Comprehensive Description
provided by Smithsonian Contributions to Zoology
Birubius kabbulinus
DESCRIPTION OF MALE.—Head (broken) about 21 + percent of total body length, greatest width about 55 (estimated) percent of length; rostrum constricted, narrow, elongate, probably reaching middle of article 2 on antenna 1. Eyes large, clear of pigment but stained deep burgundy, ommatidia especially large. Article 1 on peduncle of antenna 1 about 1.2 times as long as wide, about twice as wide as article 2, ventral margin with about 10 setules, produced dorsal apex with one setule; article 2 about 0.8 times as long as article 1, with ventral cycle of 4 setae; primary flagellum with 10 articles, about 1.1 times as long as peduncle, lacking aesthetascs; accessory flagellum with 7 articles. Spine formula on article 4 of antenna 2 = 3–4–3, dorsomedial margin of articles 3–4 fuzzy, ventral margin with 4 groups of 1–3 medium setae, one ventrodistal medium spine; article 5 about 0.9 times as long as article 4, facial spine formula = 2. dorsal margin bearing 3 sets of male setae and one calceolus, ventral margin with 2 sets of 2 medium to short setae, 2 thin ventrodistal medium spines; flagellum elongate, flagellar formula = (26–29), 2, 4, 6…20 or 2, 4, 6…26. Mandibles with medium palpar hump; right incisor with 3 teeth: left incisor with 4 humps in 2 branches; right lacinia mobilis simple, denticulate; left lacinia mobilis with 5 teeth; right rakers 5; left rakers 8; molar in form of bulbous hump demarcated mainly by spines, each molar with 4 primarily long spines, none disjunct, each molar with plume; palp article 1 slightly elongate, article 2 with one long inner apical seta and 2 other shorter inner setae, article 3 about 0.9 times as long as article 2, oblique apex with 6 spine-setae, basofacial formula = 1–1. 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 2 apicalmedial marginal spines and 3 submarginal setae. Plates of maxilla 2 extending equally, of equal width, outer with 2 apicolateral setae, inner with one medial seta; [maxillipeds missing]; coxa 1 strongly expanded distally, anterior margin weakly concave; main ventral setae of coxae 1–4 = 3–4–4–0, posteriormost seta of coxae 1–3 longest; anterior and posterior margins of coxa 4 almost parallel, posterior margin convex, posterodorsal corner rounded, posterodorsal margin short, concave, undulant, width–length ratio of coxa 4 = 14:15. Long posterior setae on article 2 of gnathopods 1–2 and pereopods 1–2 = 1–1–2–2, long anteriors = 2–5–0–0, short anteriors = 1–1–1–1, no others. Gnathopods ordinary; width ratios of articles 5–6 on gnathopods 1–2 = 24:36 and 26:37, length ratios = 56:60 and 49:59; palmar humps ordinary, palms oblique; article 5 of gnathopod 1 ovate, posterior margin rounded; article 5 of gnathopod 2 ovate, posterior margin rounded, almost lobate. Pereopods 1–2 similar; facial setae formula on article 4 = 2 and 2, on article 5 = 3 and 2; main spine of article 5 extending to M. 85 on article 6, article 5 with one proximoposterior spine; spine formula of article 6 = 3 + 3, lacking middistal seta, one spine especially long; acclivity on inner margin of dactyls of pereopods 1–2 weak, emergent setule long, midfacial pluseta very short. Coxae 5–7 posteroventral setule formula = 1–1–1. 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 (see “Observations”); width ratios of articles 2, 4, 5, 6 of pereopod 3 = 39:37:30:12, of pereopod 4 = 54:37:23:10, of pereopod 5 = 73: 17:15:7, length ratios of pereopod 3 = 60:26: 30:36, of pereopod 4 = 77:47:35:49, of pereopod 5 = 106:26:23:23; article 2 of pereopod 5 exceeding apex of article 4; medial apex of article 6 combed, bearing 2 obsolescent digital processes. Posteroventral corner of epimeron 1 rounded, posterior margin deeply convex, anteroventral margin with 4–5 medium setae, posteroventral face with 3 medium setae; posteroventral corner of epimeron 2 rounded? (damaged), posterior margin strongly convex, facial setae = 6, posteriormost triad set vertically; posteroventral corner of epimeron 3 rounded, with setule sinus, posterior margin convex, with one setule notch, ventral margin with 5 setae evenly spread; epimera 1–2 with tiny setule on posterodorsal margin. Urosomite 1 naked, articulation line almost complete; urosomite 3 protuberant dorsally. Rami of uropods 1–2 with articulate enlarged apical nails, outer rami of uropods 1–2 and inner ramus of uropod 1 with one accessory setule, outer ramus of uropod 1 with 2 dorsal spines, inner with one, outer ramus of uropod 2 with 3 dorsal spines, inner with one dorsomedial spine; peduncle of uropod 1 with 3 apicolateral spines and one basofacial seta, medially with 5 marginal spines, apicalmost weakly enlarged; peduncle of uropod 2 with 7 dorsal spines, medially with one apical setule. Peduncle of uropod 3 with 5 ventral spines, dorsally with one lateral spine, one medial setule; rami masculine, inner extending to M. 100 on article 1 of outer ramus, apex with 2–3 setae, medial and lateral margins setose, article 2 of outer ramus elongate, 0.25, bearing 2 long setae, apicomedial margin of article 1 setose, lateral margin with 2 acclivities, spine formula = 1–1–1, setal formula = 1–1–1. Telson long, length–width ratio = 6:5, almost fully cleft, each apex narrow, rounded–truncate, lateral acclivity weak, bearing ordinary lateral setule, spine next medial shorter than setule, midlateral setules weakly diverse. Cuticle with ordinary but very sparse bulbar setules.
OBSERVATIONS.—Article 2 of pereopod 5 with 2 anterior ridges, one short and weak and possibly an artifact; upper lip and lower lip poorly observed, damaged during dissection; maxillipeds missing.
HOLOTYPE.—AM, male “a,” 3.19 mm. Unique.
TYPE-LOCALITY.—AM P.18125, 12 Dec 1939, Antechamber Bay, Kangaroo Island, South Australia, light in net at night.
RELATIONSHIP.—Like B. eake (32), this species lies just outside the B. taldeus (34) group. The right lacinia mobilis is simple, the rostrum narrow, and several rami of uropods 1–2 bear immersed apical setules, but unlike the B. taldeus group, B. eake and B. kabbulinus have more than 2 setae each on coxae 1–2 and bear ventral or ventrofacial setal-spines on epimeron 3. Birubus kabbulinus differs from B. eake in the fully ventral position of the setae on epimeron 3, bears an elongate article 2 on the outer ramus of uropod 3, and lacks the enlarged ventral spine on urosomite 1.
Birubius yorlunus (31) bears continuous dorsal spination on the rami of uropods 1–2 and fully facial setae on epimeron 3. Routine distinctions however, are complicated; see B. yorlunus for
