Phylladiorhynchus heptacanthus, 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 : 44-45

Phylladiorhynchus heptacanthus n. sp.

( Figs. 15 , 21C )

Type material. Holotype. Chesterfield Islands . KANADEEP Stn DW 4960, 23.0667°S, 159.4667°E, 310 m, 6 September 2017: F 2.1 mm (MNHN-IU-2017-2534).

Paratypes. Chesterfield Islands . EBISCO no Stn details: 1 ov. F 1.8 mm (MNHN-IU-2014-13851). KANADEEP Stn DW 4950, 24.0833°S, 159.7000°E, 330–500 m, 5 September 2017: 1 M 2.2 mm (MNHN-IU-2017-2515).— Stn CP 4953, 24.1667°S, 159.6833°E, 270–320 m, 5 September 2017: 4 M 1.0– 1.4 mm, 2 ov. F 1.6–1.8 mm, 6 F 1.4–1.8 mm (MNHN-IU-2017-3326) .

Other material. Chesterfield Islands . KANADEEP Stn DW 4961, 23.0333°S, 159.4666°E, 300–430 m, 6 September 2017: 1 F 2.2 mm (MNHN-IU-2017-2729) .

New Caledonia. KANACONO Stn CP 4673, 22.7833°S, 167.4500°E, 244–285 m, 13 August 2016: 1 ov. F 1.9 mm (MNHN-IU-2017-11724) .

Etymology. From the Greek hepta, seven, and akantha, spine, in reference to the seven spines on the dorsal surface of the carapace.

Description. Carapace: Robust or massive, [0.8]–0.9 × 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 transverse scale-like ridges: epigastric ridge indistinct, with 5 spines (1 median and and 2 pairs of spines laterally), followed by 1 scale behind median epigastric spine; anterior protogastric ridge undistinct or scale like, not continuing laterally to carapace margin, armed with 1 parahepatic spine on each side, behind lateralmost epigastric spines, posterior protogastric area scale-like; anterior mesogastric ridge indistinct with some scales or scale-like, laterally continuing with few scales, posterior mesogastric ridge scale-like; anterior metagastric ridge scale-like, followed by small scale(s) on posterior metagastric region. Mid-transverse ridge not interrupted, medially depressed, serrated laterally, preceded by distinct cervical groove, followed by 2uninterrupted or minutely interrupted ridges, interspersed with 1 short lateral ridge and some scales. Lateral margins clearly convex, with 7 spines: first anterolateral spine well-developed, not reaching anteriorly end of strong lateral orbital spine, second spine (hepatic) well-developed, and followed by 5 branchial spines (3 anterior and 2 posterior). Rostrum leaf-like to subtriangular, dorsally sharply concave in anteroposterior midline, [1.1]1.0–3.0 × as long as broad, length [0.4]–0.4 and breadth [0.3]0.3 that of carapace; lateral margins serrated and convex, with small supraocular basal spines, subapical spines absent. Pterygostomian flap ending in anterior spine, upper margin smooth, with series of uprised ridges.

Thoracic sternum: 0.9 × as long as wide. Sternite 3 moderately broad, [2.4]–2.6 × as wide as long, anterior margin straight, or slightly convex. Sternite 4 widely contiguous to sternite 3; surface depressed in midline, smooth; greatest width 2.6–[2.7] × that of sternite 3, 2.5 × 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 [1.5]1.3–1.6 × broader than long, peduncle distally setose, not distinctly expanded proximally; maximum corneal diameter [0.5]–0.6 × rostrum width, narrower than eyestalk.

Antennule: Article 1 1.4 longer than wide, with 5 spines, distomesial spine well-developed, proximal lateral spine small.

Antenna: Article 1 with prominent mesial process, distally falling well short of lateralmost antennular spine. Article 2 with small distal spines laterally and mesially. Article 3 with minute or distinct distomesial and distolateral spines. Article 4 unarmed.

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus [0.5] × length of ischium at midlength, with 0–[1] distal spine on extensor margin and 2 spines on flexor margin.

