Munnogonium globifrons ( Menzies, 1962 )

Just, Jean & Wilson, George D. F., 2021, Redescriptions and new species in the ‘ Austrosignum-Munnogonium’ complex sensu Just & Wilson (2007), mainly from the Southern Hemisphere (Crustacea Isopoda: Paramunnidae), Zootaxa 4952 (3), pp. 401-447 : 431

Munnogonium globifrons ( Menzies, 1962)

( Fig. 18 )

Austrosignum globifrons Menzies, 1962: 52 , fig. 10.

Munnogonium globifrons .— Bowman & Schultz, 1974: 266; Just & Wilson, 2007: 22, table 1.

Type fixation. Holotype, ♂, SMNH 3221 .—Original designation.

Remarks on type material. Menzies (1962: 52) stated that the type locality yielded 3 males and 3 females. SMNH 3221 contained one microvial with the presumed male holotype that was missing pleopod I. One juvenile female labelled ‘allotype’ was found in the vial with the holotype. Additionally, one small male, one female with anterior parts missing, and two juvenile females were found in a separate microvial. We presume that these five additional specimens are the paratypes.

Type Locality. Magellan Strait, South of Punta Arenas, Chile.

Material examined. Holotype. ♂ (pleopod I missing), 1.1 mm, Chile, Magellan Strait , near the estuary of Rio los Ciervos , South of Punta Arenas , 53°11’S, 70°55’W, tidal belt, gravel and clay, mixed with mud and covered with boulders; exposed kelp; 3 May 1949, Lund University Chile Expedition 1948–49, stn M115, SMNH 3221 .

Paratypes. Same data as holotype, SMNH Type-8818, (1 juv. ♀ (labelled allotype, in microvial with holotype), 1 small ♂, 1 ♀ anterior parts missing, 2 juvs ♀) .

Description (male). Body widest at pereionites 3–4 (5 appears somewhat flattened). Dorsally with scattered setae. Head length 0.65 width; length posterior to eyestalks 1.3 anterior length. Frontal margin broadly rounded without angular lateral margins adjacent to antennae. Eyestalks length equals width, apex a rounded bump, long axis angling forward at 40°.

Pereionite 1 sagittal length 3 times pereionite midline length. Pereionites 1–7 lateral margins rounded. Coxal plates 1–7 rounded, visible in dorsal view.

Pleon length 1.6 width. Pleonite 1 proximal width equals distance between uropods, length 0.4 width. Pleotelson laterally convex, smooth, lacking inflection between lateral and proximal margins; posterior projection forming 70° angle, evenly curving into lateral margin, apex narrowly rounded.

Antennula article 1 much longer than eyestalk, slightly curved, tubular, shorter than 2, width subequal to 2, reaching to or just beyond pereionite 1 lateral margin, articles 4–6 of subequal length, all shorter than 3. Antenna in ventral view tubular, width 0.25 length.

Pereiopod I basis anterior margin smooth, length 2.4 width; ischium smooth, merus with few simple setae, carpus narrowly triangular, distal width equals posterior margin length, posterior margin with 3 subequal robust setae, with 1 fimbriate projection proximal to middle robust setae; propodus narrowing distally to insertion of dactylus, with fimbriate opposing margin and a few simple setae. Pereiopod II carpus and propodus with long slender robust setae on posterior margin; unguis much longer than dactylus, ventral claw slender, as long as dactylus.

Male pleopods I lateral lobes distinctly projecting from lateral margin, width 0.3 distance to midline, distal sublobe with curved robust seta on apex; each distal projection forming acute angle of about 30°, with blunt apices.

Uropods on lateral margin of pleotelson, protopod absent or hidden.

Size Largest male 1.1 mm.

Distribution. Magellan Strait, Chile. Intertidal.

Remarks. Munnogonium globifrons differs from all congeners by the proportionately much larger head relative to the rest of the body, and by the presence of a curved robust seta on each lateral lobe of pleopod I.

Figures

FIGURE 18. Munnogonium globifrons (Menzies, 1962), holotype, ♂. a, antenna; au, antennula; cvv, head ventral view; p2, pereiopod I; pl1–2, pleopods I–II; up, uropod. Scale for habitus, 0.5 mm.