Gnathia lancifera, Botha & Smit & Erasmus & Hadfield, 2025

Gnathia lancifera sp. nov.

Figs 10 View Figure 10 , 11 View Figure 11 , 12 View Figure 12 , 13 View Figure 13

Not Gnathia spongicola View in CoL — Smit 1997: 98–112

Material examined.

Holotype. South Africa • 1 ♂ ( 4.1 mm); east of Lake St Lucia ; 27°59.5'S, 32°40.8'E; depth 550 m; 22 May 1976; RV Meiring Naude; dredge ( SAMC A 099276 ) GoogleMaps .

Paratype. South Africa • 1 ♂ (damaged); with the same data as holotype ( SAM A 19326 ) GoogleMaps .

Description of adult male.

Body (Fig. 10 A View Figure 10 ) 2.3 times as long as greatest width, widest at pereonite 3; dorsal surfaces anteriorly with tubercules, sparsely setose. Cephalosome (Fig. 10 B View Figure 10 ) 0.8 times as long as wide; lateral margins narrowing posteriorly; posterior margin slightly concave; dorsal surface with numerous granules; dorsal sulcus wide, deep, extended; translucent region absent; para-ocular ornamentation weakly developed and with several tubercles and setae; posterior median tubercle present. Frontolateral processes present. Frontal margin slightly produced, median point even. External scissura present, narrow, shallow. Mediofrontal process present, weak, rounded, without ventral notch, with fine setae. Superior frontolateral process present, single, strong, conical, with 1 pair of long simple setae. Inferior frontolateral process absent. Mesioventral margin slightly curved; granulated; anterior tip not dorsally visible. Supraocular lobe pronounced, rounded; accessory supraocular lobe not pronounced. Eyes present, 0.3 times as long as cephalosome length, bulbous, standing out from head surface, ommatidia arranged in rows.

Pereon lateral margins narrowing posteriorly from pereonite 3, with few setae; anteriorly with numerous fine granules. Pereonite 1 partially fused dorsally with cephalosome; dorsolateral margins fully obscured by cephalosome. Pereonite 2 wider than pereonite 1. Pereonite 4 without anterior constriction, median groove absent. Areae laterales present on pereonite 5; dorsal sulcus obscured by pereonite 6. Pereonite 6 with weak lobi laterales; lobuii weak, conical. Pereonite 7 not visible in dorsal view. Pleon covered in pectinate scales and epimera not dorsally visible on all pleonites. Pleonite lateral margins with 2 pairs of simple setae, with 1 pair of simple setae medially.

Pleotelson (Fig. 10 E View Figure 10 ) 1.2 as long as anterior width; lateral margins smooth, anterolateral margins weakly concave; posterolateral margin straight, with 1 pair of submarginal setae; apex with 2 setae.

Antennula (Fig. 10 C View Figure 10 ) shorter than antenna. Peduncle article 1 without tubercles; article 2 1.4 as long as article 1; article 3 2.2 as long as article 2, 3.8 as long as wide. Flagellum with 5 articles, as long as article 3; article 3 with 1 aesthetasc and 1 simple seta; article 4 with 1 aesthetasc seta; article 5 terminating with 1 aesthetasc and 2 simple setae. Antenna (Fig. 10 D View Figure 10 ) peduncle with 4 articles; article 3 3.7 as long as wide, 2 as long as article 2, with 1 penicillate seta and 3 simple setae; article 4 1.1 as long as article 3, with 4 penicillate setae. Flagellum with 7 articles, as long as article 4, 1.1 as long as article 3, terminating with 4 simple setae.

Mandible (Figs 10 E View Figure 10 , 13 B View Figure 13 ) crescent-shaped, strongly curved distally; apex 18.1 % total length; mandibular seta present. Carina present, smooth along proximal half. Incisor elevated, standing clear of surface, distal denticulation present. Blade present, straight, dentate along 82 % of margin. Dorsal lobe absent. Basal neck short. Erisma and lamina dentata absent.

