Rhepoxynius abronius (J. L. Barnard 1960)

Rhepoxynius abronius (J.L. Barnard)

Paraphoxus abronius J.L. Barnard, 1960:203–205, pl. 5; 1966a:88

DESCRIPTION OF FEMALE (female “p,” 3.11 mm).—Head about 20 percent of total body length, greatest width about 75 percent of length, rostrum constricted, narrow, almost reaching middle of article 2 on antenna 1. Eyes medium, largely occluded with pigment, ommatidia ordinary. Article 1 of peduncle on antenna 1 about 1.2 times as long as wide, about twice as wide as article 2, ventral margin with about 7 setules, weakly produced dorsal apex with 2 setules-setae, article 2 about 0.65 times as long as article 1, with ventral row near apex of 5 setae, primary flagellum with 7 articles, about 0.6 times as long as peduncle, bearing 1 each short aesthetasc on articles 3–6; accessory flagellum with 6 articles. Antenna 2 sharply ensiform as in variatus; article 3 with dorsal spine; spine formula of article 4 = 3–3–3, dorsal margin with weak notch bearing 3 setae, ventral margin with 9 groups of 1–2 long to medium setae, 1 ventrodistal long spine, article 5 about 0.65 times as long as article 4, facial spine formula = 2, dorsal margin bearing 2 sets of thin setae, ventral margin with 4 sets of 1–2 long to short setae, 3 ventrodistal long to medium spines, 1 spine set facially; flagellum about 0.85 times as long as articles 4–5 of peduncle combined, with 8 articles.

Epistomal cusp huge, blunt. Mandibles with weak palpar hump, right incisor with 3 teeth, third about in middle, left incisor with 3 humps in 2 branches; right lacinia mobilis thick, bifid, both branches blunt, left lacinia mobilis with 5 teeth, middle teeth shortened; right rakers 8 plus 1 rudimentary, left rakers 8 plus 2 rudimentaries; molars composed of short, bulbous protrusions, right molar with 6 primarily long spines plus thin seta weakly disjunct, left molar with 7 primarily long spines, plus 1 thin seta weakly disjunct, molar without plume; palp article 1 short, article with 1 short inner apical seta and 1 other short inner seta, article 3 about as long as article 2, oblique apex with 11 spine-setae, basofacial formula = 0–2. Inner plate of maxilla 1 ordinary, bearing 1 medium apical pluseta, no apicomedial seta, 2 apicolateral much shorter setae, palp article 2 with 1 apical spine, 1 apicolateral, 5 medial, and 5 submarginal setae. Plates of maxilla 2 extending equally, outer much broader than inner, outer with 1 apicolateral seta, inner with 1 medial seta. Inner plate of maxilliped with 1 large thick apical spine, 2 apicofacial setae, 4 medial setae, outer plate with 5 medial spines, no apicolateral setae or cusp, palp article 1 with 1 apicolateral seta, article 2 with 2 groups of 3 apicolateral setae, medial margin of article 2 moderately setose, article 3 with 13 scattered facial setae, 2 lateral setae, nail of article 4 short, almost fused, with 2 accessory setules.

Coxa 1 scarcely expanded apically, anterior margin straight, main ventral setae of coxae 1–4 = 5–9–8–1; posteriormost seta of coxae 2–3 slightly shortened; anterior and posterior margins of coxa 4 weakly divergent, posterior margin weakly convex, posterodorsal corner rounded, posterodorsal margin short to ordinary, weakly concave, width-length ratio of coxa 4 = 15:13.

Gnathopods generally ordinary but hands weakly mitelliform and palms almost transverse, width ratios on articles 5–6 of gnathopods 1–2 = 30:30 and 30:30, length ratios = 65:45 and 55:42, palmar humps very small, palms transverse, article 5 of gnathopod 1 elongate, ovate, posterior margin rounded, article 5 of gnathopod 2 elongate, ovate, posterior margin rounded, almost lobate. Pereopods 3–4 similar, facial setae formula on article 4 = 7 and 7, on article 5 = 7 and 5, main spine of article 5 extending to M. 90 on article 6, article 5 with 1 small proximoposterior spine on pereopod 4 only, spine formula of article 6 = 5 + 7 and 5 + 7 plus no middistal seta, some spines especially long, acclivity on inner margin of dactyls of pereopods 3–4 sharp, produced as tooth, emergent setule short, midfacial pluseta ordinary. Coxae 5–7 posteroventral seta formula = 2–12–2; articles 4–5 of pereopods 5–6 broad, facial spine rows moderately developed, spines thin, facial ridge formula of article 2 on pereopods 5–7 = 0–1–1; width ratios of articles 2, 4, 5, 6 of pereopod 5 = 57:51:46:20, of pereopod 6 = 87:44:34:14, of pereopod 7 = 103:27:24:12; length ratios of pereopod 5 = 94:41:48:43, of pereopod 6 = 103:75:46:50, of pereopod 7 = 100:25:31:31; article 2 of pereopod 7 reaching middle of article 4, posterior margin with 7 large serrations, medial and lateral apices of article 6 very finely combed, lacking digital processes.

