Pseudoarthrura tuberculata Larsen, 2013, n. sp.

Pseudoarthrura tuberculata n. sp.

(Figs. 5 & 6)

Material examined. Holotype: non-ovigerous female (Reg. # ZMH K-43958), ANDEEP II, DZMB-HH 10590, station 139, 58 °14.10’S, 24°21.22’W, 3941 m, 14 March 2002, EBS-supra. Paratypes (Reg. # ZMH K-43959 & ZMH K-43960): one non-ovigerous female (dissected), two non-ovigerous females same data as holotype.

Diagnosis. Female. Maxilliped endite with inner tubercles and outer setae; palp article 2 with outer seta. Pereopods 1 to 3 propodus with dorsal seta. Uropodal exopod minute.

Etymology. Named after the maxilliped endite tubercles.

Description. Body from holotype (1.95 mm) appendages from adult female paratype.

Body (Fig. 5 A). About nine times as long as wide. Lateral shoulders inconspicuous. Cephalothorax with smooth lateral edges in dorsal view. Longer than wide. Shorter than the lengths of pereonites 1 and 2 combined. Eye-lobes absent. Pereon with pereonites gently curved. Pereonites 1 and 6 wider than long. Pereonites 2 to 5 longer than wide. Pleon short (including pleotelson only 0.15 times total body length), no visible lateral edges of dorsal shield. Pleotelson shorter than the lengths of three last pleonites combined, acorn-shaped, apex blunt, with two pairs of terminal setae, and covered by a dorsal plate.

Antennule (Fig. 5 B). Shorter than cephalothorax, with four articles plus terminal cap-like article. Article 1 longer than rest of antennule, with two simple and one setulose subdistal setae. Article 2 longer than article 3, with two setulose and two simple subdistal setae. Article 3 half as long as article 4, with one simple distal seta. Article 4 with one simple distal seta. Terminal article with three simple setae and one aesthetasc.

Antenna (Fig. 5 B). With six articles. About three quarters as long as antennule. Article 1 fused to cephalothorax, naked. Article 2 longer than article 3, naked. Article 3 with one dorsal seta. Article 4 longer than each of the other articles, with one setulose and two simple distal setae. Article 5 longer than article 2, with one distal simple seta. Article 6 minute, with three long and two shorter distal setae.

Mouthparts. Labrum not recovered. Mandibular molar slightly tapering but with well-developed crushing surface and several distal denticles. Left mandible (Fig. 5 D) lacinia mobilis as long as incisor; incisor simple. Right mandible (Fig. 5 C) incisor broad and blunt. Labium (Fig. 5 E) one pair of lobes with weakly demarcated and weakly setulose distal process. Maxillule (Fig. 5 F) endite with eight spiniform distal setae; palp not recovered. Maxilla (Fig. 5 G) ovoid. Maxilliped (Fig. 5 H,I) basis naked. Endites with two unarticulated tubercles and outer subdistal seta. Palp article 1 naked; article 2 with three simple setae on inner margin and one outer seta; article 3 with three simple inner setae; article 4 with five inner and one small outer setae. Epignath (Fig. 5 J) elongated and sharply tapering, without terminal seta.

Cheliped (Fig. 6 A). Basis attached via indiscrete sclerite, shorter than carpus, naked. Merus with one ventral seta. Carpus longer than propodus including fixed finger, with two ventral and two tiny dorsal setae. Propodus slender twice as long as broad, with one rigid inner seta at dactylus insertion. Fixed finger with two ventral and three setae on inner margin as well as two inner distal denticles. Dactylus as long as fixed finger, naked.

Pereopod 1 (Fig. 6 B). Coxa spherical (not illustrated). Basis longer than the three succeeding articles combined, naked. Ischium with one simple seta. Merus shorter than carpus, widening distally, and with two simple setae. Carpus shorter than half of basis, with one simple and two bayonet setae distally. Propodus with one ventrosubdistal spiniform seta, one simple ventral seta, distal spinules, dorsal seta and spine. Dactylus and unguis combined shorter than propodus, and not fused.

Pereopod 2 (Fig. 6 C). As pereopod 1 except: merus with one bayonet and one simple setae. Carpus with three bayonet setae. Propodus with only ventro-subdistal spiniform and one simple dorso-subdistal setae.

Pereopod 3 (Fig. 6 D). As pereopod 2 except: coxa naked.

Pereopod 4 (Fig. 6 E). Coxa incompletely fused with somite. Basis longer than the three succeeding articles combined, naked. Ischium with two setae. Merus shorter than carpus, widening distally, and with two distal bayonet setae. Carpus shorter than half of basis, with three distal bayonet setae and one bone-shaped seta. Propodus longer than carpus, with three distal bayonet setae and a dorsal spine. Dactylus and unguis combined longer than propodus, not fused.

Pereopod 5 (Fig. 6 F). As pereopod 4 except: basis with two dorsomedial setulose setae.

Pereopod 6 (Fig. 6 G). As pereopod 5 except: basis with one dorsomedial setulose seta. Propodus with four distal bayonet setae and a dorsal spine.

Pleopods not present in female.

Uropod (Fig. 6 H). Longer than pleotelson and last pleonite combined. Basal article naked and as long as endopod. Endopod article 1 with one distal setulose seta; article 2 shorter than article 1, with four long and one short simple distal setae. Exopod reduced to a knob but not fused with basal article, with two simple setae of which one is longer than endopod.

Remarks. This genus is poorly defined and only contains two species, the one described above, P. heardi Larsen, 2005. The new species is unique in possessing a propodal dorsal seta on pereopods 1 to 3. Furthermore, it can easily be separated from P. heardi by the antennule article 3 being wider than long, by the maxilliped endite tubercles and setae, and the palp article 2 with outer seta.