Phylladiorhynchus phlias, 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 : 110-111

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Phylladiorhynchus phlias

n. sp.

Phylladiorhynchus phlias n. sp.

( Figs. 42 View FIGURE 42 , 50A View FIGURE 50 , 55I View FIGURE 55 )

Type material. Holotype. Papua New Guinea. KAVIENG Stn KZ 16, 02.5783°S, 150.7916°E, 1–2 m, 23 June 2014: ov. F 2.2 mm (MNHN-IU-2014-13535). GoogleMaps

Paratypes. Papua New Guinea. PAPUA NIUGINI Stn PS 09, 05.2050°S, 145.8133°E, 8–10 m, 9 November 2012: 1 M 1.2 mm, 1 ov. F 1.8 mm (MNHN-IU-2014-13886).— Stn PD 19, 05.0900°S, 145.8083°E, 10 m, 13 November 2012: 3 M 1.2–1.8 mm, 2 ov. F 1.5–1.7 mm, 2 F broken (MNHN-IU-2019-2674), 1 ov. F 1.3 mm (MNHN-IU-2013-703).— Stn PS 13, 05.0984°S, 145.8210°E, 8 m, 30 December 2012: 7 M 1.1–1.4 mm, 3 ov. F 1.4–1.6 mm, 1 F 1.0 mm (MNHN-IU-2014-13881) GoogleMaps .

Other material. Papua New Guinea. PAPUA NIUGINI Stn PD 24, 05.0883°S, 145.8100°E, 3–6 m, 14 November 2012: 2 ov. F 1.5–1.9 mm 2 F 1.9–2.0 mm (MNHN-IU-2019-2660), 1 M 1.4 mm (MNHN-IU-2016-452).— Stn PD 65, 05.1416°S, 145.8083°E, 1–4 m, 1 December 2012: 1 M 1.3 mm (MNHN-IU-2014-139139).— Stn PB 50, 05.0783°S, 145. 05°04.7’S, 145°48.9’E 8150°E, 3 m, 30 December 2012: 1 M 1.7 mm (MNHN-IU-2016-1492).— Stn PS 12, 05.0888°S, 145.8094°E, 6 m, 30 December 2012: 1 M 1.4 mm, 2 ov. F 1.3–1.5 mm, 2 F 1.1–1.4 mm (MNHN-IU-2014-13866).— Stn PS 18, 05.0266°S, 145.8009°E, 16 m, 30 December 2012: 1 ov. F 1.5 mm (MNHN- IU-2019-2666).—KAVIENG Stn KS 07, 02.6866°S, 150.6866°E, 8 m, 4 June 2014: 1 F 1.4 mm (MNHN-IU-2016- 5832).— Stn KD 36, 02.5850°S, 150.4833°E, 8 m, 16 June 2014: 1 F 1.4 mm (MNHN-IU-2014-13695) GoogleMaps .

Etymology. From the name Phlias, an Argonaut, son of Dionysus and Ariadne. The name is considered a substantive in apposition.

Description. Carapace: Robust or massive, sexually dimorphic (wider on females) 0.9–1.0 (males), [0.7]–0.8 (females) × as long as broad; transverse ridges elevated, upraised dorsally, with very few short setae. Gastric region convex (upraised) with some transverse ridges: epigastric ridge indistinct, unarmed, with some scales, anterior protogastric ridge not medially interrupted, laterally interrupted with some scales to carapace margin, sometimes followed by a few some short scales posteriorly; anterior mesogastric ridge scale-like, otherwise indistinct, laterally interrupted by anterior branch of cervical groove, laterally continuing with few scales; often followed by short scales; anterior metagastric ridge scale-like, followed by few scales on posterior metagastric region. Mid- transverse ridge not interrupted, preceded by shallow or indistinct cervical groove, followed by 2 uninterrupted or minutely interrupted ridges, interspersed with 1 laterally interrupted, complete or scale-like ridge and 1 short lateral ridge. Lateral margins clearly convex, with 4–5 spines: first anterolateral spine well-developed, reaching end of lateral orbital spine, hepatic spine absent, followed by 3–4 spines (2 anterior well-developed branchial spines subequal in size, second slightly dorsomesially from lateral margin, 1–2 posterior branchial spines very small). Rostrum bottle-shaped (proximally straight and distally convex), horizontal, dorsally flattish or slightly concave, [1.1]–1.3 (females), 1.8 (males) × as long as broad, length [0.3]–0.5 and breadth 0.2 that of carapace; lateral margins finely serrated, with well-developed supraocular spines, subapical spines small. Pterygostomian flap ending in blunt tooth; upper margin smooth.

