Skaptopus brychius Thomas & Barnard 1983

Skaptopus brychius

ETYMOLOGY—From the Greek brychios (deep).

DESCRIPTION OF MALE (holotype male “g,” 2.70 mm).—Head about 18 percent of total body length (including head), rostrum unconstricted apically, with rounded ventral lappet but no midsaggital keel or between-the-antennae process; dorsal cephalic pits rudimentary and arranged in 2 bilateral longitudinal rows. Eyes absent or possibly identifiable as weak capsule containing several angular ommatidial elements. Article 1 on peduncle of antenna 1 about 0.75 times as long as wide (including medial length as measurement standard), more than 1.4 times as wide as article 2, ventral margin with 4 setules, unproduced dorsal apex with 2 setules, lateral face naked; article 2 about half as long as article 1 (using medial length of article 1 again), apical margin with several setules, ventral margin naked; article 3 more than 0.75 times as long as article 1 (using medial lengths), enlarged relative to other platyischnopids, ventral margin naked, apical margins both laterally and medially with wide and dense row of long aesthetascs; primary flagellum almost 1.5 times as long as peduncle, with 5 articles, basalmost elongate, thickened, with sinuous posterior margin but lacking aesthetascs, formula of aesthetascs thus 0–L–L–L–s; accessory flagellum about 0.35 times as long as primary flagellum, with 2 thin articles. Dorsal (rectified) margin on article 4 of antenna 2 naked, ventral margin with 3 setules, outer face with spine and setule, outer apex with group of 4 setae; article 5 about 0.58 times as long as article 4, naked except for setules at apex; flagellum more than 0.80 times as long as articles 4–5 of peduncle combined, with 4 articles.

Mandibles thick, bulky, with small palpar hump, incisors of modified phoxocephalid form, thickened, each with outer callus, right incisor with 3 teeth of phoxocephalid form plus incision and cusp outside largest middle tooth, left incisor with 4 vestigial teeth in 2 branches plus inner slit, each lacinia mobilis flabellate and 4-toothed but right element irregular; raker spines absent; molar huge, weakly pubescent (“mohair” composition); length ratio of mandibular palp articles = 18:60:70, article 1 short, unarmed, article 2 elongate, bearing one midmedial seta, article 3 obliquely truncate, apex bearing 4 straight sharp spines.

Lower lip with fleshy inner lobes, with aboral raphus, oral side lacking structure, cones absent, pubescence ordinary.

Inner plate of maxilla 1 of ordinary subrectangular form, short, subtruncate, armed with one apical simple seta; outer plate with 7 ordinary spines either bifid or weakly serrate or simple; palp uniarticulate, very broad, short, with one apical pluseta. Inner plate or maxilla 2 much shorter and narrower than outer, apical spine-setae thick, stiff, sparse on inner plate, outer plate with pair of apicolateral spine-setae. Plates of maxilliped sparsely armed, inner small, outer large, inner with truncate apex bearing medial thick spine and 2 lateral spine-setae, outer with 4 medial and apical short thick spines in notches widely separate plus 2 ventrofacial thin spines; palp stout, article 2 with sparse medial setae, article 3 with 1 facial seta, dactyl subunguiform or unguiform, apical nail distinct, short, thick, dactyl not evenly tapered.

Lower margins of coxae 1–4 as attached to body forming even curve, no disjunctions, coxae progressively longer and broader, coxa 1 longer than broad, posteriorly naked, with 2 ventral setules; coxa 2 weakly curved and slightly attenuate anterodistally, with 2 posterofacial setae and 2 ventral setules; coxa 3 similar, with one posterofacial seta, 3 ventral setules; coxa 4 very large, broad, about 1.6 times as wide as long, posterior lobe very broad, rounded, ventral margin with 1 setule.

Gnathopods with relatively short (for the family) article 5, sixth articles weakly chelate, not tapering, weakly elongate, axial margins not biconvex, length ratios of articles 5 and 6 on gnathopods 1–2 = 105:96 and 152:108; palmar humps small and sharp, no flake; article 3 short; posterior margin of article 2 with 0 and 1 seta respectively on gnathopods 1–2.

Pereopod 4 like pereopod 3, main apical spine of article 5 extending to about M. 90 on article 6; spine formula on article 6 of both pairs = 3 + 2 + 0, third member of lateral set not strongly disjunct, dactyls with poorly developed nail demarcation apically.

