Tritonidoxa Bergh 1907 (Figs 3D, 4D, 5D, 6D)

Type species: Tritonidoxa capensis Bergh 1907, by original designation. To date, this is a monotypic genus.

Diagnosis: Penis long, spiralled with pointed end. Secondary gills abscent; notal margin distinct, broad and wrinkled.

Morphology: Body slightly broad, length up to 32 mm. Notum smooth, with transverse white patches from head to tail. Oral veil narrow and entire. Eight simple velar processes. Secondary gills absent. Notal margin distinct, broad and wrinkled (Fig. 3D). Ratio jaw/body length: 0.20–0.35. Rachidian tooth tricuspid and smooth with a rectangular base (Fig. 4D). First lateral tooth differentiated, broad, smooth and sharp. Masticatory borders of jaws denticulate, with medium-sized (up to 40 µm) denticles with conical bases and sharp cusps. Cuticular folds absent. ODG complex holohepatic (Fig. 5D). Gonopore at one-third of body length, furthest from rhinophores. Anus and nephroproct aħer middle of body length. Bursa copulatrix reniform. Penis flagelliform long (up to 30 mm), spiralled with pointed end (Fig. 6D). Ampulla slightly pyriform (Fig. 6D).

Remarks: For the first time since its description, the monotypic species Tritonidoxa capensis is reassessed, and its taxonomic validity confirmed. Tritonidoxa was recovered as the sister-taxon of Tritonicula (PP = 1; BS = 98) (Fig. 2), but the two genera are morphologically different: Tritonicula species. are smaller and have a distinct first lateral tooth and reproductive morphology. The morphological synapomorphies of Tritonidoxa are the spiralled, long penis (up to 30 mm) with a pointed end (Fig. 6D) and absence of secondary gills, with the notal margin distinct, broad and wrinkled. To date, there is no further knowledge about the distribution and ecology of this aberrant species.