Uroptychus tafeanus, 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 : 510-513

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Uroptychus tafeanus

n. sp.

Uroptychus tafeanus n. sp.

Figures 256 View FIGURE 256 , 257 View FIGURE 257

TYPE MATERIAL — Holotype: Vanuatu. MUSORSTOM 8 Stn CP 974, 19°22’S, 169°28’E, 492-520 m, 22.IX.1994, ov. ♀ 4.3 mm ( MNHN-IU-2012-680 ) GoogleMaps . Paratype: Station data as for the holotype, 1 ♂ 4.7 mm (MNHN-IU-2013-8511) .

ETYMOLOGY„ From Tafea, one of the six provinces of Vanuatu from which the species was found, and the Latin suffix anus (belonging to).

DISTRIBUTION„ Vanuatu, 492- 520 m.

DESCRIPTION„ Small species. Carapace: Broader than long (0.8 × as long as broad), broadest on posterior third; greatest breadth 2.0-2.1 × distance between anterolateral spines. Dorsal surface strongly convex from anterior to posterior, smoothly sloping down to rostrum, sparsely with short fine setae. Lateral margins convexly divergent posteriorly (divergent posteriorly to point one-third from posterior end, and then convergent), granulate, weakly ridged along posterior sixth of length; anterolateral spine strong, directly slightly mesially, overreaching lateral orbital spine. Rostrum somewhat deflected ventrally, relatively narrow triangular, with interior angle 20-22°; dorsal surface feebly concave, length slightly more than half (0.54-0.58) that of remaining carapace, breadth about one-third carapace breadth at posterior carapace margin. Lateral orbital spine small, situated at level of anterolateral spine and separated from that spine by its basal breadth. Pterygostomian flap smooth on surface, anterior margin angular, produced to distinct spine.

Sternum: Excavated sternum with broadly convex anterior margin; surface smooth, with or without weak low ridge in midline. Sternal plastron‰.7-0.8 × as long as broad, lateral extremities convexly divergent posteriorly; broadest on sternite 7. Sternite 3 shallowly depressed; anterior margin in broad V-shape without submedian spines, medially roundly excavated. Sternite 4 with anterolateral margin more than 2 × longer than posterolateral margin, anteriorly convex with obsolescent denticles. Anterolateral margin of sternite 5 convexly divergent posteriorly, 1.6-1.7 × longer than posterolateral margin of sternite 4.

Abdomen: Somite 1 weakly convex from anterior to posterior, without transverse ridge. Somite 2 tergite 3.2 × broader than long; pleural lateral margin concavely divergent posteriorly, posterolateral end blunt. Pleuron of somite 3 with blunt posterolateral terminus. Telson 0.4 × as long as broad; posterior plate about as long as anterior plate, distinctly emarginate on posterior margin.

Eye: Short, 1.5 × longer than broad, not reaching midlength of rostrum, distally narrowed, lateral and mesial margins convex. Cornea more than half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 3.0-3.3 × longer than high. Antennal peduncle extending far beyond cornea, reaching midlength of rostrum. Article 2 with small lateral spine. Antennal scale tapering, 2.4 × broader than article 5, reaching distal end of proximal third segment of flagellum, extending forward far beyond eye. Articles 4 and 5 each with distinct distomesial spine, article 5 1.3-1.5 × longer than article 5, breadth about half height of antennular ultimate article. Flagellum of 13 segments overreaching apex of rostrum, not reaching distal margin of P 1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 with relatively long fine setae other than brushes on distal articles. Basis having mesial ridge lobe-like, smooth or with obsolescent denticle. Ischium with flexor margin not rounded distally; crista dentata with numerous small denticles. Merus twice as long as ischium, with small distolateral spine; flexor margin ridged, with 2 or 3 small spines on distal third. Carpus also with small distolateral spine.

P 1: 4.7-4.8 × longer than carapace, covered with scattered short ridges supporting short fine soft setae. Ischium with short blunt dorsal spine, ventromesial margin denticulate, without subterminal spine. Merus with 2 small spines on proximal part of mesial margin, length subequal to or slightly more than that of carapace. Carpus 1.3 × longer than merus, dorsal surface with 4 small protuberances transversely arranged near juncture with merus. Palm 2.9-3.0 × longer than broad, 1.3 × longer than carpus. Fingers moderately depressed, distally incurved, gaping in distal half in male paratype, not gaping in female holotype; fixed finger with blunt triangular process at midlength of opposable margin; movable finger 0.4 × as long as palm, opposable margin with median process proximal to position of opposite process of fixed finger; ventral face of fixed finger with longitudinal groove accommodating opposite process of movable finger when closed.

P 2-4: Relatively broad and somewhat compressed mesio-laterally, with fine soft setae. Meri successively shorter posteriorly ( P 3 merus 0.8-0.9 × length of P 2 merus, P 4 merus 0.7 × length of P 3 merus); breadths subequal on P 2 and P 3 or slightly smaller on P 3 than on P 2, smallest on P 4 ( P 4 merus 0.8-0.9 × breadth of P 3 merus); length-breadth ratio, 3.1-3.4 on P 2, 2.9 on P 3, 2.3-2.5 on P 4; dorsal margin rounded, not crested and unarmed; P 2 merus 0.7-0.8 × as long as carapace, subequal to length of P 2 propodus; P 3 merus‰.9-1.0 × length of P 3 propodus; P 4 merus‰.7 × length of P 4 propodus. Carpi successively shorter posteriorly or subequal on P 2 and P 3, much shorter on P 4; carpus-propodus length ratio, 0.5 on P 2 and P 3, 0.4 on P 4; carpus-dactylus length ratio, 1.2 on P 2, 1.1 on P 3, 0.9 on P 4. Propodi successively shorter posteriorly or subequal on P 2 and P 3 and shorter on P 4; flexor margins slightly convex on distal portion, ending in pair of terminal spines preceded by 5 movable spines on P 2, 4 or 5 on P 3, 3 on P 4 (restricted to distal third of length). Dactyli 0.4 × as long as propodi on P 2 and P 3, 0.5 × on P 4; dactylus-carpus length ratio, 0.8 on P 2, 0.9 on P 3, 1.1 on P 4; flexor margins slightly curving, with 9, 9 or 10, 9-11 somewhat obliquely directed, proximally diminishing, triangular spines on P 2, P 3, P 4 respectively, ultimate slightly narrower than penultimate.

Eggs. Ten eggs carried; size, 1.00 × 1.22 mm - 1.00 × 1.27 mm.

Color (in preservative). Reddish stripe in midline of carapace as broad as rostrum, extending on to somite 6 of abdomen; similar stripe on each side of carapace but not clear on abdomen; in female, median stripe broadened on gastric region where connecting to side stripes.

REMARKS„ The species resembles U. plumella n. sp., U. senticarpus n. sp., and U. shanei n. sp. (see above under the accounts of these species for their similarities). From all of these congeners U. tafeanus is readily distinguished by the ultimate flexor marginal spine of the P 2-4 dactyli that is somewhat smaller instead of distinctly larger than the penultimate, hence these two groups are remote from each other in the key to species (see above). Uroptychus tafeanus is closer to U. senticarpus , from which it is distinguished by the anterolateral spine of the carapace directed anteromesially instead of anterolaterally; the distodorsal margin of the P 1 carpus is unarmed instead of bearing a distinct spine at the midpoint of the distodorsal margin; and the P 2-4 carpi are unarmed instead of bearing a small proximal spine on the extensor margin.