Indopinnixa arabica Jr, Anker & Naruse, 2024, n. sp.
Creators: name: Lasley Jr, Robert M.
name: Anker, Arthur
name: Naruse, Tohru
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Pinnotheridae
Indopinnixa
Indopinnixa arabica

description: Indopinnixa arabica n. sp.
(Figs. 1–4)
Type material. Holotype: FLMNH UF 65451, male (6.7/3.2), BOMAN-12367, Oman, Sur, stn OM22-92, 22.56821°N, 59.54071°E, coastal bay near Lighthouse, intertidal sandflat in large bay, depth 0–1 m, suction pump, coll. G. Paulay et al., 12.02.2022. Paratypes: FLMNH UF 63423, 1 male (4.1/2.3), 1 female (3.7/2.0), BOMAN-10891, Oman, west of Muscat, Al-Sawadi Beach, stn OM22-73 A, 23.78195°N, 57.79168°E, large intertidal sandflat, depth 0–1 m, suction pump, coll. A. Anker et al., 02.02.2022; FLMNH UF 63411, 1 male (4.0/2.2), BOMAN-10869, same collection data as for previous specimens; FLMNH UF 63802, 1 male (5.5/3.1), BOMAN-10871, same collection data as for previous specimens; FLMNH UF 63804, 1 male (5.5/3.2), BOMAN-10889, same collection data as for previous specimens; FLMNH UF 63803, 1 ovig. female (5.3/2.7), BOMAN-10870, same collection data as for previous specimens.
Description. Males. Carapace (Fig. 1A) transversely ovate, 2.1 times wider than long, dorsally slightly convex, punctate, pilose, with dense row of plumose setae near anterolateral and lateral margins; anterolateral margin arcuate, demarcated with line of granules obscured by setae; dorsal regions poorly defined; hepatic region swollen, mesially demarcated by low, sinuous groove; urogastric fossa forming wide depression; oblique groove parallel to posterolateral margin widening laterally to form low concavity between antero- and posterolateral margins. Front (Fig. 1B) bilobed, wider than orbit, projecting beyond orbits, with medial tuft of setae. Supraorbital margin entire, confluent with infraorbital margin. Infraorbital margin smooth, entire. Subhepatic region with ovate, glabrous region bound by setose sulcus bordering suborbital and subhepatic regions, suborbital crista, and lateral oblique sulcus; suborbital region narrow; pterygostomial region smooth with oblique concavity.
Eyes (Fig. 1A, B) small, completely filling orbit; ocular peduncle stout; cornea narrower than peduncle, darkly pigmented. Antennules folding obliquely with subglobular basal articles. Antennal article 1 positioned low on epistome, mesioventral margin intruding into margin of buccal cavity; articles 2 and 3 fused, subquadrate, broader than long, just entering orbital hiatus. Epistome longitudinally narrow, posterior margin medially obtusely triangular, lateral margins concave.
Mxp3 (Figs. 1B, 2C) elongate, almost completely covering buccal cavity.Ischium and merus fused, subtriangular, lacking median sulcus, outer margin lined with short, plumose setae. Carpus shorter than ischiomerus measured along medial axis, outer margin lined with short plumose setae. Propodus subovate, spatuliform, tapering and rounded distally. Dactylus subovate, spatuliform, originating from about mid-section of ventral margin of propodus. Mesial margins of propodus and dactylus with comb of very long setae. Exopod completely hidden by outer margin of ischiomerus in situ, shorter than ischiomerus; flagellum shorter than ischiomerus.
Chelipeds (Fig. 1D, E) subequal, with smooth surfaces. Basis and ischium smooth, fused, with visible suture. Merus short, glabrous on inner and lower surfaces; inner surface concave, with 3 granules proximally on outer margin; flexor margin and extensor surface covered with long plumose setae. Carpus with dorsal and external surfaces largely pilose and with some long plumose setae. Chela short, stout. Manus with longitudinal row of plumose setae on middle of outer surface; dorsal margin to dorsal half of outer surface densely pilose and with scattered long setae, except for glabrous patch near junction with dactylus; ventral half of outer surface glabrous, except for additional longitudinal row of plumose setae extending from immovable finger. Fingers stout, forming narrow hiatus when closed; hiatus filled with plumose setae, obscuring cutting margins; fingertips pointed, crossing when fingers closed; dactylus nearly straight, cutting margin subdistally armed with row of basally fused teeth.
