Gyneleucon, Brito & Serejo, 2023

Brito, Ayrton Do Ramo & Serejo, Cristiana Silveira, 2023, Leuconidae Sars, 1878 (Crustacea: Cumacea) from the southwestern Atlantic, filling the distribution gap along the Brazilian coast, Zootaxa 5383 (2), pp. 101-134 : 125

Genus Gyneleucon gen. nov.

Diagnosis (only male). Carapace dorsally unarmed; pseudorostrum slightly dorsally directed.Antenna 1 geniculated between articles 1 and 2. Antenna 2 flagellum extending until pereonite 2, brush setae on articles 4 and 5 outer margin. Mandibles leuconid-like. Pereopod 2 ischium absent. Only pereopods 1–3 with exopods. Penial lobes absent. Pleopods absent. Uropodal endopod with 2 articles. Females unknown.

Type species: Gyneleucon tripedium gen et sp. nov.

Etymology: the name comes from Gyne (old Greek: woman) + Leucon (radical of family), as mature male specimens of the genus look similar to typical leuconid females.

Remarks: The genera Gyneleucon gen. nov. has a similar habitus to Leucon and shares many characters with Hemileucon Calman, 1907 , such as: antenna 1 geniculated between articles 1 and 2; antenna 2 peduncle articles 4 and 5 with brush setae on outer margin; antenna 2 flagellum extending until pereonite 2; penial lobes and pleopods absents; and uropodal endopod 2-articulate ( Watling 1991). On the other hand, Gyneleucon can be distinguished from Hemileucon by the absence of ischium at pereopod 2 (versus present), and exopods at pereopods 1–3 in males, a unique character among the family (versus exopods on pereopods 1–4 in males) ( Watling 1991).

Unfortunately, all specimens of Gyneleucon gen. nov. were lost in the 2018 fire at Museu Nacional/UFRJ, and no specimens were subsequently found. This raises doubts about some previously observed characters, such as the number, type, and location of certain setae on the appendages, as well as the presence of the ischium on pereopod 2. However, the presence of exopods only on pereopods 1–3 in males is unquestionable and unique among the family. All five specimens observed showed no exopod (or insertion mark) on pereopod 4.

Despite the loss of the type material, we decided to publish the new species.According to the International Code of Zoological Nomenclature, if the holotype no longer exists, the designation of the species will not become invalid. Article 73.1.4 states that “designation of an illustration of a single specimen as a holotype is to be treated as a designation of the specimen illustrated; the fact that the specimen no longer exists or cannot be traced does not itself invalidate the designation” (ICZN 1999). All species were herein examined, registered and with descriptions and illustrations made before the fire. This follows ICNZ recommendation 73B, which states “preference for specimens studied by author. An author should designate as holotype a specimen actually studied by him or her, not a specimen known to the author only from descriptions or illustrations in the literature” (ICNZ 1999). Previously, new species of Hexapoda and Cumacea with types lost in the Museu Nacional fire have been published under Article 73.1.4 and Recommendation 73B of ICNZ 1999 ( Marinho et al. 2019; Vivallo 2019; Brito & Serejo 2020).