Uroptychus senarius, Baba, 2018

Baba, Keiji, 2018, Chirostylidae of the Western and Central Pacific: Uroptychus and a new genus (Crustacea: Decapoda: Anomura), Tropical Deep-Sea Benthos (Mémoires du Muséum national d'Histoire naturelle 212), pp. 1-612 : 462-466

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Uroptychus senarius

n. sp.

Uroptychus senarius n. sp.

Figures 231 View FIGURE 231 , 232 View FIGURE 232 , 306B View FIGURE 306

TYPE MATERIAL — Holotype: New Caledonia, Norfolk Ridge. SMIB 5 Stn DW103, 23°16’S, 168°04’E, 300-315 m, 14.IX.1989, ov. ♀ 4.5 mm ( MNHN-IU-2014-16944 ) GoogleMaps . Paratypes: Solomon Islands. SALOMON 2 Stn DW2301, 9°06.9’S, 158°20.6’E, 267-329 m, 8.XI.2004, 1 ov. ♀ 6.2 mm (MNHN-IU-2014-16945) . Vanuatu. MUSORSTOM 8 Stn CP1024, 17°48.21’S, 168°38.77’E, 335-370 m, 28.IX.1994, 1 ov. ♀ 4.9 mm (MNHN-IU-2014-16946) .

ETYMOLOGY„ From the Latin senarius (consisting of six), referring to six spines on the rostrum (three spines on each lateral margin).

DISTRIBUTION„ Solomon Islands, Vanuatu and Norfolk Ridge; 267- 370 m.

SIZE„ Ovigerous females, 4.5-6.2 mm; no males were collected.

DESCRIPTION„ Medium-sized species. Carapace: 1.2 × broader than long (0.8 × as long as broad); greatest breadth 1.6 × distance between anterolateral spines. Dorsal surface somewhat convex from anterior to posterior, with distinct depression between gastric and cardiac regions, and shallower depression between cardiac and branchial regions; with large, slender upright spines and scattered small spines. Lateral margins slightly convexly divergent posteriorly, with row of strong sharp spines; anterolateral spine overreaching lateral orbital spine. Rostrum relatively broad triangular, distally curving dorsally, with 3 pairs of antero-dorsally directed lateral spines; dorsal surface flattish; length 1.4 × breadth, slightly more than half length of carapace, breadth slightly less than half carapace breadth at posterior carapace margin. Lateral orbital spine much smaller than and distinctly anterior to level of anterolateral spine. Pterygostomian flap covered with small spines, anteriorly roundish and produced to sharp spine.

Sternum: Excavated sternum strongly cristate in midline, narrowly produced anteriorly. Sternal plastron 0.9 × as long as broad, lateral extremities between sternites 4-7 straight divergent. Sternite 3 well depressed, anterior margin in broad V-shape with 2 submedian spines separated by V-shaped notch, anterolaterally sharp angular, flanked by small spine. Sternite 4 with 2 well-developed, anteroventrally directed spines on anterolateral margin, distal spine smaller, situated at anterior end; posterior surface with scattered granules supporting relatively thick setae; posterolateral margin as long as anterolateral margin. Sternite 5 with well-developed anterolateral spine, lateral margin posteriorly divergent, distinctly shorter than posterolateral margin of sternite 4. Abdomen: Somite 1 with 4 strong spines in transverse row and a few additional small spines. Somite 2 tergite 2.2- 2.5 × broader than long; pleuron anterolaterally produced and angular, posterolaterally strongly produced and tapering to sharp point; lateral margin strongly convex and strongly divergent posteriorly. Pleuron of somite 3 also tapering to sharp point. Somites 2-4 with 2 transverse rows of well-developed spines: 6 anterior and 5-8 posterior spines on each of somites 2 and 3, 4 anterior and 2-4 posterior spines on somite 4. Somites 5 and 6 with fine granules supporting setae. Somite 5 with 2-4 anterior and 0-2 posterior spines. Somite 6 unarmed. Uropod having protopod smooth along margins; endopod 1.4 × longer than broad. Telson 0.5-0.6 × as long as broad; posterior plate 1.1-1.3 × longer than anterior plate, distinctly emarginate on posterior margin.

