Phylladiorhynchus idas, 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 : 48-49

Phylladiorhynchus idas n. sp.

( Fig. 17 )

Type material. Holotype. French Polynesia. TARASOC Stn DW 3393, 15.8200°S, 148.2800°W, 800 m, 7 October 2009: F 2.5 mm (MNHN-IU-2014-13842).

Etymology. From the name Idas, an Argonaut, son of Aphareus and Arene. The name is considered a substantive in apposition.

Description. Carapace: Slightly longer than broad; transverse ridges with short setae. Gastric region flattened, with 4 transverse ridges: epigastric ridge indistinct, with 3 spines (1 median and 2 lateral spines) and some outer granules; anterior protogastric ridge medially interrupted, nearly extending laterally to carapace margin; anterior mesogastric ridge medially interrupted, laterally interrupted by anterior branch of cervical groove; anterior metagastric ridge indistinct, with few small scales in the anterior metagastric area. Mid-transverse ridge not interrupted, slightly medially depressed, preceded by shallow or indistinct cervical groove, followed by 2 uninterrupted or minutely interrupted ridges, interspersed with 1 short lateral ridge. Lateral margins slightly convex, with 6 spines: first anterolateral spine well-developed, reaching end of lateral orbital spine, second spine (hepatic) minute but distinct, slightly dorsomesially from lateral margin, and followed by 4 branchial spines (2 anterior spines, first well-developed, followed by a second obsolescent to undistinct spine, and 2 posterior spines). Rostrum triangular, horizontal, dorsally flattish or slightly concave, [1.1] × as long as broad, length [0.3] and breadth [0.3] that of carapace; lateral margins smooth and slightly concave proximally, with well-developed supraocular spines, subapical spines absent. Pterygostomian flap ending in round, upper margin smooth.

Thoracic sternum: As wide as long. Sternite 3 broad, [3.0] × as wide as long, anterior margin convex, with a median feeble excavation, moderately produced anterolaterally. Sternite 4 widely contiguous to sternite 3; surface not depressed in midline, smooth; greatest width [2.5] × that of sternite 3, [2.8] × as wide as long.

Pleon: Elevated ridges with short setae and with few scattered long 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 as broad as long, peduncle distally setose, not distinctly expanded proximally; maximum corneal diameter [1.4] × rostrum width, as wide as eyestalk.

Antennule:Article 1 more than 1.5 × longer than wide, with 5 spines: distomesial spine well-developed; proximal lateral spine small.

Antenna: Article 1 with prominent mesial process, nearly reaching lateralmost antennular spine end. 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 [0.7] × length of ischium at middle length, with well-developed distal spine on extensor margin and 2 strong spines on flexor margin (median spine distinctly curved).

P1: [3.8] × carapace length; subcylindrical, spiny and with several plumose setae on merus, and carpus and long stiff setae on palm and fingers; merus, carpus and palm with spines along mesial, dorsal and lateral surfaces, distal and mesial spines usually stronger than others. Merus [1.5] length of carapace, [2.4] × as long as carpus. Carpus [3.2] × as long as wide. Palm [1.2] × carpus length, [3.2] × as long as broad. Fingers subequal in length to palm; fixed finger unarmed; movable finger with well-developed basal spine.

P2–4: Slender, subcylindrical, moderately setose and spinose. Meri successively shorter posteriorly: P3 merus [0.6] × length of P2 merus, P4 merus [0.9] × length of P3 merus. P2 merus, as long as carapace length, [9.2] × as long as broad, [1.4] × as long as P2 propodus; P3 merus [8.3] × as long as broad, [1.2] × as long as P3 propodus; P4 merus [7] × as long as broad, [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, with distal spine; flexor margins of P2–4 irregular, each with distal spine; P4 lateral surface with median row of 4 small spines, absent in others. Carpi armed on extensor margin with 1 spine on P2, unarmed on P3–4, distal spine prominent on P2–4. Propodi sharply slender, [10.0–10.1] × as long as broad; extensor margin irregular, usually unarmed; flexor margin with 2–4 slender movable spines in addition to distal pair. Dactyli [0.5] × length of propodus, ending in incurved, strong, sharp spine; flexor margin with 5–6 movable spines.

Eggs. No data.

Live colour. Unknown.

Genetic data. No data.

Distribution. French Polynesia, 800 m.

Remarks. Phylladiorhynchus idas resembles P. kermadecensis Schnabel & Ahyong, 2019 , from New Zealand and P. punctatus from New Caledonia. However, the species can be distinguished by the following characters:

- The carapace has 5 epigastric spines in P. kermadecensis and P. punctatus , whereas there are 3 spines and a few granules in P. idas .

- The anterior protogastric ridge is not medially interrupted or with a small median gap in P. kermadecensis and P. punctatus , whereas the anterior protogastric ridge is medially interrupted in P. idas .

- The anterior metagastric ridge is medially interrupted in P. kermadecensis whereas this ridge is scale-like in P. idas .

- Posterior branchial margin with one spine in P. kermadecensis , whereas there are 2 spines in P. idas and P. punctatus .

- The extensor margin of the P2–3 propodus is usually armed with 2 proximal spines in P. kermadecensis and P. punctatus , whereas these margins are usually unarmed in P. idas .

- The flexor margin of the P2–4 dactyli have 10–11 movable spines in P. kermadecensis , whereas there are 5–6 movable spines in P. idas and 6–7 in P. punctatus .

Figures

FIGURE 17. Phylladiorhynchus idas n. sp., holotype ovigerous female 2.5 mm (MNHN-IU-2014-13842): 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.