Rhepoxynius stenodes (J. L. Barnard 1960)

Rhepoxynius stenodes (J.L. Barnard)

Paraphoxus stenodes J.L. Barnard, 1960:221–224, pls. 17, 18; 1964b:244, 245; 1966a:89; 1969:198.—Reish and Barnard, 1967:19.

DESCRIPTION OF FEMALE (female “t,” 3.39 mm).—Head about 21 percent of total body length, greatest width about 75 percent of length, rostrum constricted, narrow, elongate, slightly exceeding apex of article 1 on antenna 1. Eyes small to medium, stained mahogony, ommatidia ordinary. Article 1 of peduncle on antenna 1 about 1.5 times as long as wide, about twice as wide as article 2, ventral margin with about 4 setules, weakly produced dorsal apex with 2 setules and seta, article 2 about 0.7 times as long as article 1, with ventral cycle of 9 widely spread setae, primary flagellum with 6 articles, about 0.45 times as long as peduncle, bearing several short aesthetascs in formula of 0–0–1–1–1–0; accessory flagellum with 6 articles. Antenna 2 poorly ensiform; spine formula of article 4 = 3–3–3, dorsal margin with notch bearing 3 setae, ventral margin with 6 groups of 1 each long setae, 5 ventrodistal long setae and long facial spine, article 5 about 0.75 times as long as article 4, facial spine formulae = 1, dorsal margin naked, bearing pair of setules, ventral margin with 4 sets of 1–2 long to short setae, 3 ventrodistal long setae, 1 subdistal thin facial spine; flagellum about 0.85 times as long as articles 4–5 of peduncle combined, with 7 articles.

Epistome unproduced. Mandibles with weak palpar hump, right incisor with 3 teeth, left incisor with 3 humps in 2 branches, right lacinia mobilis bifid, distal branch shorter than proximal, proximal branch simple, left lacinia mobilis with 1 main tooth at side plus 5 accessory vestigial teeth, latter tooth area shortened; right rakers 9, left rakers 11; molars composed of short bulbous humps, right molar with 5 primarily short to medium spines plus 1 short spine weakly disjunct, left molar with 5 short to medium spines, no spine disjunct, no molar with plume; palp article 1 short, article 2 with 1 short inner apical seta and 1 other short inner seta, article 3 about as long as article 2, oblique apex with 13 spine-setae, basofacial formula = 0–1. Each outer lobe of lower lip with 1 weak cone. Inner plate of maxilla 1 thin, bearing 1 medium apical pluseta, 1 similar apicomedial seta, 2 apicolateral much shorter setae, palp article 2 with 1 apical spine, 1 apicolateral seta and 2 apical medial marginal setae and 5 submarginal setae. Inner plate of maxilla 2 shorter than outer, outer broader than inner, outer with 2 apicolateral setae, inner with 1 medial seta. Inner plate of maxilliped with 1 thick short apical spine, 2 apicofacial setae, 4 medial setae, outer plate with 7+ medial and apical spines, no apicolateral setae, no cusp, palp article 1 with 1 apicolateral seta, article 2 with 2 groups of 2–3 apicolateral setae, medial margin of article 2 strongly setose, article 3 with 5 facial setae, 3–5 lateral setae, nail of article 4 short, scarcely distinct, with 2 accessory setules.

Coxa 1 scarcely expanded apically, anterior margin convex, main ventral setae of coxae 1–4 = 7–9–9–7, posteriormost seta of coxae 1–4 longest; anterior and posterior margins of coxa 4 weakly divergent, posterior margin not very oblique, weakly convex, posterodorsal corner sharp, posterodorsal margin short, concave, width-length ratio of coxa 4 = 3:4.

Gnathopods generally ordinary, hands somewhat thin, width ratios on articles 5–6 of gnathopods 1–2 = 33:32 and 30:31, length ratios = 65:48 and 56:48, palmar humps ordinary, palms weakly oblique, article 5 of gnathopod 1 elongate, ovate, posterior margin rounded, short, article 5 of gnathopod 2 elongate, ovate, posterior margin rounded, short, weakly produced.