Thoracic sternum:As wide as long or slightly wider than long, lateral margins of posterior half slightly divergent. Sternite 3 moderately broad, [2.6]1.7–2.7 × as wide as long, anterior margin straight or slightly convex. Sternite 4 widely contiguous to and wider than sternite 3; surface flattened, smooth; greatest width 3.3–[3.4] × that of sternite 3, 2.4–[2.5] × as wide as long.

Pleon: Elevated ridges upraised dorsally, with few short setae.Tergites 2–3 with anterior and posterior transverse elevated ridges; tergite 4 with anterior transverse ridge only; tergites 5–6 smooth.

Eye: Eyestalk length about 0.9 × broader than long, peduncle distally setose, not distinctly expanded proximally; maximum corneal diameter 0.9 × rostrum width, as wide as eyestalk.

Antennule: Article 1 slightly longer than wide, with 3–4 distal spines: distomesial spine minute or absent; proximal lateral spine absent.

Antenna: Article 1 with prominent mesial process distally not reaching lateral antennular spine. Article 2 unarmed, sometimes with minute distomesial spine. Articles 3 and 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus [0.4]0.4 × length of ischium, with 0–1 median small spine and well-developed distal spine on extensor margin and 2 smaller spines, subequal in size, on flexor margin.

P1 (lost in holotype): 2.2–2.3 × carapace length (males), 1.4 (females); subcylindrical, with scattered spines and long stiff setae, with some thick short setae; merus, carpus and palm with spines along mesial, dorsal and lateral surfaces, distal and mesial spines usually stronger than others. Merus 0.5–0.8 length of carapace, 1.7–2.0 × as long as carpus. Carpus 1.3–1.7 × as long as wide. Palm 0.8–1.0 × carpus length, 1.2–1.3 × as long as broad irregular and unarmed in all the surfaces, otherwise a small spine on basal mesial margin. Fingers unarmed, 1.0–1.3 × palm length.

P2–4 (lost in most specimens): Stout, moderately setose and spinose. Meri successively shorter posteriorly: P3 merus 0.9 × length of P2 merus, P4 merus 0.7–0.9 × length of P3 merus. P2 merus, 0.4–0.5 × carapace length, 3.2 × as long as broad, 1.2–1.3 × as long as P2 propodus; P3 merus 3.2–3.5 × as long as broad, 1.0–1.2 × as long as P3 propodus; P4 merus 2.8–3.2 × as long as broad, as long as P4 propodus; extensor margins of P2–3 irregular, unarmed, with small distal spine; P4 extensor margin irregular, unarmed, distal spine absent; flexor margins of all legs irregular, with distal spine on P2–3, distal spine absent in P4. Carpi extensor margins irregular or granulated, unarmed on P2–4. Propodi stout, 3.5–4.5 × as long as broad; extensor margins irregular, usually unarmed; flexor margins with 2–4 slender movable spines in addition to distal pair. Dactyli 0.7–0.9 × length of propodi, ending in incurved, strong, sharp spine; flexor margin with 4–6 well-developed dactylar spines, each with movable spinule.

Eggs: Ov. F carried approximately 5– 15 eggs of 0.4–0.5 mm diameter.

Live colour. Body whitish- pale yellow, with small brownish spots. P1 whitish-pale yellow. P2–4 whitish, with translucid bands.

Genetic data. COI and 16S, Table 1.

Distribution. Papua New Guinea, between 1 and 16 m.

Remarks. Phylladiorhynchus phlias belongs to the group of species characterized by having the epigastric ridge unarmed, the carapace and pleon ridges elevated, upraised, and dactylar spines on the flexor margins of the P2-4 dactyli. The closest species are P. phanus , from Papua New Guinea, and P. marina , from Vanuatu, however these species can be distinguished on the basis of the following morphological characters:

- The rostrum is bottle-shaped in P. phlias , whereas it is leaf-like in the other species.

- The hepatic spine is absent in P. phlias , whereas it is present in P. phanus and P. marina .

- The anterior branchial margin has 2 branchial spines in P. phlias , whereas this margin has 3 spines in in the other species.

The genetic divergences between P. phlias , and these species exceeded 15% (COI) and 12% (16S), respectively. The two sequences of P. phlias from Papua New Guinea diverged 0.5% for COI. The specimens of P. phlias range in size 1.1–2.2 mm postorbital carapace length.