Agononida vanuacerta Poore & Andreakis, 2014, n. sp.

Agononida vanuacerta n. sp.

(Fig. 11)

Material examined. Holotype. VANUATU, W of Erromango I.: 18°48'S, 168°56'E, 641–649 m (MUSORSTOM 8 stn CP994), MNHN IU- 2010-6121* (supermale, 25 mm).

Paratype. Between Erromango and Tanna: 19°14'S, 169°20'E, 650–669 m (MUSORSTOM 8 stn DW989), MNHN IU- 2010-6118* (male, 12 mm).

Diagnosis. Telson anterolateral margin sinusoidal, smooth over anterior 60%, coarsely denticulate over convex remainder; no or short notch-like discontinuity between; elevated sharp submarginal ridge in mid-third, lower margin rounded. Pereopod 2–4 dactyli 6 times as long as basal width; robust setae on flexor margin of pereopod 2 number 14–20 (median 17); of pereopod 3, 3–5 (median 4); and of pereopod 4, 1. Pereopod 4 merus with 0–4 spines on upper face.

Description. Holotype, supermale, 25 mm. Carapace 0.93 times as long as greatest width. Gastric region with pair of small epigastric spines. Frontal margin inclined posteriorly at 15° from midline. Rostrum spiniform, 0.42 length of carapace (both measured from base of supraocular spines); supraocular spine 0.55 length of rostrum (both measured from base of rostrum). Thoracic sternite 3 0.48 width of sternite 4; midlength of sternal plastron (sternites 4–7) 0.55 width of sternite 7.

c d e Telson 1.8 times as wide as long; anterolateral margin sinusoidal, smooth over anterior 60%, coarsely denticulate over convex remainder; no or short notch-like discontinuity between; elevated sharp submarginal ridge in mid-third, lower margin rounded.

Eye with maximum corneal diameter 0.8 basal width of supraocular spines. Maxilliped 3 ischium 0.6 times as long as merus.

Pereopod 1 (cheliped) 3.8 times as long as carapace, merus 1.35 times as long as carapace, carpus 0.5 times as long as merus, propodus 1.3 times as long as merus, fingers 0.5 times as long as total propodus length. Merus with 1+7 spines along upper margin, 1+4 spines along mesial face, 1+15 spines along lateral face, 1+3 spines on lower margin; carpus with 1+2 spines on upper margin, 1+2 spines on mesial face, 1+2 spines on lateral face; propodus squarish oval in cross-section, with 4 spines on upper margin, with 1+3 spines along mesial face, with 1+1 spines on lateral face, with 2 spines on lower margin; dactylus cutting edge with ridge of c. 50 uneven teeth, few more prominent than others.

Pereopod 2 3.8 times carapace length, merus 1.2 times carapace length, 8 times a long as greatest width, carpus 0.25 times as long as merus, propodus 0.5 times as long as merus, dactylus 0.6 times as long as propodus; merus with 1+10 spines along extensor margin, with 1+9 spines along flexor margin; carpus with 1+3 spines along extensor margin; dactylus sinusoidal on extensor margin, tapering over distal half, 6.0 times as long as greatest basal width, with row of 20 robust setae distal to heel of flexor margin.

Pereopod 3 3.0 times carapace length, merus 1.2 times carapace length, 7.4 times a long as greatest width, carpus 0.25 times as long as merus, propodus 0.6 times as long as merus, dactylus 0.6 times as long as propodus; merus with 1+12 spines along extensor margin, with 1+9 spines along flexor margin; carpus with 1+4 spines along extensor margin; dactylus sinusoidal on extensor margin, tapering evenly, 6 times as long as greatest basal width, with row of 5 robust setae distal to heel of flexor margin.

Pereopod 4 3.0 times carapace length, merus 1.0 times carapace length, 5.6 times a long as greatest width, carpus 0.25 times as long as merus, propodus 0.6 times as long as merus, dactylus 0.5 times as long as propodus; merus with 1+14 spines along extensor margin, with 1+11 spines along flexor margin, with 1 and 4 spines on upper face; carpus with 1+3 spines along extensor margin; dactylus 6 times as long as greatest basal width, with 1 robust seta distal to heel of flexor margin.