Ambulatory legs (P2–5; Fig. 1A) moderately long, P4> P3> P2> P5. P2 and P3 similar in proportions, moderately slender; basis and ischium fused, with visible suture; merus elongate, smooth, with extensor and flexor margins covered with plumose setae; upper margin of junction with carpus lined with short setae; carpus and propodus smooth, with upper surfaces covered with short plumose setae; dactylus elongate, nearly straight. P4 largest and broadest; basis and ischium fused, with visible suture; merus enlarged, subovate in dorsal view; extensor margin lined with granules and long, plumose setae; upper surface with parallel row of granules and setae, dissipating half-way to carpus; upper margin with sparse, short setae; flexor margin with sinuous row of granules; flexor surface covered with plumose setae; carpus smooth, except for row of granules on extensor margin; extensor surface largely covered with pilosity and bearing short plumose setae; propodus stout, longer than carpus; extensor surface covered with pilosity and bearing short plumose setae; flexor surface covered with short and long plumose setae bordered on either side by longitudinal, parallel rows of prominent granules; dactylus stout. P5 short, stout; flexor and extensor margins lined with long, plumose setae.
Thoracic sternum (Fig. 1C) wide; sternites 1 and 2 fused, recessed into buccal cavity with median part of sternite 3, obscured by setae; only lateral parts of sternite 3 clearly visible; sternite suture 3/4 distinct; sternite 8 wide, not covered by pleon, partially visible in dorsal view. Sterno-pleonal cavity deep, connected with buccal cavity; margins along sternites 4–6 granular; postero-mesial margin of sternite 6 produced, forming coaptation with pleon; pressbutton pleonal locking mechanism reduced to tubercle on sternite 5 near anterior border. Penis sternal.
Pleon (Figs. 1C, 2D) relatively broad, outer surface smooth, lateral margins intermittently lined with short simple setae; pleonites 1 and 2 transversely wide, short; pleonite 3 widest, trapezoidal, with lateral margins convex, narrowing distally; pleonites 4–6 fused, sutures almost indiscernible; pleonite 4 subtrapezoidal, with lateral margins concave, narrowing distally, with noticeable concavity corresponding to produced sternal coaptation; pleonite 5 subquadrate, margins gently concave; pleonite 6 subtrapezoidal, lateral margins distinctly concave, broadening distally; gonopodal plate absent. Telson (Fig. 1C, 2D) covering posterior part of buccal cavity, wider than pleonite 6, with strongly convex lateral margins; distal margin medially shallowly concave.
G1 (Fig. 2A, B) long, laterally compressed, curving against sterno-pleonal surface; dorsal and ventral margins lined with numerous long, plumose setae; tip obscured by long, plumose setae, with shoulder at base of tubular distal process. G2 very short, with truncate tip.
Females. Thoracic sternum with vulva appearing on long, oblique bulge on sternite 6; operculum present near boarder with sternite 5. Pleon broad, greatest width less than half greatest width of thoracic sternum; lateral margins of somite 3 concave, those of somites 4–5 convex, those of somite 6 concave; distal margin of telson less concave than that in male.
Colour pattern. Somewhat variable. Carapace surface from pale yellowish with dirty grey-green mottling to mostly greenish brown with paler and darker areas. Eyes with dark grey cornea. Sternum pale yellow to greyish, sometimes with fine spotting. Chelipeds and ambulatory legs generally similar to carapace in colouration, more uniform ventrally, sometimes with fine spotting (Figs. 3, 4).
Etymology. The specific epithet derives from the region of the type locality of the new species, the Arabian Peninsula (Oman).
