Platyaxius bardi, Poore & Collins, 2009

Poore, Gary C. B. & Collins, David J., 2009, Australian Axiidae (Crustacea: Decapoda: Axiidea), Memoirs of Museum Victoria 66 (2), pp. 221-287 : 274-277

Platyaxius bardi sp. nov.

Figures 35 , 36 , 47

Material examined. Holotype. WA, near Mermaid Reef, 17°29.23'S, 120°27.64'E – 17°29.72'S, 120°28.07'E (stn SS05-2007 091), 187– 184 m, 20 Jun 2007, NMV J55707 (male, cl. 5.9 mm, tl. 17.2 mm).

Paratypes. WA, North-west Shelf , between Port Hedland and Dampier, 18°36'S, 118°02'E – 18°39'S, 118°04'E (stn NWA-24), 184 m, 06 Jun 1983, NMV J15420 (2 ovigerous females, cl. 5.7 mm) .

Description of male holotype. Carapace smooth. Rostrum 0.3 times length of front-to-cervical groove, narrowly triangular, with 4 weak lateral spines anterior to supraocular spine, continuous with definite lateral gastric carinae. Supraocular spines similar size to other rostrum spines. Lateral gastric carina with 2 prominent spines in addition to supraocular spine. Submedian gastric carina with 4 spines. Median gastric carina with 6 spines. Sternite 7 (pereopod 4) deeply divided in midline over posterior two-thirds and with sharp oblique lateral ridge. Sternite 8 (pereopod 5) with setose semicircular flap on anterior face at base of leg. Abdominal pleuron 1, 2.6 times as deep as middorsal length, ventrally acute; pleuron 2 asymmetrical, lateral length 1.2 times dorsal length, posteroventrally quadrate; pleura 3–5 posteroventrally angled, each with small anteroventral spine; pleuron 6 with small spine on ventral margin.

Eyestalk 0.8 length of rostrum; cornea pigmented.

Antennular peduncle reaching to distal part of antennal article 4. Antennal article 1 with 2 spinules on lower distal margin; article 2 distal spine well developed, reaching to proximal part of antennal article 5; scaphocerite strongly curved downwards, reaching distally almost to end of article 4; article 3 with spine on lower margin; article 4 approximately as long as article 2 (excluding distal spine); article 5 about two-thirds length of article 4. Maxilliped 3 basis with 1 spine; ischium with 1 spine on lower margin; crista dentata with numerous small, even teeth; merus with 3 spines on lower margin; carpus unarmed.

Pereopods 1 differentiated, propodus of major cheliped longer and more swollen than minor. Major pereopod 1 (left) coxa lower margin with 1 spine; basis lower margin unarmed; ischium lower margin with 4 small spines and 1 larger; merus upper margin strongly convex, unarmed, lower margin with 10 teeth, lateral face smooth, mesial face smooth; carpus upper margin carinate, lower margin unarmed, lateral face smooth, mesial face smooth; propodus upper margin carinate, with blunt distal tooth, lower margin with weak lateral carina, better defined on finger, lateral face tuberculate over upper and lower distal third, mesial face tuberculate near base of finger; fixed finger 0.6 length of upper palm, cutting edge straight,; dactylus margins and faces smooth, cutting edge with few blunt teeth.

Minor pereopod 1 coxa, ischium, merus and carpus as in larger cheliped, narrower; propodus upper margin carinate, with blunt distal tooth, lower margin with weak lateral carina, better defined on finger, lateral face with few tubercles, mesial face with few tubercles near base of finger; fixed finger as long as upper palm, cutting edge with regularly spaced sharp teeth; dactylus margins and faces smooth, cutting edge denticulate.

Pereopod 2 ischium lower margin unarmed; merus lower margin unarmed; carpus slightly longer than chela; propodus upper margin 0.4 length of dactylus. Pereopod 3 merus lower margin with 3 weak spines; propodus 2.9 times as long as dactylus, with 8 transverse rows each of 4–7 robust setae; dactylus with 13 robust setae on inner face plus unguis. Pereopod 4 propodus 4.1 times as long as dactylus, with 8 transverse rows each of 3–8 robust setae; dactylus with 12 robust setae on inner face plus unguis. Pereopod 5 propodus 3.5 times as long as dactylus, weakly subchelate, distally with 2 transverse rows each of 2 or 3 robust setae; dactylus with 6 robust setae on distal margin, 3 robust setae on inner face.

Pleopods 2–5 appendix interna one third length of endopod. Pleopod 2 appendix masculina as long as appendix interna.

Telson ovate, slightly tapering posteriorly, 1.1 times as long as wide, lateral margin with 3 spines, distal margin convex with posteromedian spine, posterolateral curve with 1 robust seta; dorsal face with 2 spines in each oblique row. Uropodal endopod 1.7 times as long as wide, with 7 lateral spines, longitudinal ridge with 4 spines (including marginal). Uropodal exopod 1.6 times as long as wide, with 11 lateral spines, 2 longitudinal ribs (inner rib ending in marginal spine, outer rib with 7 spines), posterolateral angle with 1 fixed spine and 1 robust seta; transverse suture absent.

Female (2 paratypes). As male except: rostrum with 4–6 lateral spines anterior to supraocular spine; lateral gastric carina with 2 or 3 prominent spines in addition to supraocular spine; submedian gastric carina with 4 or 5 spines; median gastric carina with 5–7 spines; pleura 3–5 posteroventrally angled, each with small anteroventral spine (as male); pleuron 6 with small spine on ventral margin; major and minor chelipeds fixed finger and dactylus with lateral ridge; pleopod 1 uniramous, article 2, 3 times length of article 1; ovigerous with at least 6 eggs.

Etymology. Bardi is the name of the Aboriginal Australian people inhabiting Cape Leveque close to the type locality (noun in apposition).

Distribution. WA, continental slope of North-west Shelf, 17°– 19°S, 118°– 120°E, 180–184 m depth.

Remarks. The three individuals of Platyaxius bardi vary in the numbers and size of spines/teeth on the rostrum and gastric carinae. The species differs from P. brevirostris and P. odontorhynchus (from Indonesia) in the more pronounced dentition on the rostrum and gastric carina (obsolete in the other two). The rostrum exceeds the eyestalks in the new species (does not in the other two species) and uropodal rami are broader. The scaphocerite of P. bardi is strongly curved while it is straight in the other two species. Platyaxius bardi and P. brevirostris have both been taken from similar limited latitudes and depths on the north-western Australian shelf. Platyaxius bardi has teeth on the lateral gastric carina while P. brevirostris does not.

Figures

Figure 35. Platyaxius bardi sp. nov. a, lateral view. b, dorsal view of carapace, peduncles of antennule and antenna. c, thoracic sternites 6–8. d, telson and right uropod. e, major pereopod 1 (left, lateral). f, minor pereopod 1 (right, lateral). All figures from holotype.

Figure 36. Platyaxius bardi sp. nov. a, maxilliped 3. b–e, pereopods 2–5 (b, e right; c, d left; each with details of dactylus). f, male pleopod 2. All figures from holotype.

Figure 47. Platyaxius bardi sp. nov. Photomicrographs of (left to right) maxilla 1, maxilla 2 (posterior epipod seta missing), maxilliped 1, maxilliped 2.