Phylladiorhynchus spinosus, Schnabel & Ahyong, 2019

Schnabel, Kareen E. & Ahyong, Shane T., 2019, The squat lobster genus Phylladiorhynchus Baba, 1969 in New Zealand and eastern Australia, with description of six new species, Zootaxa 4688 (3), pp. 301-347 : 335-337

Phylladiorhynchus spinosus n. sp.

( Figs. 12 , 13 )

Galathea pusilla .— Grant & McCulloch, 1906: 49, pl. 4, figs. 5, 5a (part, Mast Head Island, Queensland).— McNeill, 1926: 305 (Capricorn Group, Queensland).

Phylladiorhynchus integrirostris .— Macpherson, 2008: 293–294. (Dampier Archipelago, Western Australia)

Phylladiorhynchus cf. integrirostris .— Hosie et al., 2015: 269.

Type material. HOLOTYPE AM P103672 (ex. NIWA 21215 ), male (3.3 mm), Phillip Island , Norfolk Island group, Australia, NZOI Stn. I78, 29.113°S, 167.938°E, 6–28 m, 22 Jul 1975 . PARATYPES NIWA 21211 , 2 males (1.0, 2.8 mm), 1 female (1.8 mm), Norfolk Island, Australia , NZOI Stn. I75 , Anson Bay , 28.75°S, 167.92°E, 70 m, 20 Jul 1975 . NIWA 21212 , 1 male (3.5 mm), 1 female (2.1 mm), Norfolk Island, Australia , NZOI Stn. P29, 28.908°S, 167.963°E, 37 m, 28 Jan 1977 . NIWA 21210 , 1 male (2.5 mm), S of Norfolk Island, Australia , NZOI Stn. P19, 29.560 S, 168.027°E, 81 m, 25 Jan 1977 . NIWA 21209 , 2 females ov. (2.8, 2.2 mm), S of Norfolk Island, Australia , NZOI Stn. P20, 29.538°S, 167.997°E, 52 m, 25 Jan 1977 . AM P72850, 1 male (1.7 mm), TAN0308/24, S of Norfolk Island, Australia, 28.907°S, 167.684°E, 111–115 m, 15 May 2003 .

Other material. Queensland, Australia: AM G5620 , 1 female ov. (3.4 mm), Mast Head Island , 23.539°S, 151.726°E, 31 m, dredged, coll. F.E. Grant. AM G.5743, 1 male (2.8 mm), 3 females ov. (2.4, 2.5, 2.8 mm), Mast Head Island , 23.539°S, 151.726°E, 4 m, coll. F.E. Grant. AM P12212, 3 females ov. (2.5, 2.6, 2.6 mm), 12 miles NE of Bustard Head, near Port Curtis , 24.017°S, 151.767°E, 15 m, from coral reef, coll. J.S. Hynd, 5 Sep 1946 .

Norfolk Ridge, Australia: NIWA 21204 , 1 male (2.6 mm), 1 female ov. (2.4 mm), NZOI Stn. D564, N of Nor- folk Island, 27.130°S, 167.983°E, 24 m, 20 Feb 1966 . NIWA 21213 , 2 males (2.2, 2.5 mm), NZOI Stn. P 28 , Norfolk Island, 28.830°S, 167.994°E, 53 m, 28 Jan 1977 . NIWA 21208 , 2 males (2.4, 2.8 mm), 4 females ov. (1.9–2.6 mm), 1 female (2.3 mm), NZOI Stn. I82 , S of Norfolk Island, 29.128°S, 168.005°E, 51 m, 22 Jul 1975 . NIWA 21205 , 1 female ov. (2.1 mm), NZOI Stn. I92 , S of Norfolk Island, 29.413°S, 168.220°E, 570–578 m, 23 Jul 1975 . NIWA 21214 , 1 male (2.0 mm), 1 female ov. (2.2 mm), NZOI Stn. I90 , S of Norfolk Island, 29.417°S, 168.093°E, 71 m, 23 Jul 1975 . NIWA 21206 , 1 male (2.8 mm), NZOI Stn. I89 , S of Norfolk Island, 29.422°S, 168.003°E, 65 m, 23 Jul 1975 .

