Pawson, David L Department of Invertebrate Zoology, Smithsonian Institution, Washington, DC.
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An order of sea urchins (class Echinoidea) with a large elevated apical disc that covers about one half of the upper surface of the test. The center of the disc in Salenioida has one or more large suranal plates covering the anus, which is slightly posterior in position. Ambulacral plates are very small compared with the interambulacral plates, and the pore pairs for the tube feet are arranged in groups of one, two, or three. Each interambulacral plate has a single large primary tubercle, which is crenulate and may be perforate or imperforate. The lantern (feeding and locomotor apparatus) is of the stirodont type, with the apophyses not connected at the upper end, and with keeled teeth that are T-shaped in cross section. Some years ago, two families were recognized in the Salenioida: (1) Acrosaleniidae, which included approximately six fossil genera, ranging from the Upper Triassic or Lower Jurassic to the Cretaceous of Europe, Africa, Asia, and the Caribbean; and (2) Saleniidae, with about 10 genera, ranging from the Upper Jurassic to the Recent (two extant genera) in many parts of the world. The family name Acro saleniidae has been abandoned by several authors in favor of an informal grouping—the acrosaleniids. See also: Echinodermata; Echinoidea
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