Clypeasteroida

Article By:

Mooi, Rich Department of Invertebrate Zoology and Geology, California Academy of Sciences, San Francisco, California.

Last reviewed:December 2019

DOI:https://doi.org/10.1036/1097-8542.900668

The name originally given by Louis Agassiz in 1835 to a natural (monophyletic) group of echinoids (sea urchins and allied forms) containing animals variously known as sea pancakes, sea biscuits, cake urchins, sun dollars, sand dollars and keyhole urchins. Like all echinoderms, members of the order Clypeasteroida (clypeasteroids) are exclusively marine species, distributed on continental shelf habitats throughout the world, except in Antarctic regions. There are approximately 250 extant species of clypeasteroids and another 750 nominal species described from the fossil record. Clypeasteroid taxa are arranged in three major groups (suborders): Clypeasterina (sea pancakes, sea biscuits and cake urchins; families Clypeasteridae and Arachnoididae); Laganina (sometimes called sun dollars; families Laganidae and Fibulariidae); and Scutellina (the true sand dollars and keyhole urchins; families Echinarachniidae, Dendrasteridae, Astriclypeidae and Mellitidae). See also: Echinodermata; Echinoidea

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