Phylladiorhynchus maestratii, 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 : 85-88

Phylladiorhynchus maestratii n. sp.

( Fig. 32 )

Phylladiorhynchus ikedai . — Baba, 1991, 485 (in part, only some specimens from CALSUB Pl 16).

Type material. Holotype. Chesterfield Islands , KANADEEP Stn DW 4962, 23.0333°S, 159.4666°E, 315–1260 m, 6 September 2017: M 2.3 mm (MNHN-IU-2017-2736)

Paratypes. New Caledonia. CALSUB Pl 16, 20.6300°S, 167.0450°E, 500 m, 7 March 1989 : 1 M broken (MNHN- IU-2013-19942), 1 M 1.8 mm (MNHN-IU-2013-19943).—KANACONO Stn CP4684, 22.4000°S, 167.4000°E,

493–694 m, 14 August 2016: 1 M 1.7 mm (MNHN-IU-2017-11683).—Stn DW4749, 23.6333°S, 167.7333°E, 440– 457 m, 24 August 2016: 1 ov. F 3.1 mm (MNHN-IU-2017-11662).

Etymology. Named after Philippe Maestrati, curatorial assistant of the general mollusc collection of the Muséum national d’Histoire naturelle, Paris.

Description. Carapace: 1.1–[1.2] × as long as broad; transverse ridges with dense short setae and scattered long setae. Gastric region flattened with 4 transverse ridges: epigastric ridge indistinct, with 4 spines (2 pairs of spines laterally, sometimes with median granule); anterior protogastric ridge not medially interrupted, nearly extending laterally to carapace margin; anterior mesogastric ridge not medially interrupted, or minutely interrupted, laterally interrupted by anterior branch of cervical groove; anterior metagastric ridge scale-like. Mid-transverse ridge not interrupted, preceded by shallow cervical groove, followed by 2 uninterrupted or minutely interrupted ridges, interspersed with 1–2 short lateral ridges and occasionally with few, short scattered scales (absent in holotype). Lateral margins straight or slightly convex, with 7 spines: first anterolateral spine well-developed, reaching or slightly exceeding level of lateral orbital spine, second spine (hepatic) small, slightly dorsomesially from lateral margin, and followed by 5 branchial spines (3 anterior and 2 posterior). Rostrum dagger-like, horizontal, dorsally slightly or deeply concave, 2.0–[2.1] × as long as broad, length 0.4–[0.5] and breadth 0.3 that of carapace; lateral margins smooth, convex, with well-developed supraocular spines, subapical spines distinct. Pterygostomian flap ending in blunt tooth, upper margin smooth.

Thoracic sternum: As wide as long. Sternite 3 moderately broad 2.0–[2.3] × as wide as long anterior margin convex. Sternite 4 narrowly contiguous to sternite 3; surface depressed in midline, smooth; greatest width 3 × that of sternite 3, 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 ridges only; tergites 5–6 smooth.

Eye: Eyestalk as broad as long, peduncle distally setose, not distinctly expanded proximally, maximum corneal diameter 0.9–[1.0] × rostrum width, as wide as eyestalk.

Antennule: Article 1 1.3 × longer than wide, with 5 distal spines, distomesial spine well-developed; proximal lateral spine small.

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

Mxp3: Ischium with distinct distal spines on flexor and extensor margins. Merus half length of ischium, extensor margin with distal spine, flexor margin with 2 strong spines.

P1: [2.9] × carapace length (males), 2.8 (female), subcylindrical, spiny and with scattered long stiff setae and dense short thick setae; merus, carpus and palm with spines along mesial, dorsal and lateral surfaces, mesial spines usually stronger than others. Merus [1.1]1.1 length of carapace, [2.1]–2.3 × as long as carpus. Carpus [2.4]–2.5 × as long as wide. Palm 1.4 × carpus length, [2.9]–3.4 × as long as broad. Fingers unarmed,0.7 × palm length.

P2–4 (lost in holotype): Slender, subcylindrical, moderately setose and spinose. Meri successively shorter posteriorly: P3 merus 0.7 × length of P2 merus, P4 merus 0.9 × length of P3 merus. P2 merus, 0.8 × carapace length, 9 × as long as broad, 1.3 × as long as P2 propodus; P3 merus 5 × as long as broad, 1.3 × as long as P3 propodus; P4 merus 4 × as long as broad, 1.2 × 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 margins of P2–4 irregular; P4 lateral surface with 4 small spines. Carpi extensor margin with 8–9 small spines on extensor margin on P2–3; distal spine prominent on P2, smaller or absent in P3–4; flexor margin unarmed. Propodi moderately slender, 6.3–7.0 × as long as broad; extensor margin irregular, usually serrated, with 7–10 small spines; flexor margins with 2–3 slender movable spines in addition to distal pair. Dactyli 0.5–0.6 × length of propodi, ending in incurved, strong, sharp spine; flexor margins with 8–10 movable spines.

Eggs: no data.

Live colour. Unknown.

Genetic data. COI and 16S, Table 1.

Distribution. New Caledonia, Chesterfield Islands, from 315 to 1260 m.

Remarks. Phylladiorhynchus maestratii belongs to the group of species having the epigastric ridge with 4 spines and often one median process or scale with thick plumose setae (rarely with 5 spines), 3 spines on the anterior branchial margin of the carapace and the Mxp3 merus with two prominent spines along the flexor margin. Phylladiorhynchus maestratii is close to P. cepheus from French Polynesia and P. butes , from New Caledonia,

Chesterfield Islands, Indonesia and French Polynesia, however these species can be distinguished on basis of the following characters:

- The median epigastric process, spine or scale with thick setae is always present in P. cepheus and P. butes , whereas this process is absent or is present as a simple granule in P. maestratii .

- The rostrum is less than twice as long as wide in P. cepheus and P. butes , whereas it is more than twice as long as wide in P. maestratii .

- Thoracic sternite 4 is widely contiguous to sternite 3 in P. cepheus and P. butes , whereas it is narrowly contiguous in P. maestratii .

- The P2–4 dactyli flexor margins have 8–10 movable spines in P. maestratii , whereas these margins have 6–7 movable spines in P. cepheus and 5–8 in P. butes .

- Antennal article 2 is armed distally with well-developed mesial and lateral spines in P. butes rather than unarmed, at most with small distomesial spine or granule in P. cepheus and P. maestratii .

The genetic divergences among these species were larger than 7% (COI) and 5% (16S). The specimens of P. maestratii range from 1.6 to 3.1 mm postorbital carapace length.

Figures

FIGURE 32. Phylladiorhynchus maestratii n. sp.,A-E, holotype male 2.3 mm (MNHN-IU-2017-2736); F–J, paratype ovigerous female 3.1 mm (MNHN-IU-2017-11662): A, carapace and pleon, dorsal view. B, rostrum, dorsal view. C, thoracic sternites 3 and 4. D, right cephalic region, showing antennular and antennal peduncles, ventral view. E, left Mxp3, lateral view. F, left P1, merus and carpus, dorsal view. G, left P1, propodus and dactylus, dorsal view. H, right P2, lateral view. I, right P3, lateral view. J, right P4, lateral view. K, dactylus of right P2, lateral view. Scale bars: 1.0 mm.