Birubius kinkus Barnard & Drummond 1978

Birubius kinkus

DESCRIPTION OF FEMALE.—Head about 20 percent of total body length, greatest width about 60 percent of length; rostrum almost unconstricted, broad, reaching apex of article 1 on antenna 1. Eyes medium, largely occluded with pigment. Article 1 on peduncle of antenna 1 about 1.4 times as long as wide, about 2.2 times as wide as article 2, ventral margin with about 10 setules, weakly produced dorsal apex with 4 setules; article 2 about 0.7 times as long as article 1, with apicoventral cycle of 6 setae; primary flagellum with 13–15 articles, about 1.2 times as long as peduncle, bearing several short aesthetascs; accessory flagellum with 10–12 articles. Spine formula on article 4 of antenna 2 = 1–3–4–4, dorsal margin with notch bearing 3 setae, ventral margin with 4 groups of 2 long to medium setae, one ventrodistal long spine; article 5 about 0.7 times as long as article 4, facial spine formula = 1–2, dorsal margin naked, ventral margin with 2 sets of 2–3 long to short setae, 2 ventrodistal long to medium spines; flagellum about 1.8 times as long as articles 4–5 of peduncle combined, with 17 articles. Mandibles with medium palpar hump; right incisor with 3 teeth; left incisor with 3 teeth in 2 branches; right lacinia mobilis bifid, distal branch much shorter than proximal, broad, almost subbifid, proximal branch simple, pointed, with marginal denticles; left lacinia mobilis with 4 teeth; right rakers 8; left rakers 8 plus one rudimentary; molar in form of elongate plaque, each molar with 8 primarily long spines, one short very weak spine strongly disjunct, each molar with plume; palp article 1 short, article 2 with one medium inner apical seta and 3 other shorter inner setae, article 3 about 0.9 times as long as article 2, oblique apex with 6 spine-setae, basofacial formula = 1–2 or 1–3. Inner plate of maxilla 1 ordinary, bearing one long apical pluseta, one shorter similar apicomedial seta, 2 apicolateral much shorter setae; palp article 2 with 4 apical medial marginal spines and 4 submarginal setae. Plates of maxilla 2 extending subequally, outer as broad as inner, outer with 4–5 apicolateral setae, inner with one medial seta. Inner plate of maxilliped with one large thick apical spine, 3 apicofacial setae, 4 medial setae; outer plate with 7 medial and apical spines, 2–3 apicolateral setae; palp article 1 with apicolateral seta, article 2 with 2 groups of 1–2 apicolateral setae, medial margin of article 2 moderately setose, article 3 protuberant, with 5 facial setae, 2 lateral setae, nail of article 4 long-medium, with 2 accessory setules, first of these 0.66 as long as primary nail. Coxa 1 strongly expanded distally, anterior margin almost straight; main ventral setae of coxae 1–4 = (7–8)–(7–8)–7–0, posteriormost seta of coxae 1–3 slightly shortened; anterior and posterior margins of coxa 4 strongly divergent, posterior margin oblique, almost straight, posterodorsal corner rounded, posterodorsal margin short, ordinary, width-length ratio of coxa 4 = 16:17. Long posterior setae on article 2 of gnathopods 1–2 and pereopods 1–2 = 3–5–5–(5–6), long anteriors = 4–(6–7)–0–0, short anteriors = 4–5–7–6, no others. Gnathopods ordinary; width ratios of articles 5–6 on gnathopods 1–2 = 22:31 and 22:33, length ratios = 73:60 and 66:55; palmar humps ordinary, palms oblique; article 5 of gnathopod 1 elongate, ovate, posterior margin rounded–flat; article 5 of gnathopod 2 elongate, ovate, posterior margin rounded. Pereopods 1–2 similar; facial setae formula on article 4 = 3 and 3, on article 5 = 4 and 5; main spine of article 5 extending to M. 80–100 on article 6, article 5 with 3 and 2 proximoposterior spines; spine formula of article 6 = 3 + 5 or 4 + 5 plus middistal seta; acclivity on inner margin of dactyls of pereopods 1–2 weak but produced, emergent setule short, midfacial pluseta ordinary. Coxae 5–7 posteroventral setule formula = 2–4–3. Articles 4–5 of pereopods 3–4 of ordinary width, facial spine rows moderately developed, facial ridge formula on article 2 of pereopods 3–5 = 0–2–2; width ratios of articles 2, 4, 5, 6 of pereopod 3 = 45:47:43:18, of pereopod 4 = 73:45:34:15, of pereopod 5 = 91:26:20:10, length ratios of pereopod 3 = 78: 33:44:50, of pereopod 4 = 96:58:45:54, of pereopod 5 = 124:33:30:32; article 2 of pereopod 5 reaching middle of article 5, one ventral setule elongate; medial apex of article 6 not combed, bearing 5 vestigial digital processes. Posteroventral corner of epimeron 1 rounded, posterior margin almost straight, corner with setule, anteroventral margin with 5–7 short setae, posteroventral face with 2–3 medium setae; posteroventral corner of epimeron 2 rounded, strongly protuberant, guarded by setule sinus, posterior margin almost straight, undulant, facial setae = 6–8 crowded, posteriormost pair set vertically; posteroventral corner of epimeron 3 weakly protuberant, with setule sinus above and 2 below corner, with small tooth, posterior margin weakly sinuous, with 1–2 setule notches and 2 long setae, ventral margin naked, face with horizontal row of 3–4 setae; epimeron 3 with small setule on posterodorsal margin set in weak notch. Urosomite 1 naked ventrally, articulation line short, almost absent; urosomite 3 protuberant dorsally. Rami of uropods 1–2 with articulate enlarged apical nails, outer ramus of uropod 1 with 5–8 dorsal spines, inner with 1–2, outer ramus of uropod 2 with 3–4 dorsal spines, inner with one dorsomedial spine; peduncle of uropod 1 with 5–6 apicolateral spines and 1–2 basofacial setae; medially with 5 marginal setae and spines, apicalmost an enlarged spine; peduncle of uropod 2 with 7–12 dorsal spines, medially with one small apical spine. Peduncle of uropod 3 with 6–7 ventral spines, dorsally with one lateral spine, one medial spine and setule; rami submasculine, inner extending to M. 85 on article 1 of outer ramus, apex with 2 setae, medial and lateral margins setose, article 2 of outer ramus short, 0.15, bearing 2 medium setae, medial margin of article 1 setose but not apically, lateral margin with 4 acclivities, spine formula = 2–2–2–2–2, setal formula = 0–1–1–1–1. Telson long, length-width ratio = 15:13, not fully cleft, each apex of medium width, rounded, lateral acclivity deep, narrow, bearing long lateral setule, spine next medial of length equal to setule, midlateral setules diverse. Cuticle with ordinary bulbar setules of varying sizes closely mixed with pipes, setules bearing apical halo, surface bearing extremely fine striations in form of linear fingerprint pattern, emergent setules especially short.

