Taxonomic analysis of the genital plates and associated structures in Ophiuroidea (Echinodermata) Author Stöhr, Sabine 412800EB-AACE-4313-9810-61F89B740405 Swedish Museum of Natural History, Department of Zoology, Box 50007, 10405 Stockholm, Sweden. sabine.stohr@nrm.se text European Journal of Taxonomy 2024 2024-05-14 933 1 98 https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/2525/11335 journal article 10.5852/ejt.2024.933.2525 2118-9773 11198874 8F720F2B-BFBC-4CA1-BFF2-A2B8C7C8D3E1 Genus Ophiothrix Müller & Troschel, 1840 Fig. 29 Type species Asterias fragilis Abildgaard in O.F. Müller, 1789. Examined species Ophiothrix fragilis . Oral GP Oval scale-like, thin, as long as OS, some with notch in proximal part of ventral edge. Pair at acute angle, to either side of distal lobe on OS, half covered by OS. Visible through skin as v-shaped pair of ossicles, supporting proximal end of genital slits. Adradial GP Bar-like with bulbous distal end, curved with dorsal edge concave, ventral edge convex. Slanting away from arm, not completely vertical. Large, round, knob-like condyle at distal end bordered by deep groove meets similar condyle on underside of radial shield. Proximal to condyle several other protrusions and fine meshed stereom patches. Abradial GP Half-circle to kidney-shaped, dorsal edge concave in middle, straight in proximal half, dorso-distal end with concave articular groove, ventral edge strongly convex. Articulated with adradial GP by elongated depression. Almost dorsoventrally horizontal, only slightly downward slanting. Dorsal surface with radiating striations, ventral surface without. Oral shields Oral shield with distal lobe, to which at either side an oral GP attaches. Madreporite bulging in centre, with large central opening. Radial shield Large distal condyle, bordered by curved groove, proximal to condyle a kidney-shaped patch of smooth, finer meshed stereom. Fig. 29. Ophiotrichidae Ljungman, 1867 , Ophiothrix fragilis (Abildgaard in O.F. Müller, 1789), SEM, unless otherwise noted. A . Genital plates and radial shield inside disc, micro-CT. B . Genital plates in situ, ventral aspect. C . adGP, abradial aspect. D . adGP, adradial aspect. E . abGP, abradial aspect. F . abGP, adradial aspect. G . Radial shield, internal aspect. H . Madreporite, internal aspect. I . Oral shield, internal aspect. J . oGP (arrowheads) in situ, ventral aspect, digital image. K . Same, internal dorsal aspect. L . oGP. Scale bars: A–G, J–K =1 mm; H–I, L=0.5 mm. Remarks In Ophiothrix , the oral GP are more obvious than in most other here examined genera, strong and large plates, in contrast to the small, thin scales covering the soft ventral disc.