Paratype, male, 12 mm, MNHN IU-2010-6118. Pereopod 1 (cheliped) 4.2 times as long as carapace, merus 1.3 times as long as carapace, carpus 0.5 times as long as merus, propodus 1.4 times as long as merus, fingers 0.5 times as long as total propodus length. Pereopod 1 merus with 1+5 spines along upper margin, 1+3 spines along mesial face, 1+12 spines along lateral face, 1+2 spines on lower margin; carpus with 1+2 spines on upper margin, 1+2 spines on mesial face, 1+0 spines on lateral face; propodus oval in cross-section, with 4 spines on upper margin, with 1+1 spines along mesial face, with 1+0 spines on lateral face, with 1 spine on lower margin.

Pereopod 2 3.5 times carapace length, merus 1.3 times carapace length, 8 times a long as greatest width, carpus 0.25 times as long as merus, propodus 0.6 times as long as merus, dactylus 0.6 times as long as propodus; merus with 1+12 spines along extensor margin, with 1+7 spines along flexor margin; carpus with 1+1 spines along extensor margin; dactylus sinusoidal on extensor margin, tapering over distal half, 6.0 times as long as greatest basal width, with row of 14 robust setae distal to heel of flexor margin.

Pereopod 3 3.5 times carapace length, merus 1.2 times carapace length, 8 times a long as greatest width, carpus 0.25 times as long as merus, propodus 0.7 times as long as merus, dactylus 0.6 times as long as propodus; merus with 1+12 spines along extensor margin, with 1+7 spines along flexor margin; carpus with 1+1 spines along extensor margin; dactylus sinusoidal on extensor margin, tapering evenly, 6 times as long as greatest basal width, with row of 3 or 5 robust setae distal to heel of flexor margin.

Pereopod 4 3.2 times carapace length, merus 1.1 times carapace length, 6.5 times a long as greatest width, carpus 0.25 times as long as merus, propodus 0.8 times as long as merus, dactylus 0.6 times as long as propodus; merus with 1+12 spines along extensor margin, with 1+7 spines along flexor margin, without spines on upper face; carpus with 1+2 spines along extensor margin; dactylus 6 times as long as greatest basal width, with 1 robust seta distal to heel of flexor margin.

Variation. The supermale holotype has 20, 4 or 5 and 1 robust setae on pereopods 2–4 respectively while the smaller male has 14, 3 or 5 and 1 spines respectively. The merus of pereopod 4 of the holotype has one facial spine on one side and 4 on the other; the smaller male has none.

Colour. Unknown.

Etymology. From Vanuatu, type locality and incerta, original species in this complex.

Distribution. Vanuatu, 15°S–19°S, 641–699 m (median 653 m) depth.

Remarks. Molecular analysis alerted us to the existence of this new taxon in the A. incerta species complex. Agononida vanuacerta was found sympatric in Vanuatu with A. norfocerta (from clade B) from which it differs in having a sharp step between the anterior and posterior section of the anterolateral margin of the telson, and possessing spines on the upper face of pereopod 4 (at least in the adult). The numbers of robust setae on the dactyli of pereopods 2–4 overlap. The species is sister to A. indocerta within clade A.

Agononida vanuacerta n. sp., based on only two individuals, is almost indistinguishable from A. africerta. The holotype is a supermale, at 25 mm smaller than a supermale of A. africerta (MNHN IU-2008-10192) at 31 mm. The numbers of robust setae on the pereopodal dactyli of the two species overlap. The anterolateral margin of the telson of the supermale of A. vanuacerta appears more complexly denticulate than that of A. africerta (cf. Figs 3 a–d, 11a but difficult to quantify from one example). This feature in the smaller male is straighter overall than in small males and females of A. africerta. The lateral face of the merus of pereopod 1 and extensor margins of pereopods 2–4 of smaller males and females have around 12 spines in A. vanuacerta and always more, 15–19, in A. africerta.