Cassiduloida is an order of sea urchins. The group was extremely diverse with many families and species during the Mesozoic, but today, only seven extant species remain.
A 2019 phylogenetic systematics study by Souto et al. presented a revised classification of the cassiduloids, and hypothesised that the order probably originated in the Early Cretaceous.
Description and characteristics 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 and genera family Cassidulidae L. Agassiz and Desor, 1847 genus Cassidulus Lamarck, 1801 genus Paralampas Duncan & Sladen, 1882 genus Rhyncholampas Agassiz, 1869 family Eurhodiidae Souto et al., 2019 genus Australanthus Bittner, 1892 genus Eurhodia d'Archiac & Haime, 1853 genus Glossaster Lambert, 1918 genus Kassandrina Souto & Martins, 2018 family Faujasiidae Lambert, 1905 family Neolampadidae Lambert, 1918 family Pliolampadidae Kier, 1962 † family Galeropygidae Lambert, 1911 † genus Galeropygus Kier (1962) † genus Eogaleropygus Kier (1962) †
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