Enodicalix (Diploporita, Aristocystitidae): A new echinoderm genus from the Middle Ordovician of Spain.

Restudy of an Ordovician diploporite specimen from the Middle Ordovician of central Spain reveals that the species 'Calix' inornatus MELENDEZ has four ambulacra, each with two equal facets, an oval hydropore and a smooth thecal surface. In contrast, the type species of Calix has four ambulacra, each with four facets added in a clockwise direction during growth, a trilobed hydropore, and a theca with spiny plates. Other aristocystitid genera with four ambulacra have one facet per ambulacrum. 'Calix' inornatus differs from all other aristocystitid genera and warrants a new generic name, for which we propose Enodicalix.