Phylladiorhynchus argus, Rodríguez-Flores & Macpherson & Machordom, 2021

Rodríguez-Flores, Paula C., Macpherson, Enrique & Machordom, Annie, 2021, Revision of the squat lobsters of the genus Phylladiorhynchus Baba, 1969 (Crustacea, Decapoda, Galatheidae) with the description of 41 new species, Zootaxa 5008 (1), pp. 1-159 : 16-17

Phylladiorhynchus argus n. sp.

( Fig. 4 , 11D )

Phylladiorhynchus ikedai . — Baba, 1991: 485 fig. 4a, b (in part, only material from MUSORSTORM 4, Stn 238 [MNHN Ga- 2043], MUSORSTORM 6, Stn DW485 [MNHN Ga-2045] and CALSUB, Pl 16 [MNHN Ga-2046]).

Type material. Holotype. New Caledonia. EXBODI Stn DW 3785, 22.2500°S, 167.1667°E, 386–387 m, 02 September 2011: M 2.5 mm (MNHN-IU-2011-7659).

Paratypes. New Caledonia. MUSORSTOM 4 Stn CP 238, 22.2167°S, 167.2333°E, 500–510 m, 2 October 1985: 1 ov. F 3.5 mm (MNHN-IU-2014-23836 (Ga-2043)).—MUSORSTOM 6 Stn DW 485, 21.3913°S, 167.9883°E, 380 m, 23 February 1989: 1 F 3.2 mm (MNHN-IU-2014-23835 (Ga-2045)).—CALSUB Pl 16, 20.6300°S, 167.0450°E, 500 m, 7 March 1989: 1 M 3.2 mm (MNHN-IU-2013-19941 (Ga-2046)) .

Other material. New Caledonia. KANACONO Stn DW 4778, 23.0500°S, 168.3000°E, 170–248 m, 28 August 2016: 1 M 2.9 mm (MNHN-IU-2016-488) .

Chesterfield Islands . KANADEEP Stn CP 4985, 20.8167°S, 160.9500°E, 480–540 m, 10 September 2017: 1 M 3.0 mm (MNHN-IU-2017-3138) .

French Polynesia. BENTHAUS Stn DW 2006, 22.4500°S, 151.3167°W, 350–450 m, 24 November 2002: 1 M 3.4 mm (MNHN-IU-2014-13883) .

Etymology. From the name Argus, an Argonaut, son of Phrixus; builder of the boat Argo. The name is considered a substantive in apposition.

Description. Carapace: As long as or slightly longer than broad; transverse ridges with dense short setae, and few scattered thick setae. Gastric region flattened with some transverse ridges: epigastric ridge indistinct, with 5 spines (1 median and 2 pairs of spines laterally); anterior protogastric ridge not medially interrupted, nearly extending laterally to carapace margin; anterior mesogastric ridge widely or minutely interrupted, laterally interrupted by anterior branch of cervical groove, continuing to first branchial spine; anterior metagastric ridge scale-like. Mid-transverse ridge not interrupted, medially depressed, preceded by distinct cervical groove, followed by 2 not interrupted or minutely interrupted ridges, interspersed with 1 short lateral ridge and few, short scattered scales. Lateral margins slightly convex, with 7 spines: first anterolateral spine well-developed, reaching end of lateral orbital spine, second spine (hepatic) small to well-developed, slightly dorsomesially from lateral margin, and followed by 5 branchial spines (3 anterior well-developed subequal branchial spines and 2 well developed posterior branchial spines decreasing in size posteriorly). Rostrum triangular, horizontal, dorsally flattish or slightly concave, [1.5]1.2–1.6 × as long as broad, length [0.35]0.3–0.4 and breadth [0.25]0.2–0.3 that of carapace; lateral margins smooth and straight, with well-developed supraocular basal spines, subapical spines absent. Pterygostomian flap ending in blunt tooth, upper margin smooth.

Thoracic sternum: About as wide as long. Sternite 3 sharply broad, [4.0]–4.2 × as wide as long, anterior margin convex with a median deep notch flanked by 2 lobes. Sternite 4 widely contiguous to sternite 3; surface depressed in midline, smooth; greatest width 2.3–[2.6] × that of sternite 3, [2.6]–2.8 × as wide as long.

Pleon: Transverse ridges with short setae and scattered few setae. Tergite 2 with anterior and posterior transverse elevated ridges; tergites 3 and 4 with anterior transverse ridge; tergites 5–6 smooth.

Eye: Eyestalk length about [1.2] × broader than long, peduncle distally setose, not distinctly expanded proximally; maximum corneal diameter [1.2] × rostrum width, as wide as eyestalk.

Antennule: Article 1 1.5 × longer than wide, with 5 spines: distomesial spine small; proximal lateral spine small, always present.

