Stegocephaloides tucki, 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 : 108-111

Stegocephaloides tucki n.sp.

Figs. 19–21

Type material. HOLOTYPE: AM P52713, 3 7 mm, 43°08.96'S 145°15.36'E, 1000 m (TAS-384), east of Fortescue Bay , Tasmania, Australia, 17 Apr. 1993. Collector: J.K. Lowry & party on MV “Tasmanian Enterprise” ( SEAS project trap 2, transect 2) . PARATYPES: AM P60409, 233 , 6–7 mm, 43°08.96'S 145°15.36'E, 1000 m (TAS-384), east of Fortescue Bay , Tasmania, Australia, 17 Apr. 1993. Collector: J.K. Lowry & party on MV “Tasmanian Enterprise” ( SEAS project trap 2, transect 2).

Additional material. MV J40623 , 1♀, 38°16.40'S 149°27.60'E, 800 m, Victoria, south of Point Hicks , 23 Jun. 1986 .

Distribution. Victoria and Tasmania, 800–1000 m.

Diagnosis (see also Table 3): Pleonites dorsally smooth. Antenna 1 flagellum with 9 articles. Antenna 2 peduncle article 4 shorter 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 produced and bifid. Pereopod 6 basis posteriorly expanded, expansion rudimentary. Uropod 3 outer ramus uni-articulate. Articulation between urosomites 2 and 3 absent. Telson longer than broad, pointed, cleft.

Description. Rostrum reduced, inconspicuous. Antenna 1 longer than 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 subrectangular; 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 pappose setae. Maxilla 2 outer plate setae with distal hooks, setae without distal cleft; 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 pappose, distally with cusps present; row C present; row D present, row elongated towards and beyond row A, with many small cusps distally. Maxilliped palp 4-articulate; article 2 distally produced; distal inner margin weakly produced; inner plate not exceeding base of palp article 2; 2 nodular setae; medial setae-row transverse, setae pectinate; distal setae-row present; inner setae-row not reduced; outer plate with outer setae-row marginal, setae short and strongly curved upwards (hooks); inner setae-row reduced, setae short and simple; distal setae-group present, setae short and simple. Labium with a distal pointed projection. Coxae and bases on the pereopods covered with setae; setae simple. Coxae 1–3 contiguous. Pereopod 1 coxa deeper than basis; propodus subovate. Pereopod 2 longer and thinner than pereopod 1; ischium elongate, ratio length to breadth exceeding 1.5, distal posterior margin with plumose setae; propodus subrectangular, palm absent. Pereopod 4 basis posterior margin with long setae; plumose setae on distal anterior margin; ischium with plumose setae on distal posterior margin. 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 as long as inner. Uropod 2 peduncle shorter than rami; outer ramus longer than inner. Uropod 3 peduncle longer than half the length of rami; outer ramus as long as inner. Telson longer than peduncle uropod 3; submarginal setae on apex of each lobe absent.

Male. Pereopod 2 propodus larger in males than in females; Urosome ordinary (similar to females).

Etymology. The present species is named after the very distinct morphology of its maxilliped palp: the dactylus is distally bifid, with one projection pointed and acute (most probably homologous to the dactylus found in other stegocephalids) and one blunt and heavily setose. The latter is distally slender but, seen from above, smooth with a dense collar of setae around. It is this arrangement of setae that the first author found similar to his childhood vision of the head of Friar Tuck, the good companion of the English hero, Robin Hood.

Remarks. This species and Stegocephaloides australis K.H. Barnard, 1916 , are the only known species within the family that possess a cleft dactylus of the maxilliped palp (see Fig. 21). These two species can be separated on the absence of an articulation on outer ramus of uropod 3 and the long antennae in S. tucki .