Posteroventral corner of epimeron 1 rounded, posterior margin weakly convex, naked, anteroventral margin with 5 long to medium setae, posteroventral face with 3 long setae set vertically. Posteroventral corner of epimeron 2 rounded, posterior margin weakly convex, naked, facial setae = 10, posterior triad set vertically. Posteroventral corner of epimeron 3 quadrate, weakly protuberant, posterior margin weakly convex, with 3 setae near corner, above with 1 setule notch, ventral margin with 4 setae mainly posterior.

Urosomite 1 with lateral setule at base of uropod 1, articulation line only partly complete, urosomite 3 unprotuberant dorsally. Rami of uropods 1–2 with articulate but tightly fixed apical nails, outer ramus of uropod 1 with 4 widely spread dorsal spines, inner with 2, outer ramus of uropod 2 with 2 dorsal spines, inner with 1 dorsomedial spine. Peduncle of uropod 1 with no basofacial setae, 4 apicolateral thin spines (basalmost = short seta), medially with 6 marginal setae and spines, apicalmost a thin spine, no displaced spine. Peduncle of uropod 2 with 6 long and thin dorsal spines, medially with 1 medium apical spine; apicolateral corners of peduncles on uropods 1–2 without comb. Peduncle of uropod 3 with 3–4 ventral spines, dorsally with 1–2 lateral spines, 1 medial setule, rami submasculine, inner extending to M. 100 on article 1 of outer ramus, apex with 2 long setae, medial margin with 1 seta, article 2 of outer ramus ordinary, 0.18, bearing 2 long setae, medial margin of article 1 with 3 setae, lateral margin with 2 acclivities, spine formula = 1–1–1, setal formula = 1–1–1. Telson especially long, length-width ratio = 18:11, almost fully cleft, each apex narrow, pointed (but not as extended as in R. variatus), lateral acclivity broad, shallow, bearing ordinary lateral setule, 2 spines next medial longer (or second shorter) than setule, midlateral setules diverse, larger medium in size.

DESCRIPTION OF MALE (male “m,” 2.77 mm).—Rostrum like female. Article 1 of antenna 1 and articles 3–4 of antenna 2 with medial pubescence; article 2 of antenna 1 with 7 ventral setae evenly spread, not skewed apically, primary flagellum elongate, with 8 articles, 1 calceolus each on articles 2–5, aesthetascs weakly developed, accessory flagellum shortened, 5–articulate. Facial spine formula on article 4 of antenna 2 = 3–3–2, article 5 with 3 dorsal sets of male setae and no calceoli, ventrodistal apex with 2 thin spines and 1 setule, calceolus formula on flagellum = 2, 3, 4, 6, 8…n. Basofacial setal formula of article 3 on mandibular palp = 0–2, right lacinia mobilis bifid, distal branch shortened.

Article 5 of pereopods 3–4 with 1 posteroproximal small spine. Article 2 of pereopod 7 narrower than in female, article 5 with 2 special posterodistal male spines. Epimera 1 and 3 but not 2, broadened, posterior margin of epimeron 3 shortened and very convex, setal formulas, epimeron 1 anteroventral = 3, posteroventral = 3; epimeron 2 facial = 12 (posterior triad vertical), epimeron 3 posterior = 2, ventral = 5 (widely spread). Spine formulas of uropods: uropod 1 peduncle apicolateral = 3, basofacial = 1, uropod 2 peduncle dorsal = 6, dorsal spines on outer ramus of uropod 1 = 3, of uropod 2 = 2, inner ramus of uropod 1 = 2, of uropod 2 = 1, spine formula on article 1 of outer ramus on uropod 3 = 0–0–0–0–0–1, short setal formula = 0–0–1–1–1–1, long setae = 1–1–1–1–1–1. Telson like female but with 1 row of denticles on each lobe, distal spines scarcely shortened.

MATERIAL.—AHF Velero IV 5180, southern California, 20 m, male “m,” 2.77 mm, female “p,” 3.11 mm. USNM Acc. 125734, no. 9, off Corona del Mar, California, near bell buoy, 7 fms, 17 May 1933, coll. G.E. MacGinitie, 2 specimens.

RELATIONSHIP.—Differing from R. variatus in the vertical placement of the posterior facial setae on epimeron 2, the broader hands of the gnathopods, and the generally smaller and more numerous (5+) serrations on article 2 of pereopod 7. Minor and more unwieldy characters of R. abronius are the more equally bifid right lacinia mobilis, more strongly spinose uropod 1 (3 spines dorsolaterally on peduncle, more than 1 spine on outer ramus), the presence of more than 2 apical elements on each telsonic lobe, and the denser facial spination on articles 4–5 of antenna 2 (at least 3 sets of spines on article 4, at least 2 spines total on article 5). This is the final species to have any semblance of a fully displaced spine on the molar; the element present on the specimen in this reanalysis is very thin and wire-like.

DISTRIBUTION.—California, 9–274 m.