P1: [2.2] (female) (lost in most specimens) × carapace length; subcylindrical, spiny and with scattered long stiff setae and scattered plumose setae; merus, carpus and palm with spines along mesial, dorsal and lateral surfaces, distal and mesial spines usually stronger than others. Merus as long as carapace. Carpus [1.9]–2.0 × as long as wide. Palm 1.2–[1.3] × carpus length, [2.3] × as long as broad. Fingers unarmed, [0.7]–0.8 × palm length.

P2–4: (lost in most specimens) Stout, subcylindrical, moderately setose and spinose. Meri successively shorter posteriorly: P3 merus [0.8] × length of P2 merus, P4 merus [0.8] × length of P3 merus. P2 merus, 0.6 × carapace length, 4.4 × as long as broad, [0.9] × as long as P2 propodus; P3 merus [5] × as long as broad, [1.2] × as long as P3 propodus; P4 merus [4.6] × as long as broad, [0.9] × as long as P4 propodus; extensor margin of P2–P3 with row of spines, proximally diminishing, with prominent distal spine; P4 extensor margin with 2 spines, distal spine absent; flexor margins of P2–4 irregular,with distal spine; P2–4 lateral surface with short striae. Carpi with 1–2 spines on extensor margin on P2–3, gap between the marginal and the distal spine, serrated on P4; distal spine prominent on P2–4; P2–4 flexor margins irregular, with distal spine. Propodi moderately slender, [6.8]–7.0 × as long as broad, extensor margin irregular, flexor margin with 2–3 slender movable spines in addition to distal pair. Dactyli 0.6–0.7 × length of propodi, ending in incurved, strong, sharp spine; flexor margin with 5–6 movable spines.

Eggs. Ov. F carried approximately 5– 15 eggs of 0.5–0.6 mm diameter.

Colour. After some months in ethanol: light orange with reddish spots and patches remaining in carapace, rostrum and pleon.

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

Distribution. New Caledonia and Chesterfield Islands, depth 244– 500 m.

Remarks. Phylladiorhynchus heptacanthus belongs to the group of species having 5 epigastric spines, 3 spines on the anterior branchial margin and a leaf-like rostrum. The closest species is P. eneus , from Indonesia, Philippines, Papua New Guinea and New Caledonia. However, P. heptacanthus is easily distinguished from this species by the presence of parahepatic spines, being absent in P. eneus . Furthermore, the rostrum supraocular basal spines are small in P. heptacanthu s, whereas they are well-developed in P. eneus .

The specimens of P. heptacanthus range from 1.0 to 2.2 mm postorbital carapace length. The COI divergence (mini-barcode fragment) between P. eneus and P. heptacanthus was 22%.

Figures

FIGURE 15. Phylladiorhynchus heptacanthus n. sp., holotype female 2.1 mm (MNHN-IU-2017-2534):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, left P3, lateral view. H, right P4, lateral view. I, dactylus of left P2, lateral view. Scale bar: A, E-H = 1.0 mm; B–D, I = 0.6 mm.

FIGURE 21. Rostrum, dorsal view. A, Phylladiorhynchus euryalus n. sp., paratype male 1.8 mm (UF34732). B, P. gustavi n. sp., paratype male 1.7 mm (UF9756). C, P. heptacanthus n. sp., holotype female 2.1 mm (MNHN-IU-2017-2534). D, P. hylas n. sp., paratype female 1.6 mm (MNHN-IU-2016-495). E, P. integrirostris (Dana, 1852), male 1.6 mm (UF15285). F, P. integrus (Benedict, 1902), ovigerous female 3.2 mm (MNHN-IU-2014-13853). G, P. iphiclus n. sp., holotype ovigerous female 2.3 mm (MNHN-IU-2019-2662). H, P. janiqueae n. sp., paratype male 1.8 mm (MNHN-IU-2016-482). I, P. jeffkinchi n. sp., paratype male 2.7 mm (MNHN-IU-2014-13565). J, P. joannotae n. sp., paratype male 2.1 mm (MNHN-IU-2014-20055). K, P. joannotae n. sp., holotype ovigerous female 2.1 mm (MNHN-IU-2014-13805). L, P. koumac n. sp., paratype male 1.5 mm (MNHN-IU- 2014-20121). Scale bars: 1 mm.