Distribution. Northwestern Indian Ocean: presently known only from two localities in northern Oman: Sur and Al-Sawadi (west of Muscat).
Ecology. Nearshore sandflats, at depths between 0 m and 1 m; in burrows of unknown hosts; syntopically collected infauna, including several specimens of callianassid ghost-shrimps and stomatopods (A. Anker, pers. obs.), is yet to be studied.
Remarks. Indopinnixa arabica n. sp. is morphologically most similar to I. haematosticta and I. kumejima in having the carapace more than twice as wide as long (Fig. 1A; Sakai 1934: fig. 3a; Naruse & Maenosono 2012: fig. 2a; Komai et al. 2022: fig. 3A, 7A, 10A). All other species of Indopinnixa have a proportionally narrower carapace (e.g., Barnard 1955: fig. 6a; Naruse & Maenosono 2012: fig. 4a; Ng 2014: fig. 3A; Ng & Rahayu 2022: fig. 2A). Indopinnixa arabica n. sp. differs from I. haematosticta and I. kumejima in the absence of a transverse carina on the cardiac region of the carapace (which is present in I. haematosticta and I. kumejima) (Fig. 2A; Sakai 1934: fig. 3a; Naruse & Maenosono 2012: figs. 1a, 2a; Komai et al. 2022: figs. 3A, 7A, 10A) and a tubular G1 with the terminal margin lacking a patch of dense, very short stiff setae on the distal half of the dorsal surface (which is present in I. haematosticta and I. kumejima) (Fig. 3A, B; Komai et al. 2022: figs. 5G, H, 10H, I; Naruse & Maenosono 2012, fig. 3b, c, tip of G1 incorrectly drawn, see Komai et al. 2022: 383, fig. 10H, I). Indopinnixa arabica n. sp. also has pleonites 4–6 fused and, importantly, with sutures almost indiscernible. In contrast, the sutures between these pleonites are clearly visible in I. kumejima and I. haematosticta (Naruse & Maenosono 2012: fig. 3a; Komai et al. 2022: figs. 2B, 5E).
Indopinnixa arabica n. sp. is presently the only identified species in its genus to have been reported from the Indian Ocean. Kazmi & Moazzam (2012) recorded a specimen from Gwadar, Pakistan, as Indopinnixa aff. sipunculana, although its small size (4/ 1 mm) and damaged condition did not allow accurate identification (Kazmi & Moazzam 2012: 1500). A record of Pinnixa penultipedalis from Mozambique by Barnard (1955) is noteworthy. The identity of the Mozambiquan specimen has been questioned before (Naruse & Maenosono 2012), and it shares some similarities with I. arabica n. sp. For instance, this specimen has pleonites 4–6 fused and the figure provided indicates that the sutures are not clearly demarcated (Barnard 1955: fig. 6a). Furthermore, although Barnard’s (1955: fig. 6h) figure is rather schematic, the G1 appears to be more similar to that of I. arabica n. sp. (Fig. 3A, B) than I. penultipedalis in its setation, tubular tip, and penultimate “shoulder”. Despite these similarities, however, the carapace of the Mozambiquan specimen is noticeably narrower (dimensions: 6.5 × 3.5 mm) and, at least according to Barnard’s (1955: fig. 6a) figure, has a less angular, more rounded anterolateral margin compared to that of I. arabica n. sp. (Figs. 1, 2A). Obviously, only a re-examination of Barnard’s specimen (if still extant) will elucidate its identity and confirm whether or not it represents I. arabica n. sp.
description: Published as part of Lasley Jr, Robert M., Anker, Arthur & Naruse, Tohru, 2024, Two new species and a new record of infaunal crabs (Decapoda: Brachyura: Pinnotheridae and Varunidae) from Oman and Saudi Arabia, pp. 207-229 in Zootaxa 5476 (1) on pages 209-214, DOI: 10.11646/zootaxa.5476.1.19, http://zenodo.org/record/12726911