Antenna: Article 1 with prominent mesial process, distally falling well short of lateralmost antennular spine. Article 2 with distinct distal spines laterally and mesially. Articles 3 and 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus 0.6 × length of ischium, with well-developed distal spine on extensor margin and 2 strong spines on flexor margin.

P1: [3.1]3.5 (males), 2.8 (females) × carapace length; subcylindrical, spiny and with scattered long stiff setae and few plumose setae; merus, carpus and palm with spines along mesial, dorsal and lateral surfaces, distal and mesial spines usually stronger than others. Merus [1.2]1.1–1.3 length of carapace, 1.7–[2.5] × as long as carpus. Carpus [2.0]–3.0 × as long as wide. Palm [1.4]1.1–1.5 × carpus length, [1.8]1.6–2.0 × as long as broad. Fingers 0.7–[1.0] × palm length; fixed finger unarmed; movable finger with well-developed basal spine.

P2–4: Slender, subcylindrical, moderately setose and spinose. Meri successively shorter posteriorly: P3 merus 0.7–[0.8]times length of P2 merus, P4 merus [0.7]–0.8 × length of P3 merus. P2 merus, [0.8] or as long as carapace length, [5.5]–7.4 × as long as broad, [1.3]–1.6 × as long as P2 propodus; P3 merus [6.0]–6.2 × as long as broad, [1.3]–1.4 × as long as P3 propodus; P4 merus [4.5]–5.9 × as long as broad, [1.0]–1.3 × as long as P4 propodus; extensor margin of P2 and P3 with row of spines, proximally diminishing, with prominent distal spine; P4 extensor margin irregular with small distal spine; flexor margins of P2–4 irregular, each with distal spine; P4 lateral surface with median row of 3 small spines, absent in P2–3. Carpi with 3 or 4 spines on extensor margin on P2–3, unarmed on P4; distal spine prominent on P2–3, smaller on P4; row of small spines below extensor margin on lateral surface of P2–3, unarmed on P4; flexor margin unarmed. Propodi slender, [6.1–7.0]6.1–7.8 × as long as broad; extensor margin irregular, usually unarmed or armed with proximal spine on P2–3; flexor margin with 2–4 slender movable spines in addition to distal pair. Dactyli [0.6–0.7]0.6–0.7 × length of propodi, ending in incurved, strong, sharp spine; flexor margin with 7–8 movable spines.

Eggs: Ov. F (MNHN-IU-2014-23836) 12 eggs of 0.3–0.4 mm diameter.

Live colour. Unknown.

Genetic data. COI and 16S, Table 1.

Distribution. French Polynesia, New Caledonia and Chesterfield Islands from 170 to 510 m.

Remarks. Phylladiorhynchus argus belongs to the group of species that has 5 epigastric spines, the rostrum margin straight, the subapical spines of the rostrum absent, 3 spines on the anterior branchial margin, and the Mxp3 merus with two prominent spines along the flexor margin. The specimens range from 2.9 to 3.5 mm postorbital carapace length. Phylladiorhynchus argus closely resembles P. acastus from Philippines, Papua New Guinea, Vanuatu, Chesterfield Islands and New Caledonia, and P. paula , from southwestern Indian Ocean (see the differences under the Remarks of P. paula ).

Figures

FIGURE 4. Phylladiorhynchus argus n. sp., holotype male 2.5 mm (MNHN-IU-2011-7659): A, carapace and pleon, dorsal view. B, thoracic sternites 3 and 4. C, left cephalic region, showing antennular and antennal peduncles, ventral view. D, right Mxp3, lateral view. E, left P1, dorsal view. F, right P2, lateral view. G, right P3, lateral view. H, right P4, lateral view. I, dactylus of right P2, lateral view. Scale bar: A, E–H = 1.0 mm; B–D, I = 0.6 mm.

FIGURE 11. Rostrum, dorsal view. A, Phylladiorhynchus acastus n. sp., paratype male 2.6 mm (MNHN-IU-2017-2646). B, P. amphion n. sp., holotype male 2.4 mm (WAM C55691). C, P. amphion n. sp., paratype female 2.6 mm (WAM C53887). D, P. argus n. sp., paratype ovigerous female 3.5 mm (MNHN-IU-2014-23836). E, P. asclepius n. sp., paratype ovigerous female 2.1 mm (UF22401). F, P. australis Schnabel & Ahyong, 2019, female 4.0 mm (MNHN-IU-2019-2596). G, P. bahamut n. sp., holotype male 2.5 mm (UF40205). H, P. barbeae n. sp., paratype male 2.2 mm (MNHN-IU-2019-2643). I, P. boucheti n. sp., paratype ovigerous female 2.5 mm (MNHN-IU-2017-3830). J, P. butes n. sp., paratype female 2.1 mm (MNHN-IU-2016-449). K, P. cepheus n. sp., paratype male 2.4 mm (MNHN-IU-2014-13858). L, P. eneus n. sp., paratype male 2.1 mm (MNHN-IU- 2014-13801). Scale bars = 1 mm.