Homalozoa

Article By:

Sprinkle, James Department of Geological Sciences, University of Texas, Austin, Texas.

Last reviewed:January 2020

DOI:https://doi.org/10.1036/1097-8542.321300

Enigmatic extinct echinoderms whose members are characterized by a flattened body form and the complete lack of pentameral (five-sided radial) symmetry. Previously considered the fifth subphylum of echinoderms, homalozoans (commonly called carpoids) originally included four extinct classes of early echinoderms that had a theca or body protected by calcite plates showing diagnostic stereom (a unique skeletal microstructure resembling a network or mesh of interconnected holes). About 92 homalozoan genera have been described, assigned to the following classes: Stylophora (also called Calcichordata), including the two orders Cornuta (Middle Cambrian–Late Ordovician) and Mitrata (Early Ordovician–Early Pennsylvanian), with a total of about 66 genera; Soluta (also called Homoiostelea; Middle Cambrian–Early Devonian), with 12 genera; Cincta (also called Homostelea; Middle Cambrian), with 11 genera; and Ctenocystoidea (Middle Cambrian), with three genera. See also: Echinodermata

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