Western Australia: AM P89996, 1 male (2.0 mm), 1 female ov. (2.0 mm), 1 female (1.6 mm), WA644, Dampier Archipelago, Legendre Island , 1 km NE of Cape Legendre, 20.355°S, 116.843°E, 27 m, small boulders, coll. P. Hutchings & L. Avery, 6 Aug 2000 . AM P90002, 1 male (2.1 mm), 1 female (2.1 mm), WA646, Dampier Archipelago , 1 km NE of Delambre Island, 20.429°S, 117.085°E, 14 m, P. Hutchings & L. Avery, 7 Aug 2000 . AM P89991, 1 female (1.1 mm), WA406, Exmouth Gulf, Bundegi Reef, near Point Murat , 21.820°S, 113.180°E, 8–9 m, dead encrusted coral, coll. R. Springthorpe, 4 Jan 1984 . AM P89988, 1 male (2.1 mm), 1 female (1.3 mm), WA404, Exmouth Gulf, Bundegi Reef, near Point Murat , 21.820°S, 113.180°E, 8–9 m, pink sponge on dead coral, coll. J. Lowry, 4 Jan 1984 . AM P89975, 2 males (1.7, 2.4 mm), WA526, Goss Passage, Beacon Island , foot of reef slope, 28.425°S, 113.780°E, 33 m, dead coral embedded in fine sediment, coll. P. Hutchings, 23 May 1994 . AM P89978, 1 male (1.9 mm), 1 female (2.2 mm), WA526, Goss Passage, Beacon Island , foot of reef slope, 28.425°S, 113.780°E, 33 m, dead coral embedded in fine sediment, coll. P. Hutchings, 23 May 1994 . AM P89985, 1 male (2.0 mm), FRV Flinders Stn 29, WA542, Houtman Abrolhos Islands, Wallabi Group , 28.543°S, 113.776°E, 45 m, white bleached rhodoliths, coll. P. Hutchings, 28 May 1994 .

Diagnosis. Rostrum lateral margins nearly straight; subapical spines present. Carapace with 2 epigastric spines; metagastric ridge between third branchial marginal spines medially continuous; anterior branchial margin with 3 spines; hepatic spine present. Thoracic sternite 3 anterior margin biconcave, with obtuse median projection. Antennular article 1 with 5 spines: distomesial spine large, reaching end of lower distolateral spine, overreached by upper distolateral and first lateral spines; second (proximal) lateral spine long, slender. Antennal article 1 mesial process distally falling well short of second lateral antennular spine; article 2 distolateral spine distinctly larger than distomesial spine; article 3 with small to minute distomesial spine, distolaterally unarmed. Maxilliped 3 merus with 1 prominent spine on flexor margin. P2–4 dactylus extensor margin with sharp upright spines at bases of movable spines.

De s cription. Carapace: Length 0.8–[0.9] × width; transverse ridges with dense short setae, and few scattered longer setae. Gastric region with 4 interrupted anterior transverse ridges: epigastric ridge distinct, with 2 spines; anterior protogastric ridge continuous, nearly extending laterally to carapace margin; anterior mesogastric ridge continuous, broken laterally by cervical groove, laterally continuing uninterrupted to first branchial spine; metagastric ridge continuous, broken by cervical groove, laterally continuing to third branchial spine; short striae sometimes scattered between ridges, central posterior metagastric ridge always a distinct curved stria. Mid-transverse ridge uninterrupted, preceded by shallow cervical groove, followed by 2 complete, uninterrupted ridges, interspersed with 3 short lateral ridges and few short, scattered striae. Lateral margins distinctly convex, with 8 spines; 2 spines in front of (anterolateral, hepatic) and 6 spines behind (3 anterior branchial, 3 posterior branchial) distinct anterior cervical groove.Anterolateral spine well-developed, nearly reaching lateral orbital spine, subequal in size. Hepatic spine distinct, set slightly mesially from lateral margin. Anterior branchial spines subequal in size. Posterior branchial spines with first spine subequal to anterior branchial spines, progressively smaller posteriorly. Rostrum length [0.4]–0.7 × pcl, relatively slender, length-width ratio about 2.0, distance between basal pair of rostral spines about 0.3 × carapace width; dorsal surface concave; lateral margins slightly convex, sub-apical spines distinct. Pterygostomian flap anteriorly with sharp anterior spine; surface unarmed, with series of short striae.

Thoracic sternum: Sternal plastron as wide as or slightly wider than long, length-width ratio 0.8–1.0 [0.9], lateral margins slightly divergent posteriorly. Sternite 3 width 1.5–[1.7] × length; anterior margin biconcave, median process obtusely triangular; lateral margins rounded.

Abdomen: Tergites 2–4 with anterior and posterior transverse ridges; tergites 5–6 smooth, without elevated ridges.

Eye: Eye length [1.4]–1.5 × width, peduncle distally setose, not distinctly expanded proximally, with few short transverse striae on lateral surface; cornea not dilated.

Antennule: Article 1 with 5 well-developed distal spines: distomesial spine large, reaching end of lower disto- lateral spine; paired distolateral spines present; proximal lateral spine long and slender. Short striae covering mesial surfaces.

Antenna: Article 1 with prominent mesial process, distally falling well short of lateral spine of antennule. Article 2 with distinct distal spines laterally and small spine mesially. Article 3 with small to minute mesial spine, laterally unarmed. Article 4 unarmed.

Maxilliped 3 (Mxp3): Ischium with distinct distal spines on both flexor and extensor margins; crista dentata with regular row of spines along entire margin. Merus about as long as ischium at midline, with prominent distal spine on extensor margin, subequal to prominent spine at midlength of flexor margin; otherwise unarmed.

