dcsimg

Diagnosis

provided by World Register of Marine Species
Centrodorsal thick to thin discoidal or pentagonal, rarely stellate; aboral apex broad, cirrus-free, flat or slightly convex or concave, sometimes with narrow, radiating, interradial impressions; aboral star absent, but center of aboral apex sometimes depressed; centrodorsal cavity less than 30% of centrodorsal diameter, larger in very small specimens; adoral surface with interradial furrows for basals, but no radial pits or coelomic impressions. Cirrus sockets generally rather large, without distinct ornament, crowded around centrodorsal margin in 1-3 irregular tiers, never forming vertical columns. Some species of Comatula, Comanthus, Comaster, Phanogenia and Capillaster with centrodorsal thin, reduced, commonly not projecting below radials and bearing few or no cirri. Basals forming rosette with rod-like rays, commonly exposed interradially. Subradial clefts may be present, especially in large specimens. Exposed aboral surface of radials usually short, sometimes partly or completely oncealed; well exposed in species with reduced centrodorsal. Radial articular facet parallel to oral-aboral axis or nearly so and with shallow fossae. Interarticular ligament fossae large, high and wide, generally higher than aboral ligament fossa and separated by broad, shallow midradial furrow. Adoral border of interarticular fossae straight or slightly curved, horizontal or slightly sloping. Adoral muscle fossae low, always smaller than interarticular ligament fossae, forming narrow bands along horizontal adoral edge. Radial cavity large, with spongy calcareous filling in living specimens. Rays divided at least at primibrachial 2, commonly up to several times more and producing as many as 180 undivided arms. Synarthry between primibrachials 1-2 and secundibrachials 1-2, or modified synarthry either relatively featureless or resembling syzygies. True syzygies present only in Comatula. First pinnule on secundibrachial 2 (when series composed of 4 ossicles). Oral pinnules slender, flagellate, of numerous short pinnulars. Distal pinnulars of at least some oral pinnules bearing a comb formed by peg- or bladelike teeth, 1-2 per pinnular. Middle and distal pinnules commonly extremely spiny. Arms arising farthest away from eccentrically placed mouth (=posterior) commonly shorter than those arising closest to mouth, sometimes lacking ambulacral groove but with better developed gonads. Mouth typically displaced off center or marginal, and anal papilla central or subcentral on disk (commonly less so in juveniles); mouth central or subcentral in several genera. (As Comasteroidea; modified from Hess & Messing, 2011.)
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copyright
WoRMS Editorial Board
bibliographic citation
Hess H, Messing CG (2011) Comatulida. In: Hess H, Messing CG, Ausich WI. Treatise on Invertebrate Paleontology, Part T, Echinodermata 2 Revised, Crinoidea, vol. 3. University of Kansas Press, Lawrence, Kansas, pp. 70–146.
contributor
Charles Messing [email]
contributor
Charles Messing [email]