Eye: 2 × as long as broad, slightly overreaching midlength of rostrum, proximally broadened, constricted proximal to cornea. Cornea narrower than and more than half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 3.2-3.5 × longer than high. Antennal peduncle extending far beyond eye, falling short of apex of rostrum. Article 2 with strong lateral spine. Antennal scale 1.6 × broader than article 5, terminating in or slightly overreaching midlength of article 5; lateral margin with several broad setae. Article 3 with distinct distomesial spine and small ventral spine near juncture with article 4. Article 4 with strong distomesial spine and smaller ventromesial spine at midlength. Article 5 slightly shorter than article 4, with well-developed distomesial spine and 1-2 smaller ventromesial spines; breadth 0.6 × height of antennular ultimate article. Flagellum of 7-9 segments overreaching rostrum by proximal 3-4 segments, far falling short of distal end of P 1 merus.

Mxp: Mxp1 with bases close to each other but not contiguous. Mxp3 with strong distolateral spine on each of coxa, ischium, merus and carpus. Basis without denticles on mesial ridge. Ischium with 1 or 2 spines close to distolateral spine; crista dentata with distally diminishing denticles. Merus 1.7 × longer than ischium, with 3-4 spines along flexor margin and strong distolateral spine; extensor margin with very small or moderate-sized distal spine. Carpus with 2 spines on extensor surface.

P 1: 4.5 × longer than carapace, with sparse short setae; 9 rows of spines on merus continued on to palm (3 dorsal, 2 lateral, 2 mesial, 2 ventral). Ischium with well-developed dorsal spine and prominent subterminal spine on ventromesial margin. Merus 1.1-1.2 × length of carapace. Carpus 1.1 × length of merus. Palm 3.0-3.3 × longer than broad, slightly shorter than carpus. Fingers broad relative to length, distally crossing when closed. Movable finger 0.5-0.6 × length of palm; opposable margin with low median process; mesial margin with small spines on proximal half; fixed finger with obsolescent spines on proximal lateral margin, sinuous on opposable margin.

P 2-4: Subcylindrical, with rows of spines. Meri successively shorter posteriorly ( P 3 merus 0.94-0.95 × length of P 2 merus, P 4 merus 0.8-0.9 × length of P 3 merus), equally broad on P 2-4; P 2 merus subequal to or slightly shorter than carapace, subequal to or slightly longer than P 2 propodus; P 3 merus 0.9-1.0 × [0.8 × on female paratype MNHN-IU-2014-16457] length of P 3 propodus; P 4 merus 0.8-0.9 × length of P 4 propodus; length-breadth ratio, 5.8- 6.1 on P 2, 5.0-5.7 on P 3, 4.6-4.7 on P 4; 5 rows of spines (dorsal and ventrolateral rows of strong spines, 2 lateral and 1 ventromesial row of small spines) continued on to carpus. Carpi subequal, longer than dactyli (carpus-dactylus length ratio, 1.3-1.5 on P 2, 1.2-1.4 on P 3, 1.1-1.3 on P 4); carpus-propodus length ratio, 0.5 on P 2, 0.4-0.5 on P 3, 0.4 on P 4. Propodi subequal on P 3 and P 4, shortest on P 2; extensor margin with row of spines accompanying subparalleling row of fewer spines laterally and mesially; flexor margin straight, with pair of terminal spines preceded by row of spines (distal 5 in zigzag arrangement). Dactyli shorter than carpi (dactylus-carpus length ratio, 0.7-0.8 on P 2, 0.7-0.9 on P 3, 0.8-1.0 on P 4); dactylus-propodus length ratio, 0.4 on P 2-3, 0.3-0.4 on P 4; flexor margin slightly curving, with row of 9-10 sharp spines subperpendicular to margin, ultimate smaller than penultimate and subequal to antepenultimate and remainder.

