoids are more commonly known as sea urchins. There are around 900+ identified species today.

In the Museum Collections

View specimen list here.

Total echinoid specimens: 570

Total identified species: 37

Specimens from Arkansas: 493

Identified species from Arkansas: 4

Fossil Record

The earliest echinoid fossils date back to the Ordovician Period (485.4 – 443.8 million years ago).

Two echinoid fossils
Arkansas map indicating Clark Co

Echinoid specimens (UA Museum), Saratoga Chalk Formation (Clark County, AR), Upper Cretaceous (100.5 – 66 million YA). Map on right indicates the county where the specimens were found.

Image Credits:

  • Ducarme, Frédéric. A flat sea urchin (or “sand dollar”) Clypeaster reticulatus seen in Mayotte. Wikimedia Commons. CC BY-SA 4.0.
  • Nhobgood (Nick Hobgood). Tripneustes ventricosus (West Indian Sea Egg-top) and Echiometra viridis (reef Urchin-bottom). Wikimedia Commons. CC BY 3.0. 
  • Oberg, Danielle. Arkansas map.
  • Oberg, Danielle. U of A Museum paleontological specimens.