Phylladiorhynchus eneus, 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 : 34-38

Phylladiorhynchus eneus n. sp.

( Figs. 11L , 12 )

Phylladiorhynchus ikedai . — Baba, 1991, 485 (in part only specimens from MUSORSTOM 4, Stn 151 [MNHN Ga-2042] and CALSUB, Pl 18 [MNHN Ga-2047]).

Records requiring verification:

Phylladiorhynchus ikedai . — Baba, 2005: 200, 304 (Kei Islands).

Type material. Holotype. Indonesia. KARUBAR Stn DW 18, 05.3000°S, 133.0167°E, 205–212 m, 24 October 1991: M 3.0 mm (MNHN-IU-2014-13846).

Paratypes. Philippines. MUSORSTOM 2 Stn CP 01, 14.0000°N, 120.3000°E, 188–198 m, 20 November 1980: 1 M 2.1 mm (MNHN-IU-2014-13801) .

Indonesia. KARUBAR Stn DW 18, 05.3000°S, 133.0167°E, 205–212 m, 24 October 1991: 1 F 2.8 mm (MNHN- IU-2016-497).— Stn DW 50, 07.9833°S, 133.0333°E, 184–186 m, 30 October 1991: 1 F 1.7 mm (MNHN-IU-2014- 13850) .

Papua New Guinea. BIOPAPUA Stn DW 3770, 05.5667°S, 51.5333°E, 220–294 m, 16 October 2010: 1 M 2.5 mm (MNHN-IU-2011-2157) .

Other material. New Caledonia. MUSORSTOM 4 Stn DW 151, 19.1167°S, 163.3667°E, 200 m, 14 September 1985: 1 M 2.2 mm (MNHN-IU-2014-23833 (Ga-2042)).—CALSUB Pl 18, 22.7667°S, 167.3333°E, 200–300 m, 29 March 1989: 1 M 2.3 mm (MNHN-IU-2014-23837 (Ga-2047)).— Lagon Nord. Stn DW 1151, 19.0167°S, 163.4500°E, 270–280 m, 28 October 1989: 1 M 3.2 mm (MNHN-IU-2014-13798).—EXBODI Stn CP 3833, 22.0333°S, 167.0667°E, 325–332 m, 8 September 2011: 1 M 2.4 mm (MNHN-IU-2019-2695).—KANACONO Stn CP 4656, 22.6667°S, 167.2000°E, 219–244 m, 10 August 2016: 1 F 2.4 mm (MNHN-IU-2017-11637).— Stn CP 4665, 22.8667°S, 167.3333°E, 535–563 m, 11 August 2016: 1 M 1.9 mm, 2 F 2.4–2.5 mm (MNHN- IU-2017- 3954) .

Etymology. From the name Eneus, an Argonaut, son of Caeneus. The name is considered a substantive in apposition.

Description. Carapace: Moderately robust, 0.9–[1.0] × as long as broad; transverse ridges with dense short setae, and few scattered thick iridescent setae. Gastric region convex (upraised dorsally) with some transverse ridges: epigastric ridge indistinct, with 5 spines (1 median and 2 pairs of spines laterally) followed by median scale behind epigastric ridge, often armed with very long thick plumose setae; anterior protogastric ridge medially interrupted, followed by 1 median scale in posterior protogastric area; anterior mesogastric ridge not medially interrupted, laterally interrupted by anterior branch of cervical groove; anterior metagastric ridge not medially interrupted, and followed by a few scales on posterior metagastric region. Mid-transverse ridge medially depressed, not interrupted, preceded by distinct cervical groove, followed by 2 not interrupted or minutely interrupted ridges, interspersed with 1 short lateral ridge. Lateral margins clearly convex, with 7 spines: first anterolateral spine well-developed, reaching end of lateral orbital spine, second spine (hepatic) small, slightly dorsomesially from lateral margin, and followed by 5 branchial spines (3 anterior and 2 posterior). Rostrum leaf-like, horizontal, dorsally flattish or slightly concave, [1.3]–1.5 × as long as broad, length 0.3–[0.4] and breadth 0.2–[0.3] that of carapace; lateral margins serrated and convex, with well-developed supraocular basal spines, subapical spines minute or obsolescent. Pterygostomian flap ending in anterior spine, upper margin serrated, with series of uprised striae.

