Uroptychus shanei, 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 : 478-481

Uroptychus shanei n. sp.

Figures 239 , 240

TYPE MATERIAL — Holotype: Vanuatu. Boa 0 Stn CP 2307, 16°38.2’S, 167°58.2’E, 586-646 m, 14.XI.2004, 1 ♀ 5.3 mm ( MNHN-IU-2010-5481 ).

ETYMOLOGY„ Named for Shane T. Ahyong for his contributions to the knowledge of squat lobsters and for his willingness to read a draft of the manuscript of this paper.

DISTRIBUTION„ Vanuatu; 586- 646 m.

DESCRIPTION„ Small species. Carapace: 1.2 × broader than long (0.8 × as long as broad), broadest on posterior third; greatest breadth 1.8 × distance between anterolateral spines. Dorsal surface moderately convex from anterior to posterior, unarmed and sparingly covered with short fine setae. Lateral margins convex, without ridge on posterior portion; anterolateral spine small, slightly overreaching smaller lateral orbital spine; branchial margin with row of short setiferous ridges as to be seen as small crenulations in dorsal view. Rostrum straight horizontal, relatively broad triangular, with interior angle of 30°; dorsal surface flattish, lateral margin smooth; length half that of remaining carapace, breadth somewhat less than half carapace breadth at posterior carapace margin. Lateral orbital spine moderately remote from and located directly mesial to anterolateral spine. Pterygostomian flap smooth with sparse short fine setae on surface, anterior margin angular, ending in small spine.

Sternum: Excavated sternum with broadly convex anterior margin; surface smooth, without ridge and central spine. Sternal plastron 0.8 × as long as broad, lateral extremities convexly divergent posteriorly on sternites 4-6, subparallel on sternites 6-7. Sternite 3 shallowly depressed; anterior margin in broad V-shape without submedian spines, medially roundly excavated. Sternite 4 with anterolateral margin 1.5 × longer than posterolateral margin, anteriorly convex with obsolescent denticles. Anterolateral margin of sternite 5 anteriorly convex, 1.2 × longer than posterolateral margin of sternite 4.

Abdomen: Somite 1 without transverse ridge. Somite 2 tergite 3.4 × broader than long; pleural lateral margins concavely weakly divergent posteriorly, posterolateral end blunt. Pleuron of somite 3 with blunt lateral end. Telson half as long as broad; posterior plate 1.3 × longer than anterior plate, distinctly emarginate on posterior margin.

Eye: Short, 1.5 × longer than broad, not reaching midlength of rostrum; mesial and lateral margins subparallel. Cornea not dilated, half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 2.9 × longer than high. Antennal peduncle extending far beyond cornea, falling short of apex of rostrum. Article 2 distolaterally acuminate, without distinct spine. Antennal scale twice as broad as article 5, proportionately broad distally, distally blunt, reaching distal end of article 5, greatly overreaching eye. Articles 4 and 5 unarmed; article 5 1.4 × longer than article 5, breadth slightly more than half height of antennular ultimate article. Flagellum of 12 segments ending in distal margin of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 with relatively long fine setae other than brushes on distal articles. Basis with mesial ridge lobe-like, without denticles. Ischium with flexor margin not rounded distally; crista dentata with about 30 minute denticles. Merus 2 × longer than ischium, distally broader in lateral view, distolateral spine small but distinct; flexor margin moderately ridged, with 2 small spines on distal quarter. Carpus unarmed.

P1: 4.4 × longer than carapace, covered with long, fine, soft setae arising from short ridges. Ischium with short blunt dorsal spine, ventromesially with rudimentary denticles, without distinct subterminal spine. Merus with small blunt spines along mesial margin, slightly shorter than carapace. Carpus 1.1 × longer than merus, unarmed. Palm 2.6 × longer than broad, 1.2 × longer than carpus. Fingers moderately depressed, distally incurved, crossing when closed; fixed finger with low process at midlength of opposable margin; movable finger half as long as palm, opposable margin with obtuse proximal process.

P2-4: Relatively broad and moderately compressed mesio-laterally, with fine soft setae. Meri slightly shorter on P3 than on P2, shorter on P4 than on P3 (P4 merus 0.8 × length of P3 merus); breadths slightly smaller on P4 than on P2 and P3; length-breadth ratio, 4.0 on P2, 3.8 on P3, 3.2 on P4; dorsal margins proximally irregular with obsolescent eminences, distally unarmed. P2 merus 0.7 × as long as carapace, as long as P2 propodus; P3 merus 0.9 × length of P3 propodus; P4 merus 0.8 × length of P4 propodus. Carpi subequal on P2 and P3, slightly shorter on P4; carpus-propodus length ratio, 0.6 on P2, 0.5 on P3 and P4. Propodi longest on P3, shortest on P2; flexor margin somewhat convex on distal portion, ending in pair of terminal spines preceded by 6 spines on P2 (proximal-most remote from proximal second and situated somewhat proximal to midlength), 3 spines on P3 and P4 (situated on distal third). Dactyli 0.4 × as long as propodi on P2-4, dactylus-carpus length ratio, 0.7 on P2, 0.8 on P3, 1.0 on P4; flexor margin moderately curving, distally ending in strong spine preceded by 5-6 elongate triangular, loosely arranged and proximally diminishing spines, penultimate spine more remotely separated from ultimate than from antepenultimate by twice distance between penultimate and antepenultimate.

REMARKS — The new species resembles U. plumella n. sp. and U. senticarpus n. sp. (see under U. plumella for their similarities). Uroptychus shanei is distinctive in the shape and spination of the P2-4 dactyli and in the spination of the P1 carpus; the dactyli are more sharply tapering distally, with the penultimate of the flexor marginal spines more remote from the ultimate than from the antepenultimate, separated by twice instead of equal distance between the penultimate and antepenultimate spines; the P1 carpus is unarmed instead of bearing a spine at midpoint of the distodorsal margin. In addition, the antenna is different from one another; the antennal article 2 is distolaterally acuminate without distinct spine in U. shanei and U. plumella , bearing a small spine in U. senticarpus ; the antennal articles 4 and 5 are unarmed in U. shanei , whereas these articles bear a tiny spine in U. plumella , a distinct spine in U. senticarpus ; the antennal scale is distally blunt or rounded, terminating at the distal end of article 5 in U. shanei , whereas it tapers to a sharp point, extending far beyond article 5 in U. plumella and U. senticarpus . The anterolateral spine of the carapace is different in direction: directed straight forward in U. plumella , anteromesially in U. shanei , and anterolaterally in U. senticarpus .

Figures

FIGURE 239 Uroptychus shanei n. sp., holotype, female 5.3 mm (MNHN-IU-2010-5481). A, carapace and anterior part of abdomen, proximal part of left P1 included, dorsal. B, same, lateral.C, sternal plastron, with excavated sternum and basal parts of Mxp1. D, telson. E, right antenna, ventral.F, right Mxp3, ventral.G, same, ventral.H, left P1, setae on fingers and palm omitted, dorsal. I, same, proximal part, setae omitted,ventral. Scale bars: 1 mm.

FIGURE 240 Uroptychus shanei n. sp., holotype, female 5.3 mm (MNHN-IU-2010-5481). A, left P2, lateral. B, same, distal part, setae omitted, lateral. C, left P3, setae omitted, lateral.D, left P4, setae omitted,lateral.Scale bars:1 mm.