Phylladiorhynchus pulchrus, 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 : 123-126

Phylladiorhynchus pulchrus n. sp.

( Figs. 47 , 50F )

Type material. Holotype. French Polynesia, MUSORSTOM 9 Stn CP 1156, 07.9833°S, 140.7283°W, 80 m, 23 August 1997: M 1.6 mm (MNHN-IU-2014-13849).

Paratypes. Philippines. MUSORSTOM 3 Stn DR 117, 12.5166°N, 120.6500°E, 92–97 m, 3 June 1985: 1 M 1.4–1.8 mm, 2 ov. F 1.8–2.0 mm (MNHN-IU-2014-13848), 1 M 1.4 mm (MNHN-IU-2017-1342) .

Vanuatu. SANTO Stn DS 103, 15.5683°S, 167.2666°E, 10–80 m, 14 October 2006: 1 M 1.5 mm (MNHN-IU- 2014-13868) .

French Polynesia. MUSORSTOM 9 Stn CP 1239, 09.7033°S, 139.0600°W, 89–95 m, 31 August 1997: 1 ov. F 2.0 mm (MNHN-IU-2014-13733).—no station data: 1 M 1.8 mm (MNHN-IU-2019-2675) .

Etymology. From the latin pulcher, beautiful, in reference to the beauty of this species.

Description. Carapace: Robust or massive, [0.9]–1.1 × as long as broad; transverse ridges elevated, serrated, with few short setae, and few scattered long 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); anterior protogastric ridge not medially interrupted, laterally interrupted with few scales to carapace margin, posterior protogastric ridge scale-like; anterior mesogastric ridge scale-like, laterally interrupted by anterior branch of cervical groove, laterally continuing with some scales; anterior metagastric ridge scale-like, followed by some scales on posterior metagastric area. Mid-transverse ridge not interrupted, medially depressed, preceded by cervical groove, followed by 1–2 not interrupted or minutely interrupted ridges, interspersed with 2 short lateral ridges. Lateral margins clearly convex, with 7 spines: first anterolateral spine well-developed, reaching end of lateral orbital spine, second spine (hepatic) well-developed, 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, [1.1]1.5–1.6 × as long as broad, length 0.4 and breadth0.3 that of carapace; lateral margins serrated and convex, with well-developed supraocular spines, subapical spines well-developed. Pterygostomian flap ending in anterior spine, upper margin smooth or serrated.

Thoracic sternum:As wide as long or slightly wider than long, lateral margins of posterior half slightly divergent. Sternite 3 broad, [2.2]–2.5 × as wide as long, anterior margin convex. Sternite 4 widely contiguous to sternite 3; surface flattened, smooth; greatest width 2.7–[2.9] × that of sternite 3, 2.6–[2.9] × as wide as long.

Pleon: Elevated ridges upraised dorsally, with a few scattered short 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 [1.3] × broader than long, peduncle distally setose, not distinctly expanded proximally; maximum corneal diameter [0.7] × rostrum width, as wide as eyestalk.

Antennule: Article 1 slightly longer than wide, with 4 distal spines: distomesial spine well-developed; proximal lateral spine absent.

Antenna: Article 1 with prominent mesial process distally not reaching lateral antennular spine. Article 2 with small distal spines laterally and mesially. Articles 3 and 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus [0.5]–0.6 × length of ischium at midlength, with 0–1 median small spine and and 1 well-developed distal spines on extensor margin and 1 strong spine on flexor margin.

P1 (lost in holotype): 2.5–3.0 (males) × carapace length; subcylindrical, spiny and with 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 1.1 × length of carapace, 2.5–2.7 × as long as carpus. Carpus 1.8–2.4 × as long as wide. Palm 1.3–1.6 × carpus length, 2.1–2.5 × as long as broad. Fingers unarmed, 0.8 × palm length.

P2–4 (lost in most specimens): Subcylindrical, moderately setose and spinose, with few scattered plumose setae. Meri successively shorter posteriorly: P3 merus 0.8 × length of P2 merus, P4 merus [0.8]–0.9 × length of P3 merus; P2 merus, [0.6]0.8 × carapace length, [3.5]–4.7 × as long as broad, [1.0]–1.4 × as long as P2 propodus; P3 merus [4.0]–5.5 × as long as broad, [1.1]–1.3 × as long as P3 propodus; P4 merus [4.1]–5.2 × as long as broad, [0.9]–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 other than small distal spine otherwise serrated on proximal half; flexor margins of all legs irregular, with distal spine. 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 P2–4 irregular, each with distal spine. Propodi stout, [4.2–5.2]4–5 × as long as broad; extensor margin irregular, unarmed or with minute proximal spines; 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 5–6 movable spines.

Eggs. Ov. F carried approximately 5– 10 eggs of 0.3 mm diameter.

Live colour. Unknown.

Genetic data. COI and 16S, Table 1.

Distribution. French Polynesia, Philippines and Vanuatu, from 10 to 97 m.

Remarks. Phylladiorhynchus pulchrus belongs to the group of species having 5 epigastric spines, 3 spines on the anterior branchial margin, gastric region strongly convex, the rostrum leaf-like (margins clearly convex and subapical spines present), and carapace ridges upraised dorsally. The new species is closely related to P. koumac from New Caledonia and they can be distinguished by subtle differences:

- The proximal half of the extensor margin of the P2–4 propodi has well-developed spines in P. koumac , whereas these spines are obsolescent or absent in P. pulchrus .

- The P2–4 propodi are slender (6–7 × as long as wide) in P. koumac , whereas they are stout (4–5 × as long as wide) in P. pulchrus .

The sequences of P. pulchrus were 11% (COI) and 10% (16S) divergent from P. koumac . The specimens of P. pulchrus range in size from 1.4 to 2.0 mm postorbital carapace length.

Figures

FIGURE 47. Phylladiorhynchus pulchrus n. sp., A–D, F–I, holotype male 1.6 mm (MNHN-IU-2014-13849); E, paratype male 1.5 mm (MNHN-IU-2014-13868): 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 50. Rostrum, dorsal view. A, Phylladiorhynchus phlias n. sp., paratype male 1.4 mm (MNHN-IU-2014-13881). B, P. poeas n. sp., paratype male 3.3 mm (MNHN-IU-2014-13737). C, P. pollux n. sp., holotype ovigerous female 3.5 mm (MNHN-IU-2014-13797). D, P. porteri n. sp., paratype female 2.4 mm (MNHN-IU-2014-23831). E, P. priasus n. sp., paratype ovigerous female 2.1 mm (UF54422). F, P. pulchrus n. sp., paratype male 1.8 mm (MNHN-IU-2019-2675). G, P. punctatus n. sp., paratype male 1.7 mm (MNHN-IU-2019-20101). H, P. serrirostris (Melin, 1939), paralectotype male 2.3 mm (UPSTY2531). I, P. spinosus Schnabel & Ahyong, 2019, male 3.3 mm (MNHN-IU-2016-492). J, P. talaus n. sp., paratype ovigerous female 2.4 mm (WAM C43997). K, P. tiphys n. sp., holotype male 2.4 mm (MNHN-IU-2014-13794). L, P. zetes n. sp., holotype male 2.1 mm (UF30059). Scale bars: 1 mm.