Compoceration garyi, Just, 2009

Just, Jean, 2009, Compoceration garyi, a new genus and species of Paramunnidae (Crustacea, Isopoda, Asellota), from south-eastern Australia., Memoirs of Museum Victoria 66 (1), pp. 81-84 : 81-84

Compoceration garyi sp. nov.

Figures 1–2

Material examined. Holotype, ovigerous female, 0.9 mm, Australia, New South Wales, off Eden 36°57.40'S 150°18.80'E, 220 m, muddy shell, WHOI epibenthic sled, 20 July 1986, Poore et al., RV Franklin , stn SLOPE 21 , Museum Victoria NMV J18982 (incl. 2 slides).

Description. Body widest between pereonites 2 and 3, width 0.42 length. Head length 0.25 width (including eyestalks); length posterior to eyestalks 0.63 anterior length. Frontal margin with low convex bulge in middle; lateral spines approximately 0.7 length of eyestalks, pointing forward at about 50° to head midline, length/width at base approximately 1.4: dorsal outgrowth at base of spine spherical, diameter approximately 1.5 spine width at base, with heavily calcified sculptured surface. Eyestalks overreaching anterior lateral corner of pereonite 1 by about 1/2 their length, pointing laterad at 90° to head midline, anterior and posterior margins parallel, apex rounded, ocelli not observed.

Pereonite 1 length half midlength of pereonite 2, 3 1.5 length of pereonite 2, 4 length equalling pereonite 2, 5 length equals pereonite 1, 6 1.3 length of pereonite 5, 7 length equals pereonite 5. Pereonite 1 lateral margins irregularly rounded truncate, broadest at midpoint; pereonites 2–7 lateral margins extended into broad-based pointed spines with fine marginal denticles; pereonites 2 and 3 spines similar, approximately 0.3 length of pereonite width, spine on 4 reduced compared to 3 and 5, spine on 5 and 6 similar to 2 and 3, on 7 slightly shorter than 6; spines on 6 and 7 pointing backward at approximately 45 degrees.

Pleon length 1.4 width. Pleonite 1 width 0.85 distance between uropods, length 0.2 width. Pleotelson without noticeable neck or shoulders, lateral margins evenly convex to level of uropods, with 9 denticles on left side (partly broken on right); posterior margin 0.33 length of entire pleotelson, broad, merging straight into lateral margin except for distal denticle of the latter, triangular at 85°, apex a tiny square knob.

Antennula articles 1 and 2 combined reaching apex of eyestalk; 3 and 4 of equal length, both 0.6 length of subequal 5 and 6.

Antenna article 1 in ventral view approximately 0.4 length of article 2 along lateral margin; article 3 width 0.3 length, with small denticle in distal half of lateral margin, narrowing in distal 1/3.

Pereopod I basis length 3.6 times width; ischium 0.5 length of basis, anterior margin with single acute spine in proximal half; merus with single acute spine on anterior margin; carpus margin distal to robust setae straight; propodus with single robust seta on posterior margin. Pereopod II propodus with 2 slender robust setae on posterior margin.

Pleopod II (female operculum) distolateral margins nearly straight, width 0.72 length.

Uropods recessed into simple non-protruding cuticle pockets, with single ramus (endopod), length 3 times width.

Etymology. The species is named for Dr Gary Poore, Museum Victoria, Melbourne, Australia, in recognition of his contributions to many aspects of isopodology, and in gratitude for much help over decades.

Discussion. Among the paramunnids with dorsally covered coxae, especially on pereonites 5–7, the new genus Compoceration share several characteristics with Pentaceration Just, 2009 : spines on the frontal margin of the head; elongate eyestalks; article 2 of the antennal peduncle about 3 times longer than 1; pereopod I carpus oval; pereonites 2–7 laterally extended into spines; pereonite 4 width reduced (although not as strongly as in Pentaceration ). Compoceration differs from Pentaceration (character in parentheses) as follows: front margin of head with 2 lateral spines with dorsal outgrowth at their base (3 spines, 1 mid-frontal, 2 lateral, no basal outgrowth); eyestalks 4 times longer than wide (2–3 times); mandible molar cylindrical, not distally expanded (strongly expanded distally, ‘flared’). By analogy with Pentaceration , it is possible that these differences are more strongly expressed in the as yet unknown males of Compoceration .

Species in Paramunna also have head ornaments, but they are in the shape of 2 dorsomarginal broad, square or rounded lobes (small pointed lobes in one species) that do not appear to be homologous with the above mentioned frontal margin spines. Generally Paramunna species have ovoid bodies with rounded to truncate pereonite margins. Only in terminal males of Paramunna bilobata Sars, 1866 and the somewhat aberrant P. walvisensis Just and Wilson, 2004 are pereonites extended laterally into broad pointed laplets, especially on the last 3 pereonites. Paramunna species otherwise differ from Compoceration in most other diagnostic characters: peduncle article 2 of antenna short, about as long as 1; eyestalks about as long as wide, not overreaching pereonite 1; mandible molar expanded distally, ‘trumpet-shaped’; pereopod I carpus triangular; pereonite 4 similar to 3 and 5; uropods inserted in pleotelson margin, not on dorsal surface, bi-ramous.

Figures

Figure 1. Compoceration garyi gen. et sp. nov. Holotype, ovigerous female. a, antenna; au, antennula; c, enl, dorsal view of head enlarged; cv, ventral view of head; p1 and 2, pereopods I and II; up, uropod. Scale bar for habitus: 0.5 mm.

Figure 2. Compoceration garyi gen. et sp. nov. Holotype, ovigerous female. mdr, right mandible, with enlargement; mdl, left mandible; mxp, maxilliped; op, female operculum (pleopod II); pl3 and 4, pleopods III and IV; pt vv, pleotelson, ventral view.