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 Ophiomyces Lyman, 1869 Fig. 12 Type species Ophiomyces frutectosus Lyman, 1869 . Examined species Ophiomyces delata Koehler, 1904 , O . frutectosus . Oral GP Not examined, not identified in situ. Considered absent. Adradial GP Flat, thin, blade-like, ventral edge convex, dorsal edge straight, articular structure at distal end as embossed oval patch with finer stereom. Fig. 12. Ophiohelidae Perrier, 1893 . A–B . Ophiomyces frutectosus Lyman, 1869 , digital photos. A . Lateral view. B . Detail of genital plates in situ. C–H . Ophiomyces delata Koehler, 1904 , SEM. C . adGP, abradial aspect. D . abGP, adradial aspect. E . Genital plates in situ. F . Oral shield, external aspect. G . Oral shield, inner aspect. H . Madreporite, inner aspect. Scale bars: A–B =1 mm; C–E =0.5 mm; F–H=0.1 mm. Abradial GP Similar to adGP, articular patch depressed. When both GP are articulated, they are parallel, leaving a narrow slit between them. Oral shields Minute, elongated drop-shaped, with thickened rectangular distal end, depressed center of OS with coarse, porous stereom in external and internal views. Madreporite similar, with several small pores in middle part. Radial shield Absent. Remarks Matsumoto (1915 , 1917 ) considered the abradial genital plate (his “genital scale”) and the radial shield in Ophiomyces to be absent ( Table 1 ). Lyman (1882) considered the radial shield to be absent, but both genital plates to be present ( Table 1 ), and the present study confirms his interpretation. They both described the adradial genital plate as curved over the top of the arm. Instead, both genital plates are flat and straight, and in the intact disc they may be upright or diagonal across the arm base ( Fig. 12E ). Oral GPs were not found after dissociating the skeleton and may be absent, since the adGP and abGP extend the full length from oral shield to disc edge, with the genital slit opening between them. Conditions in Ophiotholia spathifer (Lyman, 1879) are the same as in Ophiomyces .