Pentaceration bifida, 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 : 35-37

Pentaceration bifida sp. nov.

Figure 25

Type fixation. Holotype, male, here designated.

Etymology. The epithet alludes to the bifid tips of head and pereonite spines.

Material examined. Holotype, 3, 1.1 mm, Australia, Arafura Sea, 9°13'39"S, 133°41'54"E, 151 m, poorlysorted calcareous slightly sandy mud, sand & grains of forams and mollusc fragments, RV Southern Surveyor SS0505/stn. 30, Smith-Macintyre Grab, 13 May 2005, AM P83765.

Paratype. Australia, Arafura Sea, 9°09'15.6"S, 133°29'4.8"E, 174 m, poorly sorted calcareous gravelly mud with one cobble of coarse limestone, RV Southern Surveyor SS0505/stn. 55, Smith-Macintyre Grab, 21 May 2005, AM P83764 (1 Ƥ manca).

Description (male, holotype). Body square; width 0.38 length, widest between pereonites 1 and 2 and 2 and 3. Head length 0.45 width; length posterior to eyestalks 1.2 anterior length. Frontal margin middle spine length equals head length; lateral spines slightly inward curved distally, 1.66 length of middle spine, diverging at 115°. Head spines with bifid apex. Eyestalks overreaching pereonite 1 with 1/3 their length, pointing directly laterad, apex blunt with few denticles.

Pereonite 1 lateral margins rounded, weakly denticulate; pereonite 2 and 3 lateral spines diverging at 20°, similar to lateral head spines, 2 longer than 3, 2 length approximately half pereonite width; pereonite 4 lateral margins tapering to acute point; pereonites 5–6 lateral spines about as long as pereonite 3 spines, on 5 narrow with denticulate anterior margin, 6 and 7 spines with broad rounded anteroproximal lobe; pereonites 2–3 and 5–6(7) lateral spines with bifid apex.

Pleon length 1.2 width. Pleonite 1 width 0.75 distance between uropods, length 0.2 width. Pleotelson proximal and lateral margins joining without inflection, lateral margins convex, with 12–13 denticles; distal projection triangular at 80°, 0.33 length of entire pleotelson, with acute apex.

Antennula articles 1 and 2 combined at least reaching beyond apex of eyestalks (see Fig. 25 , F); article 1 tubular, (2 foreshortened in Fig. 25 au); 3 1.4 length of 4, 4 and 5 of equal length, 6 0.8 length of 5.

Antenna (article 1 could not be observed); article 3 width 0.3 length; 5 length 2.4 times 4; 6 1.75 length of 5; flagellum with 8 articles, first flagellar article 1.3 length of article 2.

Pereopod I (basis and ischium not observed), merus with simple rounded anterior margin; carpus appears triangular, but some foreshortening possible, posterodistal margin straight; propodus narrowing distally to insertion of dactylus, with 2 robust setae on opposing margin.

Pleopod I lateral sublobes unequal, proximal one rounded triangular, barely overlapping smaller, flat-tipped distal one; width approximately 0.3 distance to midline; distal projection length 0.31 pleopod total length, forming 80° angle, with bluntly pointed apices.

Uropods recessed into simple cuticle fold, protopod, if present, hidden, exopod apparently absent; endopod length 2.5 width.

Female. The single paratype is a female manca (pereopod 7 not developed). It shares the general body characteristics with the male, including bifid tips on head and body spines.

Size. Largest male, 1.1 mm.

Distribution. Australia, Arafura Sea, 151– 174 m.

Figures

FIGURE 25. Pentaceration bifida sp. nov. Holotype, 3, except F, paratype, female manca. a, antenna; au, antennula; cv, head ventral view; p 1, pereopod 1; pl 1, pleopod 1; up, uropod. Habitus scale for both: 0.5 mm.