Phylladiorhynchus lynceus, 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 : 83-85

Phylladiorhynchus lynceus n. sp.

( Figs. 31 , 33C , 37E–F )

Type material. Holotype. Chagos Archipelago , Great Chagos Bank , Brothers Island. Stn CH 0614 dead branching coral heads. Outer Reef Slope, 8–12 m, February 2012: ov. F 2.0 mm (MNHN-IU-2019-2593)

Paratypes. Chagos Archipelago , Great Chagos Bank , Eagle Island . Stn CH 1364 dead branching coral heads. Outer Reef Slope , 8–12 m, February 2012: 1 ov. F 1.4 mm, 1 F 1.3 mm (MNHN-IU-2019-2594).— Stn CH 0447, 1 M 1.7 mm ( OUMNH. ZC.2014-09-064).— Stn CH 0230, 1 M 1.2 mm ( OUMNH. ZC.2014-09-065) .

Kiribati. Line Islands. 9.91°S, 150.21°W, 11 m, 8 November 2013: 1 M 1.9 mm ( UF41803 ).— Millenium island . 9.91°S, 150.21°W, 12 m, 5 November 2013: 1 M 1.8 mm 1 ov. F 1.3 mm ( UF40895 ) .

Other material. American Samoa, Olosega Island. Stn OLO-187, 14.18140174°S, 169.6267462°W, 14 m, 14 March 2015: 1 M 1.8 mm ( UF54480 ) .— Stn OLO-094, 14.18140174°S, 169.6267462°W, 14 m, 14 March 2015: 1 ov. F 2.1 mm ( UF54481 ) .— Rose Atoll. Stn ROS-610, 14.54895°S, 168.13792°W, 15 m, 17 March 2015: 8 M 1.4– 2.1 mm, 8 ov. F 1.5–2.3 mm ( UF54482 ) .— Stn ROS-527, 14.54895°S, 168.13792°W, 15 m, 17 March 2015: 1 M 1.9 mm, 1 ov. F 1.8 mm ( UF54483 ) .— Stn ROS-562, 14.54895°S, 168.13792°W, 15 m, 17 March 2015: 10 M 1.4–2.1 mm, 13 ov. F 1.4–2.1 mm, 2 F 1.5–1.8 mm ( UF54484 ) .— Ofu Island . Stn OFU-121, 14.17765914°S, 169.649504°W, 14 m, 21 March 2015: 1 ov. F 2.3 mm ( UF54477 ) .— Stn OFU-168, 14.17765914°S, 169.649504°W, 14 m, 21 March 2015: 1 M 1.9 mm, 1 ov. F, 2.2 mm ( UF54478 ) .— Stn OFU-280, 14.18628°S, 169.6599°W, 14 m, 26 March 2015: 1 M 1.8 mm, 1 ov. F 1.9 mm ( UF54479 ) .

Kiribati. Phoenix islands, Orona island . 4.519°S 172.227°W, 12 m, 17 September 2015: 1 ov. F 1.7 mm ( UF51296 ) .— 4.520°S, 172.230°W, 15 m, 18 September 2015: 1 M 1.5 mm ( UF51370 ) , 2 M 1.8–1.9 mm 1 ov. F 1.8 mm ( UF51363 ) .— Nikumaroro Island . 4.656°S, 174.545°W, 14 m, 23 September 2015: 1 ov. F 1.7 mm ( UF51559 ) .— 4.694° S 174.490°E, 7.5–9 m, 25 September 2015: 1 M 1.3 mm ( UF51644 ) .

Western Australia. Hibernia Reef. Stn 142/K13, 11°59.292’S, 123°21.154’E, no depth, 4 October 2013: 1 M 2.1 mm ( WAM C55689) .— Rowley Shoals. Mermaid Reef. Stn 178/K14-T1, 17°09.69’S, 119°38.826’E, 12–18 m, 13 October 2014: 1 ov. F 1.6 mm ( WAM C53889) .

Etymology. From the name Lynceus, an Argonaut, son of Aphareus and Arene. 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 long and thick iridiscent setae. Gastric region slightly convex with 4 transverse ridges: epigastric ridge distinct with 2 spines ( Samoa and Kiribati specimens often with 1 median produced scale usually with thick plumose setae before epigastric ridge), short scales laterally; anterior protogastric ridge not medially interrupted, nearly extending laterally to carapace margin; anterior mesogastric ridge not medially interrupted, laterally continuing to first branchial spine; sometimes followed by some short small scales; anterior metagastric ridge medially interrupted, laterally continuing to second branchial spine. Mid-transverse ridge not interrupted, cervical groove indistinct, followed by 2 not interrupted or minutely interrupted ridges, interspersed with 1 short lateral ridge and sometimes few, short scattered scales. Lateral margins slightly convex, with 4 distinct spines: first anterolateral spine welldeveloped, reaching anteriorly to level of lateral orbital spine, hepatic margin unarmed; anterolateral spine followed by 3 branchial spines (2 anterior and 1 posterior spines). Rostrum leaf-like, horizontal, dorsally concave, [1.5]–1.6 × 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 and small subapical spines. Pterygostomian flap ending in blunt tooth, upper margin smooth.

