Where to find echinoids

Frequently asked questions

How do I identify an echinoid fossil?

Echinoid tests (shells) typically show five-fold radial symmetry — five ambulacral zones (where tube feet emerged) alternate with five interambulacral zones around the test. Regular echinoids are circular or domed when viewed from above, with the mouth at the centre of the flat base and the anus (periproct) at the top. Irregular echinoids, including heart urchins and sand dollars, are bilateral rather than radially symmetric — elongated in plan view, with the mouth shifted toward one end and a distinct petal-shaped pattern of ambulacral pores on the upper surface. Heart urchins of the genus Micraster from the Cretaceous chalk are among the most common complete fossils found in southern England and Denmark. Echinoid spines are also common isolated finds in Mesozoic and Cenozoic marine limestones, though they are rarely still attached to the test.

Where can I find echinoid fossils?

Cretaceous chalk deposits in southern England and Denmark are the premier echinoid collecting areas. Stevns Klint in Denmark (UNESCO World Heritage Site) and Flamborough Head in Yorkshire both produce Micraster and Echinocorys from the Cretaceous chalk. In southern England, ploughed chalk fields in Hampshire, Wiltshire, and Hertfordshire regularly bring echinoids to the surface, and beaches at Beachy Head and the Seven Sisters in East Sussex produce specimens eroded from the cliffs. Morocco's Cretaceous phosphate and limestone deposits near Khouribga produce echinoids alongside shark teeth. Mineral Wells Fossil Park in Texas and Caesar Creek State Park in Ohio both yield Carboniferous echinoid fragments, though complete tests from this period are rare.

Are echinoids still alive today?

Yes — sea urchins are among the most familiar living marine invertebrates. Approximately 950 living echinoid species exist, ranging from regular sea urchins and irregular heart urchins to sand dollars and sea biscuits. The echinoid fossil record extends to the Ordovician (approximately 450 Ma), and the group survived all five major mass extinctions. Irregular echinoids — including heart urchins and sand dollars — evolved from regular ancestors during the Jurassic and have been particularly successful since the Cretaceous. Living species closely related to common fossil genera like Echinocorys and Micraster are found in shallow marine sediments around much of the world today, demonstrating the remarkable longevity of the echinoid body plan.