Leuconidae Sars, 1878 (Crustacea: Cumacea) from the southwestern Atlantic, filling the distribution gap along the Brazilian coast Author Brito, Ayrton Do Ramo Setor de Carcinologia, Museu Nacional / Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, São Cristóvão s / n, 20940 - 040, Rio de Janeiro, Brazil & Programa de Pós-graduação em Ciências Biológicas (Zoologia), Museu Nacional / Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, São Cristóvão s / n, 20940 - 040, Rio de Janeiro, Brazil Author Serejo, Cristiana Silveira Setor de Carcinologia, Museu Nacional / Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, São Cristóvão s / n, 20940 - 040, Rio de Janeiro, Brazil & Programa de Pós-graduação em Ciências Biológicas (Zoologia), Museu Nacional / Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, São Cristóvão s / n, 20940 - 040, Rio de Janeiro, Brazil text Zootaxa 2023 2023-12-11 5383 2 101 134 https://www.mapress.com/zt/article/download/zootaxa.5383.2.1/52444 journal article 10.11646/zootaxa.5383.2.1 1175-5326 10350586 996315A6-A209-4DF7-B59C-0B7662741F37 Subgenus Alytoleucon Watling, 1991 Diagnosis. Branchial syphon extending as long as or slightly longer than pseudorostrum. Antenna 1 accessory flagellum rudimentary. Pereonite 5 without ventral hooks, mature males may present penial lobes. Uropodal endopod terminal setae fused to article (modified from Watling, 1991 ). Type species: Leucon jonesi Bishop, 1982 Remarks. The presence of penial lobes in the family Leuconidae is common, and can be found in species of Afroleucon Mühlenhardt-Siegel, 2011 , Kontiloleucon Gerken, 2016 , Phalloleucon Mühlenhardt-Siegel, 2008 and in the species Eudorella redacticruris Watling and McCann, 1997 . In the present study it was noticed the presence of penial lobes in Leucon ( Alytoleucon ) . Mature males of Leucon ( Alytoleucon ) rhuanae n. sp. present a small tube-like pair of penial lobes similar to Afroleucon enigmatica Mühlenhardt-Siegel, 2011 . Bishop (1982a) has already mentioned penial lobes in mature males of L. ( A ) jonesi . Penial lobes might be present in all mature males of Leucon ( Alytoleucon ) , but that needs further investigation.