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 Family LEUCONIDAE Sars, 1878 Diagnosis . Fused pleotelson. Eyes absent (except the genus Ommatoleucon Watling 1991 ). Mandible with triangular base, molar process wide and setal row on incisor with two distal setae. Exopods at least in pereopods 1–2. Males with 0–2 pairs of pleopods, if present, endopodal process absent. Uropodal endopod, 1 or 2-articulate. Remarks : Leuconidae , Bodotriidae and Nannastacidae form a monophyletic clade with a fused pleotelson ( Gerken et al. 2022 ). Within this clade, only Leuconidae has the mandible type cited as above with the combination of other characters ( Gerken et al. 2022 ; Heard et al. 2007 ).