Thoracic sternum: As wide as long or slightly wider than long. Sternite 3 moderately broad, [2.5]2.0–3.0 × as wide as long, anterior margin convex with a median deep notch. Sternite 4 widely contiguous to sternite 3; surface depressed in midline, smooth; greatest width 2.6–[2.7] × that of sternite 3, 2.3–[2.6] × as wide as long.

Pleon: Elevated ridges with short setae and a few scattered long setae. Tergites 2–3 with anterior and posterior transverse elevated ridges; tergite 4 with anterior transverse ridge; tergites 5–6 smooth.

Eye: Eyestalk length about 1.2–1.3 × broader than long, peduncle distally setose, not distinctly expanded proximally; maximum corneal diameter 0.75 × rostrum width, as wide as eyestalk.

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

Antenna: Article 1 with prominent mesial process, distally clearly not reaching lateralmost antennular spine. Article 2 with distinct distomesial and distolateral spines. Articles 3 and 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus 0.5–[0.6] × length of ischium, with well-developed distal spine on extensor margin and 2 strong spines on flexor margin.

P1: [3.1]3.0–3.3 (males), 2.8–2.9 (females) × carapace length; subcylindrical, spiny and with dense short setae and scattered long stiff 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, [2.0]–2.7 × as long as carpus. Carpus 1.8–[2.3] × as long as wide. Palm 1.2–[1.3]× carpus length, [2.2]–2.7 × as long as broad with parallel rows of spines running along lateral and mesial margin and scattered spines on dorsal and ventral surfaces. Fingers [0.7]0.7–0.9 × 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 0.8–[1.0] × length of P2 merus, P4 merus [lost in holotype]0.9 × length of P3 merus. P2 merus, [0.7]–0.8 × carapace length, 4.9–[5.0] × as long as broad, 1.1–[1.2] × as long as P2 propodus; P3 merus [6.0]–7.0 × as long as broad, [1.1]–1.3 × as long as P3 propodus; P4 merus 7.0 × as long as broad, 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 4 small spines, absent in P2–3. Carpi with 2 or 3 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 margins of all P2–4 irregular, each with distal spine. Propodi slender, [7.5–8.5]7.0–10.0 × as long as broad; extensor margin irregular, usually unarmed; flexor margin with 3–4 slender movable spines in addition to distal pair. Dactyli [0.7]–0.8 × length of propodi, ending in incurved, strong, sharp spine; flexor margin with 6–7 movable spines.

Eggs: No data.

Live colour. Unknown.

Genetic data. COI, mini-barcode fragment (158 bp).

Distribution. Philippines, Indonesia, Papua New Guinea and New Caledonia, from 184 to 563 m.

Remarks. Phylladiorhynchus eneus belongs to the group of species having the epigastric ridge with 5 spines, 3 spines on the anterior branchial margin of the carapace and the Mxp3 merus with 2 prominent spines along the flexor margin. This group contains the following species: P. acastus from the Philippines, Papua New Guinea, Vanuatu, Chesterfield Islands and New Caledonia, P. argus , from French Polynesia, New Caledonia and Chesterfield Islands, P. paula , from the southwestern Indian Ocean, and P. erebus Schnabel & Ahyong, 2019 from Norfolk and Kermadec Ridges. However, the new species can be distinguished from the other species of the group by the following characters:

- One median scale behind the median epigastric spine in P. eneus , whereas this scale is absent in the other species.

- The anterior protogastric ridge is medially interrupted or scale-like in P. eneus , whereas this ridge is not interrupted in the other species.

- The P2–4 propodi are more slender (7–10 × longer than wide) in P. eneus , whereas these propodi are 4–7 × longer than wide in the other species.

- The anterior margin of the pterygostomian flap is serrated margin in P. eneus whereas smooth in the other species.

The specimens of P. eneus range in size range from 1.9 to 3.2 mm postorbital carapace length. The genetic divergences between P. eneus and other species were always higher than 18% (COI, based on the 158 bp minibarcode). The two sequences of P. eneus from New Caledonia diverged by 0.6%.

Figures

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.

FIGURE 12. Phylladiorhynchus eneus n. sp., holotype male 3.0 mm (MNHN-IU-2014-13846): 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, right P1, dorsal view. F, left P2, lateral view. G, right P3, lateral view. H, dactylus of left P2, lateral view. Scale bar: A, E–G = 1.0 mm; B–D, H = 0.6 mm.