Petalosarsia australis sp. nov.

(Figs. 19–21)

Material examined. Holotype subadult male, 4.6 mm (AM P85740), Tasman Sea, 40°45ˏ56ˏ S, 149°01ˏ37ˏ E – 40°46ˏ32ˏ S, 149°01ˏ16ˏ E, 2400-2500 m (FR1086-04), 10 December 1986. Paratype ovigerous female, dissected, missing pleonite 6-uropods (AM P85739), Tasman Sea, 40°45ˏ56ˏ S, 149°01ˏ37ˏ E – 40°46ˏ32ˏ S, 149°01ˏ16ˏ E, 2400-2500 m (FR1086-04), 10 December 1986.

Description. Ovigerous female (Figs. 19-21). Body not well calcified, covered with minute scale like sculpture. Carapace (Figs. 19 A, C), oval seen from above, length 1.58 times depth, length 1.19 times width. Dorsal surface flat, surrounded by a pair of weak dorsolateral carinae; ventral margin smooth, anterolateral angle and antennal notch obsolete; pseudorostrum short, 0.1 times length of carapace. Width of small, triangular eye lobe 0.1 times width of carapace. Pereon 0.7 times carapace length. Pleon broken off at posterior border of pleonite 5.

Antenna 1 (Fig. 19 D) 1st article of peduncle 0.75 times combined length of 2nd and 3rd articles; main flagellum of 3 articles, 0.7 times basal article of peduncle; 1st article of main flagellum 1.2 times distal 2 articles combined; accessory flagellum minute. Antenna 2 (Fig. 19 D, E) of 3 articles, with a pappose seta on distal end of article 1 and article 3. Mandibles, maxilla 1 and maxilla 2 are normal for the genus (Fig. 19 F-H).

Maxilliped 1 (Fig. 20 A) basis shorter than distal segments together. Maxilliped 2 (Fig. 20 B) basis 1.30 times combined length of following 4 articles; blunt spines absent near distal end of basis. Maxilliped 3 (Fig. 20 C) basis 1.2 times distal articles together, with 2 plumose setae on inner margin.

Pereopod 1 (Fig. 20 D), basis 1.16 times combined length of ischium and carpus, with 4 pappose setae on inner margin; length of carpus 2.4 times width, 3.7 times dactylus length, 0.7 times basis length. Pereopod 2 (Fig. 20 E) basis 0.8 times distal articles together, with 3 long plumose setae and several short setae on inner margin; exopod reaching distal end of basis. Pereopod 3 (Fig. 21 A), basis slender, 1.8 times combined length of distal articles; biarticulate exopod present, tiny. Pereopod 4 (Fig. 21 B), basis slender, 1.3 times remaining distal articles; uni-articulate exopod present. Pereopod 5 (Fig. 21 C), basis 0.8 times distal articles together.

Telson and uropods missing.

Holotype subadult male (Fig. 19 B). Overall appearance similar to ovigerous female. Carapace length 0.3 times total body length; pseudorostrum 0.16 times length of carapace. Pereon Iɵnǥtʰ 0.55 times carapace length. Pleon length 0.56 times total body length, with 2 pairs of pleopods.

Uropod (Fig. 21 D), peduncle 1.1 times pleonite 6 length, 0.5 times exopod length, and at most 0.37 times endopod length; exopod at most 0.8 times endopod length; endopod with 8 stout setae with single setule on inner margin, proximal part of medial margin lined with fine hair-like setae. Telson subquadrate, 0.47 times pleonite 6 length.

Etymology. The species name is from the Latin austral, meaning south, referring to the location of collection being in the Tasman Sea in the Southern Hemisphere.

Distribution. Tasman Sea, 2400–2500 m depth.

Remarks. This is the first record of the genus Petalosarsia, and the first certain record of a pseudocumatid cumacean, from the Southern Hemisphere. The present species is characterized by the combination of (1) faint dorsolateral carina, without teeth, running for entire length of carapace, (2) female antenna 2 tri-articulate, (3) basis of maxilliped 2 without projections or spines, and (4) medial margin of pereopod 1 carpus being a constant curve from the articulation with the merus to the articulation with the propodus, without a distinct medial and distal margin or acute distomedial corner.