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Temporal range: Lower Jurassic–Holocene
Scientific classification
Kingdom: Animalia
Phylum: Echinodermata
Class: Echinoidea
Superorder: Neognathostomata
Order: Cassiduloida
L. Agassiz & Desor, 1847


Cassiduloida is an order of sea urchins. The group was extremely diverse with many families and species during the Mesozoic, but today, only a few species survive.

Description and characteristics[edit]

Cassiduloids have a rounded or slightly oval appearance, and look somewhat similar to heart urchins, although they are actually more closely related to the sand dollars. They are distinguished from other sea urchins by the presence of smaller intervening areas between the main ambulacral areas on the oral surface. They have no lantern as adults, and the petaloids are poorly developed or absent.

List of families[edit]