Neaxius capricornicus, Poore & Dworschak, 2018

Poore, Gary C. B. & Dworschak, Peter C., 2018, The Indo-West Pacific species of Neaxiopsis and Neaxius (Crustacea: Axiidea: Strahlaxiidae), Memoirs of Museum Victoria (Mem. Mus. Vic.) 77, pp. 15-28 : 21-24

Neaxius capricornicus sp. nov.

(http://zoobank.org/urn:lsid:zoobank.org:act:0FEDB7A0-7265-

4E5B-A26D-861FFFB7F7B6)

Figures 6 , 8g –l

Axius (Neaxius) glyptocercus .— Poore and Griffin, 1979: 236–238 (partim), figs 8g –i.

Neaxius glyptocercus .— Tudge and Cunningham, 2002: 841.— Tsang et al., 2008: 218–219.— Robles et al., 2009: 316.— Sakai, 2011: 326–331 (partim) figs 62A, B, E.

Material examined. Holotype. Australia, Qld, North Stradbroke I., Deanbilla Bay, Dunwich, 27° 30' S, 153° 24' E, NMV J39643 (female, 26 mm; see Tudge and Cunningham [2002]),

Paratypes. Collected with holotype. NMV J71641 (female, 23 mm); NMV J40714 (2 females, 26 mm; male, 21 mm) .

Australia, Qld , North Stradbroke I., Dunwich, 27° 30' S, 153° 24' E, AM P.13723 (male, 27 mm). Capricorn Group, North West I., 23° 18' S, 151° 42' E, AM P.10060 (female, 38 mm), AM P.11829 (female, 30 mm) .

Other material. Fiji, Viti Levu, ZMH K8392 (Godeffroy No. 7430) ( Sakai, 2011: fig. 62A, E) (male, 14.3 mm).

French Polynesia, Tahiti. ZMH 41226 ( Sakai, 2011: fig. 62B) (male, 27 mm).

Diagnosis. Carapace supra-antennal margin with anteriorly directed spine; anterolateral margin with 6 (5–7) spines, dorsalmost anterolaterally directed; branchiostegite anterior margin with 1 spine; cervical groove without spines along posterior margin. Telson 1.3–1.5 times as wide as long; tapering from widest point to posterior margin; anterior transverse ridge straight, curving laterally to reach lateral margin at its widest point; posterior transverse ridge situated at 0.5 distance between first transverse ridge and posterior margin, ends sharply rounded, almost overhanging; lateral margin with 0–2 marginal teeth; posterior face concave, with shallow median groove, smooth sublaterally. Antenna article 2 without upper-mesial spine, without lateral spine; scaphocerite with 1 mesial sharp spine, 2 (1–4) sharp ventral spines; article 4 lower margin without spines. Cheliped merus, lower margin with 5 (4–6) spines, distolateral face with row of 4 (3–5) spines. Pereopod 2 merus, lower margin with 6 (3–11) spines. Pereopod 3 merus, lower margin with 8 (4–12) spines.

Supplementary description of holotype. Rostrum with 5 pairs of erect blunt spines; sharp hiatus before smooth lateral carina; median carina with 5 tubercles; anterior gastric region rugose; cervical groove defined posteriorly by sharp carina; branchiostegal groove separating smooth cardiac region from punctate branchiostegal region. Anterolateral margin with 6 spines on right, 5 on left, first flaring laterally, longer gap between third and fourth, between fifth and sixth; anterior branchiostegal margin with 1 short spine. Pleomere 1 pleuron with 3 tubercles; pleomere 2 with 7 tubercles. Telson 1.35 times as wide as long; widest at prominent lateral lobes, at c. 0.4 of length; tapering sharply then gradually from widest point to posterior margin; posterior margin c. 0.6 times greatest width; anterior transverse ridge at c. 0.25 length, straight, curving laterally to reach lateral margin at its widest point; posterior transverse ridge situated at 0.5 distance between first transverse ridge and posterior margin, ends sharply rounded, almost overhanging; lateral margin without marginal teeth; posterior face concave, with shallow median groove, smooth sublaterally. Antenna article 2 without mesial spine, without lateral spine; scaphocerite with 1 mesial sharp spine, 3 sharp ventral spines; article 4 lower margin without spines. Maxilliped 3 merus with 1 short, 2 longer distal spines. Cheliped coxa with 2 spines; basis with 1 spine; ischium with 3 spines; merus, lower margin with 4 spines on right, 5 on left, distolateral face with row of 3 spines, upper margin with 4 spines; carpus lower margin with 1 distal spine. Pereopod 2 coxa with 2 spines; basis with 2 spines; ischium with 3 spines; merus, lower margin with 7 spines on right, 6 on left, more proximal one minute. Pereopod 3 coxa with 2 spines; basis with 2 spines; ischium without spines; merus, lower margin spines in 2 rows: 6 spines mesially, last 3 minute, 6 laterally, last minute. Pereopods 4 and 5 without spines.

Etymology. For the Tropic of Capricorn, which marks the species’ northern limit in Queensland, Australia. The name is a noun in apposition.

Distribution. Australia, Queensland, 23°S – 27° 30' S; Fiji; French Polynesia.

Remarks. Neaxius capricornicus and N. glyptocercus are immediately differentiated from N. acanthus in having a prominent supra-antennal spine on the anterior margin of the carapace, and both the cervical groove and second antenna article unarmed. Neaxius capricornicus differs from N. glyptocercus in having: 2–4 spines on the lower margin of the scaphocerite (vs. usually none, rarely 1 or 2 in N. glyptocercus ), 3–5 spines along the distolateral ridge of the merus of the cheliped (vs. usually none, rarely one), 3–11 spines on the lower margin of the merus of pereopod 2 (vs. none), 8–12 (rarely fewer) spines on the lower margin of the merus of pereopod 3 (vs. none), one spine on the anterior margin of the branchiostegite (vs. 2 or 3) and the dorsalmost spine of the anterolateral carapace margin directed anterolaterally (vs. anteriorly).

The two species were confused by Poore and Griffin (1979) who illustrated both in their fig. 8.

Specimens from Fiji ( ZMH K8392; Sakai, 2011: fig. 62A, E) and Tahiti ( ZMH K41226 ; Sakai, fig. 62B) have 2 spines on the lower margin of the scaphocerite, 4 and 3 spines respectively along the distolateral ridge of peropod 1 merus, 4 and 10 spines respectively on the lower margin of pereopod 2, 8 and 10 spines respectively on the lower border of pereopod 3 merus and 1 spine on the anterior margin of the branchiostegite, within the range of the Australian material.

Figures

Figure 6. Neaxius capricornicus sp. nov., holotype, NMV J39643: a, lateral carapace, merus of cheliped; b, anterior carapace; c, telson; d, telson, right uropod; e, f, pereopods 2, 3. Paratype, NMV J71643: g, pereopod 4; h, habitus lateral; i, dorsal carapace j, telson and uropods. All pereopods, lateral faces. Scale bars = 5 mm.

Figure 8. Neaxius acanthus (A. Milne-Edwards, 1879), NMV J17235, male, 26 mm: a–f. Neaxius capricornicus sp. nov., holotype, NMV J39643: g–k. Paratype, NMV J71641: l. Neaxius glyptocercus (von Martens, 1868), AM P.16177: m–r. Note: a, b, g, h, m, n, dorsal and lateral views of anterior carapace; c–f, i–l, o–r, pereopods 1–4. Pereopods 1, 2 in lateral view, pereopods 3, 4 in mesial view. Scale bar = 5 mm.