Article
Article
Hemicidaroida
Article By:
Smith, Andrew B. Department of Paleontology, Natural History Museum, London, United Kingdom.
Last reviewed:2012
DOI:https://doi.org/10.1036/1097-8542.313200
An extinct paraphyletic order of regular sea urchins (Echinoidea), identified by having a plain, unsculptured test, tubercles that are perforate and crenulate, and no suranal plate intercalated into the apical disc. They almost certainly include ancestors of later groups that developed imperforate and noncrenulate tuberculation and are thus paraphyletic.
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