New Parabathynellidae species in Africa: the first bathynellids from Chad and an assay of their phylogenetic position in the order Bathynellacea (Crustacea: Malacostraca) based on 18S sequences

Abstract

Two new species of the genera Haplophallonella Serban and Coineau, 1975a and Racovitzaibathynella Serban and Coineau, 1994 are described from Africa. This is the first record of the members of the order Bathynellacea Chappuis, 1915 from Chad. Representatives of the genus Haplophallonella have hitherto been known only from the Ivory Coast type locality, and Racovitzaibathynella only from South Africa. Representatives of Haplophallonella irenae sp. nov. and Racovitzaibathynella dumonti sp. nov. have a unique combination of morphological characters. Haplophallonella irenae sp. nov. includes: seven-segmented antennule; five-segmented antenna; labrum with special morphology, clefted; mandible without proximal tooth; no epipodite on thoracopod I; bidentated exopod of male thoracopod VIII; triangular female thoracopod VIII; presence of basal seta on exopod of uropod and three plumose setae on endopod of uropod. Racovitzaibathynella dumonti sp. nov. includes: seven-segmented antennule; five-segmented antenna with sexual dimorphism and without seta on segment two; no epipodite on thoracopods I and II; outer lobe of male thoracopod VIII almost square, does not cover the posterior part of dentate lobe; the posterior lobe covers one part of dentate lobe, exopod with pointed distal end, basipod with distal end bilobed and endopod as two unequal smooth setae; almost triangular female thoracopod VIII and five to seven similar spines on sympod of uropod. Sequences of the 18S ribosomal RNA (rRNA) gene from 12 specimens of Racovitzaibathynella dumonti sp. nov. and two specimens of Haplophallonella irenae sp. nov. were obtained and analysed to complete the morphological description with molecular data. We have used these data to make a preliminary phylogenetic analysis with all genera of the world for those whose sequences are available (18S). Phylogenetic reconstruction of the Parabathynellidae family shows how the new African species remain clearly separated from European and Australian genus groups.