Integrative taxonomy suggests hidden diversity within the fish genus Cyttopsis (Zeiformes, Parazenidae).

Nine specimens of Cyttopsis rosea (Zeiformes: Parazenidae) were collected during scientific surveys at three different locations in the northeast Atlantic. All nine specimens were included in the molecular analysis, adding new cytochrome c oxidase subunit I sequences to public databases. Of these, six specimens were retained for detailed morphological examination. Morphological measurements and counts agree with previous descriptions and confirm the identification of C. rosea. However, molecular species delimitation analyses suggested cryptic diversity, identifying three molecular operational taxonomic units, contrary to the current status of a single species with a worldwide distribution. The integration of classical and molecular taxonomy proved essential for accurately delimiting and characterizing this species, enhancing our understanding of its intraspecific morphological and molecular variability. A literature review of the available morphological data of Cyttopsis rosea between Atlantic and Pacific specimens showed differences in the caudal peduncle length, number of vertebrae and the number of scales in the lateral line, which could support the existence of different species. Based on the resulting data and the available literature, an updated key of the accepted members of the family Parazenidae is provided.