Rediscovery of the holotype of the Tongue Sole, Cynoglossus dollfusi (Chabanaud, 1931): Its impact on Red Sea records for C. sealarki Regan, 1908, C. lingua Hamilton, 1822, and C. zanzibarensis Norman, 1939, and on the taxonomic status of C. cleopatridis Chabanaud, 1949 (Pisces: Pleuronectiformes: Cynoglossidae).

Considerable confusion has surrounded the identity of the nominal species, Paraplagusia dollfusi Chabanaud, 1931, known only from two specimens: the holotype, collected in Gulf of Suez, Red Sea, and a second, non-type specimen (reported with the trinomial Cynoglossus (Trulla) dollfusi) captured in the Suez Canal, Red Sea. No catalogue number, illustration or photograph of the type specimen accompanied the original description, which also lacked critical information to confidently assign this species to a genus or to diagnose it from previously described tongue soles possessing similar attributes. Both the type and non-type specimen have been reported as lost for over 40 yr, further confounding attempts to resolve questions regarding the identity and status of this nominal species. During its history, C. dollfusi has been considered as a junior subjective synonym of C. sealarki Regan, 1908, a senior subjective synonym of C. cleopatridis Chabanaud, 1949, and has been misidentified as C. zanzibarensis Norman, 1939. The trinomial, Cynoglossus (Trulla) dollfusi, has also been considered as a second nominal species. Recently, specimens currently curated in the same jar in the fish collection of the Muse´um National d’Histoire Naturelle (Paris) and identified as C. zanzibarensis collected in the Red Sea were determined to be the missing holotype of P. dollfusi Chabanaud, 1931 and the second-known specimen of C. dollfusi. Their sizes, as well as their meristic and morphometric features, agree with those provided in the original description of the holotype of C. dollfusi and for those in the account of the second specimen. Rediscovery of the holotype confirms the validity of this species. Based on the holotype and non-type specimen and information from the literature, C. dollfusi is redescribed and diagnosed from other Indo-West Pacific species of the genus. Information from these two specimens also provides the necessary data to resolve historical problems regarding the identity and taxonomic placement of this species. Additionally, this new information resolves Red Sea distributional records for three other species of Cynoglossus. Conclusions from the present study indicate: a) Chabanaud erred in placing his nominal species dollfusi in the genus Paraplagusia. New data allow confident assignment of this species to Cynoglossus. b) The hypothesis that two nominal species are represented by the names P. dollfusi and Cynoglossus (Trulla) dollfusi is unsupported. Cynoglossus (Trulla) dollfusi is a new combination reflecting transfer of dollfusi from Paraplagusia to Cynoglossus. c) The hypothesis that C. dollfusi (Chabanaud, 1931) is a junior subjective synonym of C. sealarki is not supported by the data. These two species differ significantly to warrant recognizing both as valid. d) C. dollfusi has erroneously been considered the senior synonym of C. cleopatridis Chabanaud, 1949, a nominal species known only from a damaged holotype also collected in the Red Sea. Cynoglossus dollfusi was redescribed in a global revision of the genus based mostly on information from the holotype of C. cleopatridis, a decision that significantly changed the species concept of C. dollfusi from that intended in the original description. e) The hypothesis that C. cleopatridis Chabanaud, 1949 is a junior subjective synonym of C. dollfusi (Chabanaud, 1931) is rejected. The holotype of C. cleopatridis differs sufficiently in several meristic and morphometric features to demonstrate that C. dollfusi and C. cleopatridis are distinct species. f) Additional specimens are needed to more completely understand the nominal species, C. cleopatridis. g) The specimen thought to voucher C. lingua Hamilton, 1822 from the Red Sea was misidentified. It later became the holotype of C. cleopatridis, a species quite distinct from C. lingua. h) The list of cynoglossine fishes reported from the Red Sea has been updated. Red Sea records of P. dollfusi Chabanaud, 1931 should be emended to C. dollfusi (Chabanaud, 1931). The only specimens thought to voucher Red Sea records for C. sealarki, C. zanzibarensis, and C. lingua were all misidentified. Therefore, these species are removed from the list of tongue soles occurring in the Red Sea. [ABSTRACT FROM AUTHOR]