Eggs. Number of eggs carried, 3-17; size, 1.06 mm × 1.02 mm - 1.12 mm × 1.23 mm.

Color. Ovigerous female from Vanuatu (MNHN-IU-2014-16946): Base color translucent bluish gray to pale pink, pereopods with dark orange bands on meri, carpi and propodi.

REMARKS„ The following six species are grouped together by the noticeably spinose carapace and pereopods, and the arrangement of spines on the P 2-4 dactyli (the ultimate spine preceded by subperpendicularly or obliquely directed, proximally diminishing spines), and the sternite 3 anterior margin bearing two submedian spines separated by a notch or sinus: Uroptychus ciliatus ( Van Dam, 1933) , U. numerosus n. sp., U. quartanus n. sp., U. senarius n. sp., U. spinirostris ( Ahyong & Poore, 2004) , and U. spinimanus Tirmizi, 1964 . Uroptychus chacei ( Baba, 1986b) looks very close to this group but is different in having no submedian spines and no median notch on the anterior margin of sternite 3. Within this group, Uroptychus spinimanus keys out first by having no spine on the abdomen and no strong spine on the lateral margin of sternite 4. Uroptychus numerosus differs from the other species in having an elongate, distally broad (not tapering) rostrum with more numerous spines (9 versus 1-5). Uroptychus ciliatus differs from U. spinirostris , U. quartanus and U. senarius in having the ultimate of the flexor marginal spines of P 2-4 dactyli, which is subequal to or slightly larger than instead of more slender than the penultimate. Uroptychus spinirostris differs from U. quartanus and U. senarius in having a relatively long rostrum (the length being three-quarters instead of at most slightly more than half that of the carapace) and more spinose abdominal somites, especially somites 6 that bears numerous spines instead of no spine.

Uroptychus senarius is distinguished from U. quartanus by the sternal plastron that is successively broader posteriorly instead of broadest on sternite 4 and subequally broad on sternites 5-7; the ventral surface of sternite 4 has scattered granules and relatively thick setae instead of a row of denticles arranged in a concentric arc and fine setae; the abdominal somite 1 bears a row of four strong spines instead of three spines; the abdominal somite 3-5 bear two transverse (anterior and posterior) rows of spines instead of an anterior row only; the antennal scale terminates in the midlength of article 5 rather than reaching the end of that article; the crista dentata of Mxp3 bears a row of distally diminishing, numerous, closely arranged spines instead of loosely arranged, less numerous spines; the posterior plate of the telson is distinctly emarginate instead of subsemicircular on the posterior margin.

The three pairs of lateral rostral spines as possessed by U. senarius are also known in the larger male of U. spinirostris reported by McCallum & Poore (2013) from western Australia, which usually bears two pairs of spines (see above). However, the rostrum in U. senarius is broader relative to length (length-breadth ratio, about 1.5 versus more than 2.0). Also, sternite 4 in this new species is spineless on the ventral surface instead of bearing one or two pairs of spines.

The ovigerous female from MUSORSTOM 8 Stn CP1024 (MNHN-IU-2014-16946) is somewhat different from the others: the rostrum bears two lateral spines on each side and an additional small spine proximal to the right proximal spine; the P 2-4 meri are relatively broad compared to those of the other specimens, with the length-breadth ratio, 5.0 on P 2, 4.8 on P 3 and 4.0 on P 4, versus 5.8-6.1 on P 2, 5.4-5.7 on P 3, 4.6-4.7 on P 4 in the other specimens; and P 3 merus is relatively short (it is as long as P 3 propodus, 0.8 times as long in the other specimens). This specimen is provisionally placed in U. senarius until more material becomes available.