Austronanus mawsoni Just & Wilson, 2006, sp. nov.

Austronanus mawsoni sp. nov.

(Figs 11–12)

Etymology. The species is named after Sir Douglas Mawson, Australias pre­eminent Antarctic explorer.

Material examined

Holotype. Adult Ψ, 1.35 mm, Antarctica, Davis Station, 68°34.5'S, 77°53'E, Site C, 25 January 1982, M. Tucker, NMV J4774.

Paratypes. Same data as holotype, NMV J53233 (ΨB).

Description. Body width 0.48 length in female, widest at pereonite 3. Head length 0.48 width; length posterior to eyestalks 0.65 anterior length. Frontal margin lobe length 0.40 head length; apex bluntly angular in dorsal view, margin adjacent to apex concave, sinuous. Eyestalks lateral apex somewhat flattened, long axis angling forward at approximately 40°.

Pereonite lateral margin 1–4 linear, 5–7 rounded. Pereonite 5 in dorsal view distinctly narrower than pereonites 4 and 6. Pereonite lateral margins 6–7 finely denticulate.

Pleon length 1.0 width. Pleonite 1 width 1.1 distance between uropods. Pleonite 1 length 0.2 width. Pleotelson proximal margin length shorter than lateral margin length forming 60° angle with medial axis of pleon; lateral margins denticulate, with 11 denticles per side, length of denticles subequal except for small anterior and single large posterior ones; posterior margin in female forming 100° angle, with single denticle each side.

Antennula articles 1–2 combined extending beyond eyestalk apex; article 1 length subequal to 2, broader than 2, inflated; article 2 with distoventral projection, distal articles inserting dorsally; 5–6 of subequal length, longer than articles 3–4.

Antenna article 2 lateral margin with two spines (proximal spine smaller); article 3 in ventral view inflated midlength, margins curved, width 0.50 length, with crenate flange on lateral margin, broad (width near length of small setae), with distinct scalloping; article 5 distinctly longer than article 4; flagellum with 6 articles, proximal article 2.7 length of second article.

Pereopod I basis with low crenate ridge on anterior margin, length 3.3 width; merus with 2 spines on anterior margin, 1 spine on posterior margin; carpus distal width 1.0 posterior margin length; posterior margin with 2 denticles proximal to robust setae, 2 denticles between robust setae, one denticle distal to robust setae; propodus narrowing distally to insertion of dactylus, with 1 robust setae (somewhat proximally), with crenate ridge (fine, divided at level of robust seta). Pereopods V–VII coxae lateral margin denticulate, each with 2 denticles of differing lengths.

Female operculum distal part tapering with concave distolateral margins, width 0.87 length.

Uropods on lateral margin of pleotelson.

Size. Largest female 1.35 mm.

Distribution. Known only from the type locality.

Remarks. Austronanus mawsoni sp. nov. shares with A. glacialis and A. aucklandensis a rounded apex of the head and sinuous lateral margins. Austronanus aucklandensis has only 5 articles in the antennulae as opposed to 6 in A. mawsoni. Differences between A. mawsoni and A. glacialis are discussed under A. glacialis.