Pentaceration denticornis Just, 2011, sp. nov.

Pentaceration denticornis sp. nov.

Figures 1–3

Type fixation. Holotype, male, here designated.

Etymology. The epithet alludes to the lateral and dorsal denticles on the head spines.

Material examined. Holotype, 3, 2.20 mm, Australia, Tasmania, Off Freycinet Peninsula, 42o0.20'S, 148o37.70'E, 720 m, coarse shelly sand, WHOI epibenthic sled, M.F. Gomon et al, RV Franklin, 27 July 1986, stn SL46, NMV J20045 (with 2 slides).

Paratypes (7 specimens). Same data as holotype, NMV J20043 (3 3, 1 ovigerous Ƥ, 1 damaged specimen). Same data as holotype, NMV J20044 (2 recently spent Ƥ, the one illustrated 2.26 mm).

Description (male, holotype). Body tapering from pereonite 1 to pleon; width 0.25 length, widest between pereonites 1 and 2 and 2 and 3. Head length 0.28 width, length posterior to eyestalks equals anterior length. Frontal margin mid-spine length equals combined mid length of pereonites 1–3, slender, pointed, with numerous lateral and dorsal denticles; lateral spines as long as mid spine, with similar denticles, diverging at 105°. Eyestalks overreaching pereonite 1 with at least half their length, pointing forward at approximately 15º, tapering to acute point, slightly up-turned in distal half, with denticles along anterior margin.

Pereonites 1–7 each with single middorsal slender, upright spine arising from broad base. Pereonite 1 lateral margins slightly concave in anterior half, posterior half evenly convex with marginal denticles; pereonites 2–3 with acute lateral spines, diverging 35–40° from each other, slightly up-curved, similar to lateral head spines but more slender, length approximately 0.7 pereonite width; pereonite 4 margins with tiny mid lateral point; pereonites 5 lateral spines similar to 3 but slightly shorter; spines on 6 the longest, approximately 1.4 length of pereonite 2 spines, pointing backwards at approximately 45° to body mid-line; pereonite 7 with small backward pointing spines, approximately twice length of pereonite 4 spines. Pereonites 5 and 6 with posterior lobes overlapping succeeding pereonite, with single simple seta on lobe surface.

Pleon length 1.85 width. Pleonite 1 width 0.7 distance between uropods, length 0.25 width. Pleotelson with distinctive proximal neck; denticulate lateral margins nearly straight, diverging somewhat distally; 10 denticles on broad, translucent flange; distal projection drawn out to long, pointed spine, approximately 0.55 length of entire pleotelson.

Antennula articles 1 and 2 combined reaching approximately to apex of eyestalks; article 1 shorter and wider than 2, tubular; 3 and 4 of equal length, 0.7 length of subequal 5 and 6.

Antenna article 2 in ventral view 3.5 length of 1, oval, with few acute denticles in mediodistal half; article 3 width 0.3 length, with few acute spines in laterodistal corner; article 5 length 3.0 times 4; 6 length 1.45 times 5; flagellum with 9 articles, proximal article length subequal to combined articles 2 and 3 length.

Pereopod I basis length 3 times width, anterodistal margin with row of large blunt spines; ischium 0.65 length of basis, with similar row of anterior spines; merus with single anterior acute spine; carpus broadly oval, posterior margin with acute spine in front of distal most robust seta; propodus narrowing distally to insertion of dactylus, with 2 robust setae and crenate flanges on opposing margin. Pereopods II–VII slender; pereopod II propodus with 3 slender robust setae on posterior margin.

Pleopod I lateral sublobes similar, rounded, partly overlapping; width 0.27 distance to midline; distal projection length 0.36 pleopod total length, forming acute angle, with pointed apices. Pleopod II protopod pointed distally, lateral margin with simple setae; endopod article 2 (stylet) forming approximately 130° curve.

Uropods recessed into protruding cuticle tube with large medial projection; protopod hidden, exopod absent; endopod length 3 times width.

Female. Ovigerous females have shorter body spines, especially on head front and pereonite 2; lateral head spines diverging approximately 135°; eyestalks pointing backward at 15°; pereonite 1 lateral parts less strongly developed than male; pereonites 2–4 wider, more vaulted dorsally; operculum (pleopod II) ovoid, pointed, with straight distal margins, width 0.62 length.

Size. Largest male, 2.20 mm; largest spent female, 2.26 mm.

Distribution. Australia, eastern Tasmania, 720 m.