Unravelling the taxonomic identity ofOphiothelaVerrill, 1867 (Ophiuroidea) along the Brazilian coast

Since 2012, whenOphiothelawas first described in the Atlantic, there has been no consensus regarding its identification. It has been described asO.mirabilis,O. cf.mirabilis,O.danae, or onlyOphiothelasp. In order to fill these gaps, our aim was to test if specimens from Brazil areOphiothela mirabilisand/orOphiothela danae. Syntypes from the Museum of Comparative Zoology and United States National Museum, Smithsonian Institution, were used. We examined species boundaries of the small six-rayed brittle starOphiothelausing independent character sets utilizing morphology (external morphology and morphometry) and molecular data (16S and COI). Concordance was found between the analyses indicating thatOphiothelasp. from Brazil (BR),Ophiothela mirabilisandOphiothela danaeare closely related. We suggest thatO.danaeshould be considered as a junior synonym ofO.mirabilis. A detailed description ofO.mirabilisBR is presented using external morphology and microstructural ossicles (arm plates, vertebra, dental and oral plates). This description includes new diagnostic features, particularly regarding its microstructures: (i) transspondylous articulation (first record in Ophiotrichidae); (ii) eight smooth knobs on the dorsal surface of the vertebrae (to date only inOphiothela); (iii) vertebrae with distal keel divided into two separate end processes matching the two large dorsal grooves proximally (first time in the literature); and (iv) an opening on both sides of the oral plate (as seen in other fissiparous speciesOphiactis savignyiandOphiocomella ophiactoides).