Pentaceration magna, Just, Jean, 2011

Just, Jean, 2011, Remarkable Australasian marine diversity: 18 new species in Pentaceration Just, 2009 (Crustacea, Isopoda, Paramunnidae), Zootaxa 2813, pp. 1-54 : 16-19

Pentaceration magna sp. nov.

Figures 10–11

Type fixation. Holotype, male, here designated.

Etymology. The epithet reflects that this is the largest Pentaceration species so far recorded.

Material examined. Holotype, adult 3, 3.43 mm, Australia, Victoria, 76 km S of Point Hicks, 38o29.33'S, 149o19.98'E, 1840– 1750 m, sandy mud, fine shell, WHOI epibenthic sled, G.C.B. Poore et al, RV Franklin, 26 October 1988, stn SL 69, NMV J20047 .

Paratypes (22 specimens). Same data as holotype, NMV J60996 (4 3, 7 Ƥ). Same data as holotype, NMV J20046 (2 Ƥ, 1 3). Australia, Tasmania, 54 km ENE of Cape Tourville, 41o57.30'S, 148o58.54'E, 1770– 1735 m, coarse biogenic rubble, WHOI epibenthic sled, G.C.B. Poore et al., RV Franklin, 30 October 1988, stn SL 82, NMV J20048 (3 3, 4 Ƥ).

Description (male, holotype). Body elongate with nearly parallel sides; width 0.34 length, widest between pereonites 5 and 6. Head length 0.35 width, length posterior to eyestalks 1.3 anterior length. Frontal margin midspine length 1.3 head length, pointed, with small irregular lateral; lateral spines as long as mid spine, with similar denticles, diverging at approximately 120°, up-curved. Eyestalks overreaching pereonite 1 with at least half their length, pointing almost directly laterad, tapering to acute point, strongly up-curved 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 rounded with marginal denticles; pereonites 2–3 with acute strongly up-curved lateral spines, diverging at 20–25° from each other, similar to lateral head spines, length approximately 0.7 pereonite width; pereonite 4 with slender mid lateral points; pereonites 5 and 6 lateral spines similar to 2 and 3, 6 longer than 5, with posterior lobes overlapping succeeding pereonite, with sparse fringe of simple setae along lobe margin; pereonite 7 with small backward pointing spines. Tumaculae not present.

Pleon length 1.5 width. Pleonite 1 width 0.9 distance between uropods, length 0.12 width. Pleotelson without proximal neck; denticulate lateral margins evenly convex with 12 denticles; distal projection moderately long, pointed spine, approximately 0.4 length of entire pleotelson, up-turned, (more so than shown in the paratype 3, Fig. 10 , M l).

Antennula articles 1 and 2 combined reaching approximately to apex of eyestalks; article 1 shorter and wider than 2, tubular; 3 and 4 of subequal length, 0.75 length of subequal 5 and 6, (articles 4 and 6 slightly foreshortened in Fig. 11 au).

Antenna article 2 in ventral view about 2.3 length of 1, oval; article 3 width 0 25 length, with few small acute spines in laterodistal corner; article 5 length 4.0 times 4; 6 length 1.45 times 5; flagellum with 10 articles, proximal article as long as 2 and 2 plus 1/3 of 4 combined.

Pereopod I basis length 4.0 width, anterodistal margin with row of unequal sized blunt spines; ischium length 0.55 length of basis; carpus narrow oval; propodus narrowing distally to insertion of dactylus, with 2 robust setae on opposing margin. Pereopods II–III basis with spines on anterior margin similar to pereopod I, propodus with 3 slender robust setae on posterior margin.

Pleopod I lateral sublobes of equal length, distal sublobe rounded, proximal one bluntly triangular, width 0.2 distance to midline; distal projection length 0.3 pleopod total length, forming acute angle, with pointed apices. Pleopod II protopod broadly rounded distally, lateral margin with simple setae; endopod article 2 (stylet) forming approximately 120° curve.

Uropods recessed into irregular, spinose cuticle tubes; protopod hidden; exopod present, tip with 2 setae protruding from cuticle tube; endopod length 2.75 width.

Female. Adult (spent) females ( Fig. 10 F) have shorter and broader lateral spines on pereonites 2 and 3, but slightly longer and stouter spines on pereonites 4 and 7; pereonites 2 and 3 spines diverging at 40°; pereonites 2–4 wider, more vaulted dorsally; operculum (pleopod II) ovoid, pointed with nearly straight distal margins, width 0.7 length.

Size. Largest male, 3.43 mm; largest female (spent), 4.2 mm.

Distribution. Australia, eastern Bass Strait slope to eastern Tasmania, 1725–1840 m.

Figures

FIGURE 10. Pentaceration magna sp. nov. H, holotype, 3; F, paratype, Ƥ; M, paratype 3, d, dorsal, l, lateral views; up, uropod. Scale bars: 0.5 mm.

FIGURE 11. Pentaceration magna sp. nov. Holotype, 3, except M, paratype, 3, stn SL 82, and F, paratype, ƤA. a, antenna; au, antennula; cv, head ventral view; mdp, mandible palp; op, operculum (pleopod 2); pl 1 – 2, pleopods 1 and 2; p 1, pereopod 1.