Pylopod (Fig. 11 A View Figure 11 ) article 1 1.4 as long as wide, with three distinct areolae, without distolateral lobe; posterior and lateral margins forming rounded curve; lateral margin with 32 large plumose setae; mesial margin with continuous scale-setae; 4 surface simple setae present; distal margin with 8 simple setae; article 2 1.2 as long as wide, with 18 simple setae; article 3 (Fig. 11 B View Figure 11 ) minute, with 4 setae.

Maxilliped (Fig. 11 C View Figure 11 ) 5 - articled; article 1 lateral margin with continuous marginal scale-setae laterally; article 2 lateral margin with 5 plumose setae; article 3 lateral margin with 6 plumose setae; article 4 lateral margin with 5 plumose setae; article 5 with 8 plumose setae; endite extending to mid-margin of article 3.

Pereopods 2–6 (Fig. 12 View Figure 12 ) randomly covered in pectinate scales; inferior margins with prominent tubercles. Pereopod 2 (Fig. 12 A View Figure 12 ) with tubercles on basis to carpus; basis 2.2 as long as greatest width, superior margin with 4 setae, inferior margin with 4 setae; ischium 0.7 as long as basis, 2.4 as long as wide, superior margin with 3 setae, inferior margin with 4 setae; merus 0.4 as long as ischium, 0.9 as long as wide, superior margin with 3 setae, inferior margin with 2 setae; carpus 0.4 as long as ischium, 1.1 as long as wide, superior margin with 1 seta, inferior margin with 2 setae; propodus 0.6 as long as ischium, 2.7 as long as wide, superior margin with 1 simple seta and 2 robust setae; dactylus (with unguis) 0.8 as long as propodus. Pereopods 3 (Fig. 12 B View Figure 12 ) and 4 (Figs 12 C View Figure 12 , 13 E View Figure 13 ) mostly similar to pereopod 2; pereopod 5 (Fig. 12 D View Figure 12 ) similar to pereopod 6 (Fig. 12 E View Figure 12 ). Pereopod 6 with tubercles on merus and carpus and with tubercles on superior margin of basis; basis 3 as long as greatest width, superior margin with 6 simple setae, inferior margin with 6 setae; ischium 0.7 as long as basis, 2.8 as long as greatest width, superior margin with 4 setae, inferior margin with 8 setae; merus 0.5 as long as ischium, 1.8 as long as wide, superior margin with 2 setae, inferior margin with 3 setae, without dense patch of scale-setae; carpus 0.4 as long as ischium, 1.9 as long as wide, inferior margin with 1 seta; propodus 0.7 as long as ischium, 3.8 as long as wide, superior margin with 3 setae, and 2 robust setae; dactylus (with unguis) 0.5 as long as propodus.

Penes medially united.

Uropod rami extending beyond pleotelson apex, apices broadly rounded. Endopod 2.3 as long as greatest width, dorsally with 1 seta; lateral margin weakly sinuate, lateral margin with 3 simple setae; distomesial margin weakly convex, with 6 long plumose setae. Exopod extending to pleotelson apex, 4.3 as long as greatest width; lateral margin weakly sinuate, with 7 simple setae; distomesial margin convex, with 4 long plumose setae.

Etymology.

The name lancifera is derived from the Latin lancea, meaning “ spear ” or “ lance ”, and - fera (from ferre), meaning “ bearing ” or “ carrying ”. The name refers to the spear-like shape of the mandibles that resemble weapons borne by the gnathiid.

Remarks.

Gnathia lancifera sp. nov. can be recognised by the slightly produced frontal margin; a weakly rounded mediofrontal process; two strong, conical superior frontolateral processes; rounded and pronounced supraocular lobes; crescent-shaped mandibles that are strongly curved distally and dentate; and a pereonite 5 that is divided by a triangular pereonite 6.

As with G. spongicola and G. brevicula sp. nov., G. lancifera sp. nov. shares the uncommon feature of pereonite 5 being divided by pereonite 6. However, it can be distinguished by several key characteristics: it has significantly larger, crescent-shaped mandibles; a more prominently produced frontal margin; and relatively smaller eyes in proportion to the cephalosome. Additionally, the cephalosome of G. lancifera sp. nov. is densely covered with small tubercles, in contrast to the tubercle distribution in G. spongicola and G. brevicula sp. nov., where tubercles are mainly concentrated around the eyes and the posterior median region.