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Antedon
''Antedon'' is a genus of free-swimming, stemless crinoids. The genus first appeared in the fossil record in the Cretaceous period.〔(''Antedon pinnulata '' ) The Fossil Museum. Retrieved 2011-10-13.〕 ==Characteristics== Members of this genus have no stems but have five pairs of feathery arms arising from a central concave disc. There are a number of cirri or unbranched appendages on a low, cone-shaped dorsal ossicle, a bone-like structure in the centre of the disc. The mouth and the ambulacral grooves are also on the upper surface. Clawed cirri on the lower surface provide temporary attachment to the substrate.〔(Family Antedonidae ) Marine Species Identification Portal. Retrieved 2011-10-13.〕 There is great variability in the morphological features in Antedonids found in different habitats and the main distinguishing feature among the species is the number of cirri.
抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Antedon」の詳細全文を読む
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