Stegocephaloides ingstadi, Jørgen Berge, 2003

Jørgen Berge, 2003, Stegocephalidae (Crustacea: Amphipoda) from Australia and New Zealand, With Descriptions of Eight New Species, Records of the Australian Museum 55, pp. 85-112 : 103-106

Stegocephaloides ingstadi n.sp.

Figs. 14, 15

Type material. HOLOTYPE: AM P50234, ♀ 5 mm, 16°37.81'S 146°23.08'E, 1000 m (QLD-931), east of Flynn Reef , Queensland, Australia, 06 Jun. 1993. Collector: J.K. Lowry & party on RV “Sunbird” ( SEAS project, trap 2, transect 1).

Additional material. AM P60489, immature ♀ 4 mm, 30°10.94'S 153°32.27'E, 1000 m (NSW-863), NE of Coffs Harbour , New South Wales, Australia, 11 Aug. 1993. Collector: P. Berents & party on MV “Cheryl Lee”. AM P49967, immature 2 mm, 30°13.75'S 153°28.56'E, 300 m (NSW-881), NE of Coffs Harbour , New South Wales, Australia, 12 Aug. 1993. Collector: P. Berents & party on MV “Cheryl Lee”.

Distribution. known from the east coast of Australia (Queensland and New South Wales) at depths between 300 and 1000 m.

Diagnosis (see also Table 3): Pleonites dorsally smooth. Antenna 1 flagellum with 4 articles. Antenna 2 peduncle article 4 longer than article 5. Epistome not produced laterally, epistomal plate absent. Labrum longer than broad, left lobe reduced. Mandibular incisor toothed, lateral. Lacinia mobilis powerful, expanded laterally. Maxilla 1 outer plate with ST in a pseudocrown, palp uni-articulate. Maxilla 2 outer plate gaping and geniculate. Maxilliped palp dactylus simple and pointed. Pereopod 6 basis posteriorly expanded, expansion rudimentary. Uropod 3 outer ramus 2-articulate. Articulation between urosomites 2 and 3 absent. Telson longer than broad, pointed, cleft.

Description. Rostrum reduced, inconspicuous. Antenna 1 as long as antenna 2; accessory flagellum article 2 present. Antenna 2 peduncle articles 3–5 longer than flagellum; article 3 short, about as long as broad. Epistome curved (convex) and smooth. Maxilla 1 palp not reaching above the apex of outer plate; outer plate distally rectangular; ST first row with 6 setae (ST1–5, ST7); ST 6 absent; gap between ST 5 and ST 7 present; ST A present, located distally, part of first row; ST B present, part of second row; ST C present; inner plate with pappocuspidate setae. Maxilla 2 outer plate setae with distal hooks, distal cleft absent; inner plate setae row A covering about two thirds of the margin, clearly separated from row B; row A setae pappose; row B setae proximally simple; distally with cusps present; row C present; row D present, row elongated towards and beyond row A, setae with many small cusps distally. Maxilliped palp 4-articulate; article 2 distally not produced; inner plate not exceeding base of palp article 2; 2 nodular setae; medial setae-row reduced and transverse, setae simple; distal setae-row present; inner setae-row not reduced, setae not conspicuously large; outer plate with outer setae-row marginal with setae attached in a deep hollow, setae short and strongly curved upwards (hooks); inner setae-row reduced with short and simple setae; distal setae-group present, setae short simple. Labium with a distal pointed projection. Coxae and bases on the pereopods covered with setae; setae very short. Coxae 1–3 contiguous.

Pereopod 1 coxa about as deep as basis; propodus subrectangular but distally narrowing. Pereopod 2 longer and thinner than pereopod 1; ischium not elongate, distal posterior margin with plumose setae; propodus subrectangular but distally narrowing, palm absent. Pereopod 4 basis posterior margin with long setae; ischium with plumose setae on distal posterior margin. Pereopod 6 basis submarginally with a row of long plumose setae. Pereopod 7 basis anterior margin straight, distally rounded; medial row of setae present, setae short and robust. Oostegites on pereopods 2–5, gills on pereopods 2–7.Uropods: Uropod 1 peduncle longer than rami; outer ramus weakly longer than inner. Uropod 2 peduncle as long as rami; outer ramus as long as inner. Uropod 3 peduncle shorter than half the length of rami; outer ramus shorter than inner. Telson longer than peduncle uropod 3; submarginal setae on apex of each lobe absent.

Male. Unknown.

Etymology. The present species is named after the Norwegian scientist, explorer and writer Helge Ingstad (1899–2001).

Ingstad discovered remains of Viking settlements in North America built 500 years before the arrival of Columbus.

Remarks. J.L. Barnard (1967) described Stegocephaloides camoti based upon a single specimen, which unfortunately has been inaccessible for examination. However, the material examined and described herein does show some distinctive and important differences from the holotype of S. camoti (see Table 4). First of all, J.L. Barnard (1967: 148) describes the first article of the flagellum of antenna 1 as “flattened and inflated (from lateral view)”, and figures a distinctive crenulated distal projection on the labium. In S. ingstadi , the antenna 1 flagellum is round (the normal condition in the family), and the distal projection on the labium is pointed. Furthermore, S. ingstadi has the outer ramus on uropod 3 shorter than inner ramus, versus longer in S. camoti . Thus, although the two specimens appear to be closely related, a new species is erected for the Australian material.