OBSERVATIONS.—Illustrations mainly taken from juvenile “x,” 6.0 mm, noted below; eyes of adult female slightly enlarged as shown in illustration from holotype female “a”; uropod 3 of adults as in B. kokorus (25) but with differences noted in description above.

Juvenile “x,” 6.0 mm, WPBES 51S/1: Eyes clear; head shorter than in adult; disjunct spine on left molar broken off (socket present), apparently absent on right molar; article 5 of pereopods 1–2 with 2 or 1 proximoposterior spines; main spine distally longer than in adult; article 5 on pereopod 4 slightly shorter than in adult; uropod 1 with only one basofacial seta (not shown on illustration).

Juvenile “y,” 5.8 mm: Uropod 1 lacking basofacial seta.

ILLUSTRATIONS.—Eye on lateral view of head slightly shortened dorsoventrally because of ocular shrinkage (inward pulling of eyes); maxilla 1 like that of B. maamus (21), inner plate with 2 small, one medium, one large seta, outer plate with one thickened spine, palp with 4 spines and 4 setae; maxilla 2 like that of B. jirrandus (30) but lobes slightly broader and inner plate with only one medial seta; maxilliped like that of B. kokorus (25) but main spine on inner plate illustrated, outer plate with 2 lateral setae, face of palp article 3 with 4 setae in tandem, article 3 produced as in B. kokorus, lateral margin of article 3 with one seta, palp article 4 illustrated; coxae 1–3 ordinary, as in B. kokorus.

HOLOTYPE.—NMV, female “a,” 6.84 mm.

TYPE-LOCALITY.—CPBS 51 S (resampled), 16 Feb 1972, Western Port, Victoria, Australia, 15.1 m, coarse sand, anchor in clay.

VOUCHER MATERIAL.—CPBS 51 S/1 (sample prior to 16 Feb 1972): juvenile “x,” 6.00 mm (illus.); juvenile “y,” 5.80 mm (illus.).

RELATIONSHIP.—Birubius kinkus differs from B. gambodeni (20) in the presence of strong posteroproximal spines on article 5 of pereopods 1–2 and in the elongation of article 5 on gnathopods 1–2. From B. maamus (21) to B. kyeemus (23), this species differs in the absence of one or more ventral setae on epimeron 3. From B. kokorus (25) B. kinkus differs in the presence of 2–3 posteroventral setae on epimeron 1 while having fewer setae on epimeron 3, in the more elongate article 5 of the gnathopods, and in the presence of only one spine on the iner ramus of uropod 1.

This species is placed in both keys, A and B. It is placed in Key A because the distal branch of the right lacinia mobilis is like that of B. gambodeni in being slightly thickened if not weakly subbifid.

MATERIAL.—CPBS, 4 samples from one station (9).

DISTRIBUTION.—Victoria, Western Port, 15 m, coarse sand on clay.