Cheliped: Length 2.4–4.0 [3.8] × pcl (2.4–2.7 in females, 3.0–4.0 in males); subcylindrical, spiny and setose. Ischiomerus [1.0–1.6] × pcl, [2.0]–3.0 × carpus length; with rows of spines, mesial spines strongest. Carpus with rows of spines on all surfaces, 1 or 2 mesial spines most prominent. Propodus palm 1.0–1.5 [1.1] × carpus length, length-width ratio 1.7–2.1 [1.9], with 4 parallel rows of spines (2 mesial, 1 at about dorsal midline, 1 close to lateral margin). Fingers [0.8]–1.3 × palm length; surface with short setiferous striae, unarmed, distally excavated, may be distinctly gaping. Pollex outer margin unarmed, occlusal margin with 1 prominent process. Dactylus with 1 small to distinct outer proximal spine, occlusal margin with prominent basal processes; distally with row of spines along curved margin; tip excavated.

Walking legs (P2–4): relatively stout, subcylindrical, moderately setose and spinose. Merus successively shorter posteriorly (P2 merus 1.1–[1.2] × P3 merus length, P3 merus [1.2]–1.3 × P4 merus length). P2 merus length 0.6– [0.7] × pcl, 1.1–[1.2] × P2 propodus length, length [4]–5 × width. P3 merus length [1.0]–1.1 × P3 propodus length; length [3]–4 × width. P4 merus length 0.8–[0.9] × P4 propodus length; length [3]–4 × width. Extensor margin of P2 and P3 with regular row of spines, proximally diminishing, with prominent distal spine; P4 extensor margin irregular but unarmed, distal spine absent; flexor margins of all legs irregular, with rows of projecting scales and prominent distal spine; P4 lateral surface with median row of 2 or 3 small spines, absent on P2 and P3. Carpus with 3 or 4 spines on extensor margin on P2–3, unarmed on P4; distal spine prominent on P2–3, minute on P4; row of small spines below extensor margin on lateral surface of P2–3, unarmed on P4; flexor margin unarmed. P2–4 propodus length 4–5 × height; extensor margin irregular, unarmed on all legs; flexor margin with 6–8 slender movable spines in addition to distal pair. Dactylus length 0.5–0.7 [0.6] × propodus length, ending in incurved, strong, sharp spine; flexor margin lined with fixed upright spines and 6–8 movable spines articulating at base of fixed spines.

Size. Male pcl 1.0– 3.5 mm, female pcl 1.8–2.8 mm, ovigerous female pcl ≥ 1.9 mm.

Colour in life. Not known.

Genetic data. Not available.

Etymology. Spinosus is the Latin adjective for prickly, thorny or spiny, used to indicate the unusual dactylar spines at the base of each movable spine.

Distribution. So far only known from Queensland, Norfolk Island, the Norfolk Ridge, and Western Australia; 4–81 m except for one record at 570– 578 m.

Remarks. Phylladiorhynchus spinosus n. sp. belongs to the ‘ integrirostris’ group, with a single pair of epigastric spines, which it also shares with P. triginta n. sp. Distinguishing characters between P. integrirostris , P. spinosus n. sp. and P. triginta n. sp. are discussed under the former species above.

This new species is the only known species of Phylladiorhynchus from the study area that has the walking leg dactyli with distinct, fixed, upright, flexor spines at the base of each movable corneous spine (present also in P. nudus from northwestern Australia). This character is common in the closely related genus Galathea (see Macpherson & Robainas-Barcia 2015) but unusual in Phylladiorhynchus .

The known distribution of P. spinosus is disjunct, with locations from the Tasman Sea, northern Queensland and Western Australia (Abrolhos Islands and Dampier Archipelago). It is possible that more than one species is currently included in P. spinosus , but the Tasman Sea and Queensland specimens agree well in all respects. The Western Australian specimens examined here, however, differ subtly in the size of the distal spines on antennal article 2, being subequal rather than distinctly unequal. Unfortunately, however, the specimens are incomplete, all lacking chelipeds. Although possibly representing a different species, the Western Australian form (including Macpherson’s (2008) records from the Dampier Archipelago) are herein referred to P. spinosus pending further study.

Specimens of P. spinosus were collected from 81 m or shallower, except for one specimen recorded at 570–578 m (NIWA 21205; NZOI stn I92). The specimen agrees in all respects with the shallow water specimens including the distinct pereopod 2–4 dactylar spines; we suspect that this station record is erroneous.

Figures

FIGURE 12. Distribution records for Phylladiorhynchus pusillus (white circles), P. spinosus n. sp. (crossed circles) and P. triginta n. sp. (black circles). Lines demarcating the EEZ for both Australia and NZ shown.

FIGURE 13. Phylladiorhynchus spinosus n. sp., holotype male, 3.3 mm (AM P103672): A, carapace and abdomen, dorsal view. B, sternal plastron. C, left cephalic region, showing antennular, antennal peduncles and anterior portion of pterygostomian flap, ventral view. D, left Mxp3, lateral view. E, left cheliped, dorsal view. F, left cheliped, ischium, mesial view. G–I, right P2–4, lateral view. J, right P3, distal portion of propodus and dactylus. Scale bars: 2 mm.