Thoracic sternum: As wide as long. Sternite 3 quadrangular, slightly wider than long (1.5 × as wide as long), anterior margin with median blunted projection, lateral margins rounded. Sternite 4 widely contiguous to sternite 3; surface depressed in midline, smooth; greatest width 3.0 × that of sternite 3, [2.7]2.5–3.0 × as wide as long.

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

Eye: Eyestalk length about 0.9–[1.0] × broader than long, peduncle distally setose, slightly expanded proximally; maximum corneal diameter 0.8–[0.9] × rostrum width, narrower than eyestalk (0.8 × maximum peduncle width).

Antennule: Article 1 slightly longer than wide, with 5 distal 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 well-developed distomesial and distolateral spines. Article 3 with distomesial spine. Article 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus 0.6–[0.8] × length of ischium, with distal spine on extensor and flexor margins.

P1: 1.7–2.0 (males), 2.0 (females) × carapace length; subcylindrical, spiny and with dense long stiff setae; merus, carpus and palm with spines along mesial, dorsal and lateral surfaces, distal and mesial spines usually stronger than others. Merus 0.7–0.8 length of carapace, 2.0–2.1 × as long as carpus. Carpus 1.2–1.3 × as long as wide. Palm 1.2–1.3 × carpus length, 1.5–1.7 × as long as broad. Fingers unarmed, 0.6–0.9 × palm length.

P2–4: Stout, setose and spinose. Meri successively shorter posteriorly: P3 merus 0.7–[0.8] × length of P2 merus, P4 merus 0.8 × length of P3 merus. P2 merus, 0.7–[0.8] × carapace length, [3.6]–3.8 × as long as broad, [1.2]–1.3 × as long as P2 propodus; P3 merus 3.7 × as long as broad, [1.0]–1.1 × as long as P3 propodus; P4 merus [2.8]2.7–3.2 × as long as broad, [1.0]–1.1 × 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, unarmed; flexor margin irregular,with distal spine on P2–3, unarmed on P4. Carpi with 1–3 prominent spines on extensor margin on P2–3, unarmed on P4; distal spine prominent on P2–3, smaller on P4; row of small spines or granules below extensor margin on lateral surface of P2–3, unarmed on P4; flexor margin unarmed. Propodi stout, [3.8]3.3–4.3 × as long as broad; extensor margin irregular, armed with 1–3 spines on proximal half or 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 4–6 movable spines.

Eggs: Ov. F carried approximately 5– 25 eggs of 0.3–0.4 mm diameter.

Live colour. Unknown.

Genetic data. COI and 16S, Table 1.

Distribution. Chagos Archipelago, Western Australia, Kiribati, American Samoa, between 7.5 and 18 m.

Remarks. Phylladiorhynchus lynceus belongs to the group of species with 2 epigastric spines and 2 spines on the anterior branchial margin. The closest species are: P. integrirostris , from Hawaii and P. priasus from the Mariana and Marshall Islands. The three species are barely distinguishable morphologically, although they are genetically very different (see the differences under the Remarks of P. priasus ). Furthermore, these three species are also close to P. orpheus (see the differences under the Remarks of P. orpheus ).

The specimens of P. lynceus range from 1.2 to 2.3 mm postorbital carapace length. The four and seven sequences of P. lynceus from American Samoa and Chagos and Kiribati diverged 1.0–2.3% (COI) and 0–1% (16S), respectively.

Figures

FIGURE 31. Phylladiorhynchus lynceus n. sp., holotype ovigerous female 2.0 mm (MNHN-IU-2019-2593): 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, left 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 33. Rostrum, dorsal view. A, Phylladiorhynchus laureae n. sp., paratype female 1.7 mm (MNHN-IU-2019-2635). B, P. lini n. sp., holotype female 2.2 mm. C, P. lynceus n. sp., holotype ovigerous female 2.0 mm (MNHN-IU-2019-2593). D, P. marina n. sp., male 1.5 mm (MNHN-IU-2019-2653). E, P. medea n. sp., paratype male 2.1 mm (MNHN-IU-2014-13795). F, P. nudus Macpherson, 2008, ovigerous female 2.4 mm (WAM C46587). G, P. nui Schnabel & Ahyong, 2019, male 6.5 mm (MNHN-IU-2019-2595). H, P. orpheus n. sp., paratype male 1.9 mm (UF33962). I, P. paula n. sp., paratype male 2.3 mm (MNHN-IU-2019-2699). J, P. penelos n. sp., paratype male 3.3 mm (UF1224). K, P. pepei n. sp., holotype male 3,2 mm (MNHN-IU-2016-486). L, P. phanus n. sp., paratype male 2.1 mm (MNHN-IU-2019-2687). Scale bars = 1 mm.

FIGURE 37. A, C, E, Carapace, dorsal view; B, D, F, rostrum, dorsal view.A-B, Phylladiorhynchus integrirostris (Dana, 1852), male 2.0 mm (UF54544). C-D, Phylladiorhynchus priasus n. sp., paratype male 2.0 mm (UF54475). E-F, Phylladiorhynchus lynceus n. sp., paratype male 1.8 mm (UF54479). Scale bars: A, C, E = 1 mm; B, D, F = 0.5 mm.