Retrovescus, a new genus of opisthogastric earthworm from Tasmania

Abstract

The earthworm genus Retrovescus, gen. nov. isestablished to accommodate four uncommon species with distributions restrictedto the north-west of Tasmania. The type species isRetrovescus plomleyi, sp. nov., two other species arenewly described while the fourth, R. capensis (Jamieson,1974), is redescribed and errors in the original account are corrected. A keyis provided. Characteristic traits, all apomorphies, are perichaetine setae,tubulo-racemose prostates, avesiculate meroic nephridia and opisthogastry (thedevelopment of intestinal gizzards, which in this genus are multiple in theregion of segments 20–26). Relationships and possible precursors toRetrovescus and to a sympatric genus,Nexogaster Blakemore & Kingston, 1997, which differsprincipally by its lumbricine setae and well developed typhlosole, arediscussed.