Tytthocope sulcifrons Barnard 1920

Tytthocope sulcifrons (Barnard, 1920)

(Figs 24 – 29)

Eurycope sulcifrons Barnard, 1920: 421 (Plate XVII. Figs 22, 23); Kensley, 1978: 125 –127. Tytthocope sulcifrons Wilson & Hessler, 1981: 412.

Material examined. Type series: 6 specimens SAM-A 4063 P.F. 17440, Cape Point N. 89°E, distance 36 miles, 700 fathoms. Bottom: green mud. Lectotype: male, 3.3 mm, without pleopods, (pleopods are in a separate slide), paralectotypes: female (2.5 mm), female with oostegites (f. oost.) 3.9 mm, female without antennas, 2.6 mm, female 3.45 mm, female about 4.0 mm (cephalothorax nearly broken off).

Diagnosis. Rostrum with weak lateral keels, anterior margin sloping, with two setae. Antennula article 1 width 0.7 rostrum width and length 0.75 rostrum length. Pleotelson length 0.75–0.8 width, length 0.45 natasome length. Pereonite 5 length 0.3 pleotelson length, 0.65 pereonite 6 length medially, pereonite 7 length 0.24 pleotelson length, 0.2 pereonite 6 length medially, longer than pereonite 1. Maxilliped palp article 4 distomedial lobe longer and broader than article 5. Male pleopod 1 gradually tapering towards rounded distal margin.

Description. Body (Figs 24, 25) length 2.2 (male) 2.4 (f) 2.15 (f. oost.) width of pereonite 5, body height 0.35 body length. Cephalothorax (Fig. 26 b) length 0.5–0.6 width, length behind antennula insertion 0.45–0.5 antennula article 1 length; rostrum length 0.7 cephalothorax length. Rostrum with weak lateral keels, anterior margin sloping, with two setae, width between bases of antennulae subequal to rostrum length, width 1.35 antennula width. Clypeus 1.6 as wide and 0.5 as long as labrum. Anterolateral margins of coxae of pereonites 2–4 not projected in dorsal view. Natasome length 0.6 body length, width 1.5 cephalon width; pereonite 5 lateral length subequal to pereonites 6 lateral length; pereonite 6 longest medially, length 1.8 pereonite 5 length, pereonite 7 0.6–0.7 pereonite 6 length laterally. Anterolateral margins of pereonites 5–7 and pleotelson with distal seta; ventral bump of posterior part of pereonite 6 most pronounced. Pleotelson length 0.75–0.8 width, 0.3 body length, preanal ridge not projected.

Antennula of male (Fig. 29 a) more than 0.35 of body length (distal part broken off); article 1 nearly reaching slope of rostrum, length 1.25 width, article 2 length 1.3 width, 0.5 length and width of article 1; article 3 length 0.4 of article 2; article 4 length 0.8 article 3 length, article 5 shorter than article 4, following articles (more than 19) subequal in length to article 4.

Antenna incomplete on all specimens: articles 1–4 subequal in size, scale on article 3 triangular, with few distal setae.

Mandible (Fig. 27 a,b) incisor process with 2 cusps; lacinia mobilis of left mandible almost as long as incisor, with 4 teeth; spine row with 7 and 9 spines on left and right mandibles respectively; molar process as long as incisor process, tapering with 3 distal teeth; condyle length 0.2 mandiblular body length, equal to molar process length; palp slender, length 0.8 mandibular body length, article 1 with 5 medial setae, article 2 length 2.3 article 1 length, with 2 stout distal setae, article 3 with row of lateral short setae and 3 long setulated distal setae. Maxilla 1 (Fig. 27 c) lateral endite width 1.2 mesial endite width, with 12 distal spine-like setae, longest distolateral seta length 1.3 endite width. Maxilla 2 (Fig. 27 d) middle endite shortest, lateral endite longest, mesial endite with 4 strong and numerous slender distomedial setae, lateral and middle endites with 2 long and 2 shorter distal setae each, lateral endite with an additional slender distomedial seta. Maxilliped (Fig. 29 c) basis length 2.6 width, endite width 0.5 basis width, with 5 coupling hooks, distal margin slightly concave, with numerous simple slender and few stout setae, lateral margin rounded; palp inserted after 0.4 length of basis, article 1 with long distolateral seta, lateral length 1.3 medial length; article 2 width 1.3 basis width and 2.3 endite width, lateral length 2.6 medial length, lateral margin slightly convex with 2 small setae, distolateral projection reaching distolateral margin of article 3; article 3 width 0.9 article 2 width, medial length 1.6 article 2 medial length, medial margin smooth, with 7 setae; article 4 medial lobe elongate, slightly longer than article 5, with 3 distal setae; article 5 length 0.7 article 4 lateral length, with 4 distal setae. Epipod length 2.5 width.

Pereopods incomplete, pereopods 1–4 broken off, pereopods 5 and 6 with propodus and dactylus broken off, pereopod 7 with dactylus broken off (Fig. 28). Pereopod 5 (Fig. 28 a) length ratios of ischium–carpus to basis: 0.8, 0.25, 1.1; basis length 3.9 width, with 3 small dorsal setae; ischium length 3.5 width, with 7 ventral setae; merus length 1.6 width, with 1 ventral seta; carpus length 1.25 width, with 25 sockets from dorsal plumose setae. Pereopod 6 (Fig. 28 b) similar in shape to pereopod 5, length 1.05 pereopod 5 length, basis slightly (1.1) longer, ischum slightly shorter (0.9) than these articles of pereopod 5, length ratios of ischium–carpus to basis: 0.6, 0.2, 0.95; basis length 4.9 width, with 6 ventral setae; ischium length 3.4 width, with 2 ventral setae; merus length 1.1 width; carpus length 1.3 width. Pereopod 7 (Fig. 28 c) basis–carpus length 0.6 pereopod 6 basis–carpus length, length ratios of ischium–propodus to basis: 0.6, 0.2, 1.7, 1.1, 0.8; carpus length 1.6 width, propodus length 1.56 width; ischium, merus and carpus with distoventral UB long seta.

Pleopod 1 (Fig. 29 d) gradually tapering towards rounded distal margin, length 1.8 basal width, distal lobes not separated. Pleopod 2 (Fig. 29 f) protopod semicircular, length 2.2 width, stylet length 0.5 protopod length; exopod as broad as basal part of endopod, inserted on 0.3 of protopod length from distal margin. Pleopod 3 (Fig. 26 c) endopod length 1.1 width, three distal plumose setae located more medially, length about half of endopod length; exopod 1.8 length and 0.25 width of endopod, distal article separated, length 0.35 basal article length, with distal plumose seta, as long as endopod setae. Pleopod 4 (Fig. 26 d) endopod length 1.1 width, exopod of two articles, length 0.9 endopod length, width 0.5 endopod width, distal plumose seta slightly longer than setae on pleopod 3. Pleopod 5 (Fig. 26 e) length 1.3 width.

Uropod (Fig. 26 f) 0.1 pleotelson length. Protopod length 0.85 width, slightly broadened distally; endopod length 2.0 protopod length, distally with 1 simple and 4 broom setae; exopod 0.6 of endopod length and 0.3 width, with 1 broom and 1 simple seta distally.

Remarks. T. sulcifrons together with T. divae sp. nov. belongs to the same group which differs from the T. megalura group by the characters which have already been described above.

Distribution. The species is only known from the type locality, the southern Atlantic off the South African coast, at depth of 1280 m.