Pereopods 3–4 similar, facial setae formula on article 4 = 7 and 9, row closely parallel to apex, not axial, on article 5 = 7 and 5, main spine of article 5 extending to M. 90 on article 6, article 5 with 1, weakly 2 proximoposterior spines, spine formula of article 6 = 5 + 7 and 5 + 8 and no middistal seta, some spines especially long, acclivity on inner margin of dactyls of pereopods 3–4 obsolescent, emergent setule short, midfacial pluseta ordinary. Coxae 5–7 posteroventral seta formula = 2(none posterior)-7 (none posterior)-1. Articles 4–5 of pereopods 5–6 of ordinary width, facial spine rows sparse to moderately developed, facial ridge formula of article 2 on pereopods 5–7 = 0–1–1; width ratios of articles 2, 4, 5, 6 of pereopod 5 = 54:46 :41:17, of pereopod 6 = 70:45:32:14, of pereopod 7 = 85:24:23:10; length ratios of pereopod 5 = 90:40:40:30, of pereopod 6 = 92:65:39:45, of pereopod 7 = 100:23:25:27; article 2 of pereopod 7 reaching apex of article 4, with 7–8 medium teeth on posterior margin, medial apex of article 6 strongly combed, straight.

Posteroventral corner of epimeron 1 rounded, posterior margin convex, corner without setule, anteroventral margin with 6–7 medium setae, posteroventral face with 3 long setae set obliquely. Posteroventral corner of epimeron 2 rounded, not guarded by setule sinus, posterior margin convex, facial setae = 11, posterior triad set somewhat vertically. Posteroventral corner of epimeron 3 weakly protuberant, with 1 seta, posterior margin weakly convex, with 1 setule notch, ventral margin with 6 setae mainly posterior but almost evenly spread, face naked; epimera 1–3 lacking large seta on posterodorsal margin.

Urosomite 1 with lateral setule at base of uropod 1, articulation line almost complete, urosomite 3 unprotuberant dorsally. Rami of uropods 1–2 with fused apical nails, outer ramus of uropod 1 with 1 dorsal spine near base, inner with 1, outer ramus of uropod 2 with 1 dorsal spine near base, inner with 1 dorsomedial spine. Peduncle of uropod 1 with 2–3 basofacial setae and 1 medium apicolateral spine, plus smaller marginal seta, medially with 3 marginal setae and spines, apicalmost an ordinary spine, others = setae. Peduncle of uropod 2 with 2 apical dorsal spines in tandem and 4 setae towards base, medially with 1 large apical spine; apicolateral corners of peduncles on uropods 1–2 without comb. Peduncle of uropod 3 with 3 ventral spines, dorsally with lateral spine and medial setule, rami feminine, inner extending to M. 95 on article 1 of outer ramus, apex with 1 seta, medial margin with 1 seta, article 2 of outer ramus short, 0.17, bearing 2 long setae, apicomedial margin of article 1 with 1 seta, lateral margin with 2 acclivities, spine formula = 0, setal formula = 1–1–2. Telson especially long, length-width ratio = 8:5, almost fully cleft, each apex narrow, rounded, lateral acclivity shallow, with lateral and medial elongate seta separated by medium setule or with 2 lateral setae, setule and medial seta, midlateral setules medium, equal or diverse (variable).

MATERIAL.—AHF Velero IV 5111–57, southern California, female “t,” 3.39 mm, female “u,” 3.33 mm (both illus.).

RELATIONSHIP.—This species is the plesiomorphic member of the flock of Rhepoxynius characterized by rounded anterior face of the epistome; it is the only member with normal, nonrhombic or nonjeweled spines on uropods 1–2. In addition it differs from R. daboius just ahead of it in gradational morphology, in the more numerous dorsal spines on the peduncle of uropod 2, in the more numerous medial spines on the peduncle of uropod 1, and in the weakly disjunct, ordinary (not wire-like) spine on the molar. Hence, stenodes, though lacking epistomal cusp, is more plesiomorphic in the other characters mentioned than is R. dabious. One would suspect, therefore, that R. dabious could not be the ancestor of stenodes, because R. dabious lacks the slightly disjunct molarial spine and has lost important spines on uropods 1–2.

DISTRIBUTION.—California from Morro Bay to Baja California at Bahía de San Cristobal, 2–374 m.