Spirostreptus tripartitus Cook & Collins 1893

Figs 4, 7 f

Spirostreptus tripartitus Cook & Collins 1893, p. 31, figs 17–22; Hoffman 2008 Triaenostreptus tripartitus: Attems 1928; Hoffman 1971; Krabbe 1982

Type material: Syntypes: CONGO: 2 3 (USNM 2384).

Additional material examined: ANGOLA: 1 3, Egito near Benguela [12 0 33'S, 13 0 24'E], 1975, (ZMUC uncatalogued).

Diagnosis: Gonopods with angular distal lobe, and with oral surface with folds and a prominent diagonal groove; distal lobe length equal to width (Fig. 4 a).

Description: Size: Body length 176 mm; minimum and maximum body width 7–9 mm and 11–14 mm.

Number of body rings: 66–72.

Colour: Body black or brown; legs and antennae red-brown.

Collum: With narrow anterior lobe slightly produced ventro-laterally, 3–4 complete folds and an incomplete fold (Fig. 4 d).

Pre-femoral process of 1st pair of male legs: Proximally rounded, with a long slightly laterally deflected nipple (Fig. 4 c).

Gonopod: (Figs 4 a, 4b) 6 mm long. Sternite short, not reaching the level of paracoxite apex.

Telocoxites parallel, not touching, wider apart distal to sternite apex (at the level of proplica apex).

Proplica wide and angular subapically (Fig. 4 a).

Metaplica wider proximal to telopodite knee, distally metaplica with small horizontal hump, raised medial edge and a small central, conical apex giving a two prong appearance.

Lateral lobe tightly fused to distal lobe and apical proplica, folded and rounded distally. Lateral lobe extending slightly beyond the lateral edges of subapical proplica and distal lobe.

Distal lobe extends to or beyond the lateral edge of proplica apex, lobe as long as it is wide. Orally, distal lobe surface with folds and a deep diagonal groove (Fig. 4 a). Distal lobe overlaps lateral lobe proximally.

Telopodite with crescent-shaped antetorsal process which does not extend to or past paracoxite apex, strongly bent medially but not crossing metaplica (Figs 4 a, 4b, 7f); post knee telopodite with loose spiral.

Distribution: Benguela, west coast of Angola and from an unknown locality in Democratic Republic of Congo.

Remarks: Gonopod morphology suggests that tripartitus is closest to sebae . Like sebae, the distal lobe has surface folds, however, tripartitus is distinguished by a prominent diagonal groove (Fig. 4 a) on the distal lobe surface and the smaller size of the distal lobe. In sebae the distal lobe is wider (lateral width) than it is long and the apex is horizontal, unlike in tripartitus (see remarks on sebae).

According to the literature (Krabbe 1982) the holotype of S. tripartitus is in the United States National Museum, Washington, USA. However, only a syntype was made available for examination. Therefore the syntype, material from Angola and the original description were used in the study.