Since 2012, when Ophiothela was first described in the Atlantic, there has been no consensus regarding its identification. It has been described as O. mirabilis, O. cf. mirabilis, O. danae, or only Ophiothela sp. In order to fill these gaps, our aim was to test if specimens from Brazil are Ophiothela mirabilis and/or Ophiothela 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 star Ophiothela using independent character sets utilizing morphology (external morphology and morphometry) and molecular data (16S and COI). Concordance was found between the analyses indicating that Ophiothela sp. from Brazil (BR), Ophiothela mirabilis and Ophiothela danae are closely related. We suggest that O. danae should be considered as a junior synonym of O. mirabilis. A detailed description of O. mirabilis BR 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 in Ophiothela); (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 species Ophiactis savignyi and Ophiocomella ophiactoides).

The genera Ophiophragmus and Amphiodia are amphiurids that are considered taxonomically difficult due to their great resemblance, few diagnostic characters and synonymy problems. Our aim is to redescribe the species using scanning electron microscopy and morphometry of diagnostic structures, and to provide new information for the identification of these Ophiuroidea. Five Amphiodia spp. and six Ophiophragmus spp. recorded in Brazil were rigorously redescribed. The descriptions include new diagnostic characters derived from external morphology, arm microstructures and morphometry. We also provided comparative analyses of species with shared characters such as Amphiodia riisei and Amphiodia trychna. The geographic and bathymetric distributions of the studied species were updated, and new records are provided. All the information presented may be used in taxonomic, ecological and phylogenetic studies, helping to fill gaps in the knowledge of the biodiversity, ecology and evolution of these Ophiuroidea. Conclusively, all the tools applied here assisted in the identification of genera and species and could be useful in other taxonomic studies of Echinodermata.

Este trabalho tem por objetivo o reconhecimento seguro das espécies do gênero Ophiothela oriundas de duas ecorregiões na costa brasileira. O estudo se fez necessário pois os espécimes apresentam muitas sobreposições de caracteres morfológicos e com diferentes padrões de coloração, dificultando a identificação por meio da taxonomia tradicional. Por isso, os exemplares foram estudados com base na análise do gene mitocondrial 16S. Os testes de relações filogenéticas mostraram a existência de, pelo menos, duas linhagens, porém com baixa distância genética entre elas. Estas linhagens não estão relacionadas com os diferentes padrões de coloração encontrados, ecorregiões, pontos de coleta ou substrato biológico.

Este trabalho tem por objetivo a revisão taxonomica do gênero Ophiothela, analisando espécimes do Brasil e Estados Unidos. O estudo se fez necessário devido a sobreposição de caracteres morfológicos, dificultando o reconhecimento da espécie pela taxonomia tradicional. Por isso os exemplares foram estudados com base na análise dos genes mitocondriais 16S e COI. Os resultados obtidos pela distância genética e Análise de Variância Molecular (AMOVA) indicam que os grupos são geneticamente distintos e bem estruturados, indicando baixo ou nulo fluxo gênico entre eles. Sendo assim provavelmente Ophiothela sp. do Brasil representa uma linhagem diferente da Flórida.