Articles 4–5 of pereopods 5–7 narrow; facial spine rows sparse to absent; facial ridge formula on article 2 of pereopods 5–7 = 0–0–1 (part); width ratios of articles 2, 4, 5, and 6 on pereopod 5 = 23:21:16:8, on pereopod 6 = 67:27:18:8, on pereopod 7 = 73:43:26:15, length ratios on pereopod 5 = 63:37:40:37, on pereopod 6 = 70:51:42:41, on pereopod 7 = 101:68:58:65, article 2 of pereopod 5 narrow basally, scarcely widening distally, with weak posteroventral lobe; of pereopod 6 orbicular, with adz-shaped posteroventral lobe; of pereopod 7 broad, galeate, with 6 posterior serrations, however, ventralmost notch slightly enlarged, posteroventral lobe very large, broad, subtruncate; dactyls medium, thin, pointed.

Epimeron 1 broadly rounded posteriorly but with tiny sharp posteroventral tooth, midventral margin with notch and setal socket (this apparent seta worn off of hundreds of specimens); epimeron 2 dominant, posterior margin sinuous and sweeping into large, sharp, attenuate tooth, ventral margin with 3 widely spaced short spine-setae, epimeron 3 similar but scarcely less dominant, tooth weakly shorter, ventral margin naked; each side of main dorsal tooth margin of pleonites 1–2 with one small accessory tooth, pleonite 3 with 2 large teeth on each side besides middorsal tooth.

Urosome tall, thick (but thin side to side from dorsal view), smooth dorsally, urosomite 2 extremely short, urosomite 1 with large ventral spine near base of uropod 1, latter well exceeding uropod 2, uropod 3 extremely elongate. Peduncle of uropod 1 with one lateral facial spine, one middorsolateral spine, lateral apex with sharp cusp and 2 straight diverse spines, medial apex also with cusp and pair of spines, medial margin with one spine, inner ramus longer than peduncle, outer shorter than inner, outer with one dorsal spine, inner with 2, each ramus with 4 apical diverse spines on oblique sloping margin. Dorsolateral and dorsomedial apices of peduncle on uropod 2 each with spine, lateral also with sharp cusp, inner ramus longer than peduncle, outer shorter than inner, outer ramus lacking dorsal spine, inner with 2 spines, apices like uropod 1.

Peduncle of uropod 3 short, with midfaciolateral spine, one apicolateral and one apicomedial spine, 3 apicoventral spines in group, inner ramus small, scale-like, with one medial and one apical setule; outer ramus very elongate, article 2 about 0.37 times as long as article 1, lateral margins of article 1 with spine formula of 2–2–2–2, of article 2 = 0, setal formula of medial margin of article 1 = 1–0–0–0, of article 2 = 0, medial spine formula of article 1 = 2–2–2–2, of article 2 = 0, article 2 with 3 apical setules in alternate fashion.

Telson about 1.5 times as long as wide, cleft about 2/3 of length, gape narrow, each lobe with sharp apex armed with setule, then sharp subapical medial acclivity bearing one spine, then fully dorsomedial acclivity along cleft bearing spine with dorsolateral setule pairs at M. 60.

DESCRIPTION OF FEMALE (female “i,” 2.70 mm).—Article 3 of antenna 1 slightly smaller than article 2, lacking aesthetascs, article 2 with one apiconventral seta and 2 setules, article 1 of flagellum not enlarged. Article 4 of antenna 2 with additional 3 dorsal setae near base. Article 1 on outer ramus of uropod 3 slightly more strongly spinose, lateral spines = 2–3–3–2, medial spines = 1–2–2–2, medial setae = 1–1–0–0.

VARIABLES.–Aspects of articles 1–3 of antenna 2 shown as several illustrations, these articles inferior, small, articulate but difficult to replicate.

Rami of uropods 1–2, and to some extent their peduncles, curled downward in all preserved specimens (several hundred specimens examined).

HOLOTYPE.—USNM 184164, male “g,” 2.70 mm (illus.)

TYPE-LOCALITY.—BLM A2–12, 39°21′36″N, 72°31′18″W, east of Atlantic City, New Jersey, 129 m, 7 Aug 1977. Material deposited in USNM.

MATERIAL.—Type-locality, male “h,” 2.70 mm (illus.); female “i,” 2.70 mm. Additional 34 BLM stations in general region, each with one or more specimens, from about Cape Henry to Georges Bank; specimens also from USNM, Fish Hawk 8832, 21 Aug 1920, 8834, off Cape Henry, Virginia, 43 fms, Albatross 2261, 40°04′00″N, 69°29′30″W, 58 fms, 28 Sep 1884.

DISTRIBUTION.—Continental shelf of Atlantic America from about Cape Henry, Virginia, to Georges Bank (40°29′N, 67°43′W), 129–175 m.