Uroptychus latior, 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 : 259-264

Uroptychus latior n. sp.

Figures 119 , 120

TYPE MATERIAL — Holotype: New Caledonia, Chesterfield Islands . CORAIL 2 Stn DE 14, 21°00.69’S, 160°57.18’E, 650- 660 m, 21.VII.1988, ♀ 6.1 mm ( MNHN-IU-2012-682 ) (with rhizocephalan externa on abdomen).

ETYMOLOGY„ From the Latin latior (broader), alluding to the carapace breadth being distinctly greater than that of the close relative U. edisonicus Baba & Williams, 1998 .

DESCRIPTION„ Small species. Carapace: 0.7 × as long as broad, broadest on posterior fourth; greatest breadth 2.3 × distance between anterolateral spines. Dorsal surface strongly convex from anterior to posterior and from side to side, without depression bordering gastric and cardiac regions, covered with minute pits suggesting supporting fine setae. Lateral margins convexly divergent, finely granulose, and weakly ridged along posterior fourth; anterolateral spine short, moderately remote from and overreaching lateral orbital angle, directed somewhat mesially. Rostrum horizontal, narrow triangular, with interior angle 25°; dorsal surface nearly flattish; lateral margin straight with 3 (left) or 2 (right) spinules or denticle-like small spines distally; length half that of remaining carapace, breadth one-third carapace breadth at posterior carapace margin. Lateral orbital angle acuminate, located at level of anterolateral spine. Pterygostomian flap smooth on surface, anterior margin angular, produced to small spine.

Sternum: Excavated sternum with slightly convex anterior margin; surface with weak ridge in midline. Sternal plastron 0.7 × as long as broad, lateral extremities divergent posteriorly. Sternite 3 shallowly depressed; anterior margin deeply excavated in semicircular shape without median notch and spines. Sternite 4 with anterolateral margin anteriorly convex and denticulate, about 2 × longer than posterolateral margin. Anterolateral margin of sternite 5 anteriorly convex and denticulate, 1.5 × longer than posterolateral margin of sternite 4.

Abdomen: Somite 1 somewhat convex from anterior to posterior, without transverse ridge. Somite 2 tergite 2.8 × broader than long; pleural lateral margins concavely divergent posteriorly, posterolateral end blunt. Pleuron of somite 3 with blunt posterolateral margin. Telson 0.4 × as long as broad; posterior plate slightly longer than anterior plate, concave on posterior margin.

Eye: 1.5 × longer than broad, distally narrowed, not reaching midlength of rostrum; cornea not dilated, slightly shorter than remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 3.8 × longer than high. Antennal peduncle overreaching cornea, reaching midlength of rostrum. Article 2 with small lateral spine. Antennal scale ending in blunt tip, 2.2 × broader than article 5, extending far beyond eye and reaching end of proximal third segment of flagellum. Articles 4 and 5 each with tiny distomesial spine; article 5 1.3 × longer than article 5, breadth 0.6 × height of antennular ultimate article. Flagellum of 14 segments slightly falling short of distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 with relatively long plumose fine setae other than brushes on distal articles. Basis with a few obsolescent denticles on mesial ridge. Ischium with flexor margin not rounded distally; crista dentata with ca. 30 distally diminishing denticles. Merus 2.2 × longer than ischium, flexor margin roundly ridged, with 2 tiny spines or processes distal to point one-third from distal end; distolateral spine small on merus, obsolescent on carpus.

P1: 4.7 × longer than carapace, sparingly covered with relatively short fine plumose setae. Ischium with small dorsal spine, ventromesial margin with row of denticle-like spines, subterminal spine vestigial. Merus finely and sparsely granulose on surface, with small distomesial and distolateral spines on ventral surface, and row of denticles along distodorsal margin; length subequal to that of carapace. Carpus subcylindrical, 1.3 × longer than merus, distodorsal margin with row of denticles. Palm 4.1 × longer than broad, 1.1 × longer than carpus. Fingers moderately depressed and relatively broad, distally incurved, crossing when closed, not gaping; fixed finger with low eminence at midlength of opposable margin; movable finger half as long as palm, opposable margin with low proximal process fitting to longitudinal groove on opposable face of fixed finger when closed.

P2-4: Relatively broad and somewhat compressed mesio-laterally, with fine soft setae. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.7 length of P3 merus); breadths greatest on P3, smaller and subequal in P2 and P4; length-breadth ratio, 4.1 on P2, 3.5 on P3, 2.7 on P4; dorsal margins rounded, not cristiform, with 2 tiny proximal spines on P2 and P3, smooth on P4. P2 merus 0.8 × as long as carapace, 1.1 × length of P2 propodus; P3 merus 0.9 × length of P3 propodus; P4 merus 0.7 × length of P4 propodus. Carpi successively shorter posteriorly; carpus-propodus length ratio, 0.6 on P2, 0.5 on P3, 0.4 on P4; extensor margins with small but distinct proximal spine on P2-4. Propodi longest on P3, shorter and subequal on P2 and P4; flexor margin strongly convex on distal portion, ending in pair of terminal spines preceded by 8, 7, 6 spines on P2, P3, P4 respectively. Dactyli shortest on P2, subequal on P3 and P4; moderately curving; dactylus-carpus length ratio, 0.8 on P2, 1.0 on P3, 1.2 on P4; dactylus-propodus length ratio, 0.4 on P2 and P3, 0.5 on P4; flexor margin with 8 strong, subtriangular spines more or less closely arranged, proximally diminishing, and obliquely directed on P2-4.

PARASITES — A rhizocephalan externa on the abdomen.

REMARKS — The combination of the following characters links the species to U. edisonicus Baba & Williams, 1998 , U. norfolkanus n. sp. and U. pedanomastigus n. sp.: the carapace broader than long, bearing an anterolateral spine only on the lateral margin; sternite 3 with a deeply excavated, semicircular anterior margin; P1 almost spineless, with the fingers strongly incurved distally; the P2-4 propodi distally broadened, and dactyli ending in a strong spine preceded by similar but proximally diminishing spines. Uroptychus latior differs from U. edisonicus ( Figure 121 ) in having the carapace much broader (length-breadth ratio 0.7 versus 0.8), in having the anterolateral spine of the carapace directed anteromesially instead of straight forward, in having the antennal scale extending far beyond instead of terminating at the tip of the antennal article 5 (extending far beyond instead of slightly overreaching the eyes), in having the pterygostomian flap anteriorly ending in a small spine instead of being produced to a larger spine, and in having the P2-4 dactyli with obliquely instead of perpendicularly directed flexor marginal spines. The relationships with U. norfolkanus and U. pedanomastigus are discussed under the accounts of the respective species (see below).

Figures

FIGURE 119 Uroptychus latior n. sp., holotype, female 6.1 mm (MNHN-IU-2012-682). A, carapace and anterior part of abdomen, proximal part of left P1 included, fine setae omitted, 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.H, same, lateral. Scale bars: 1 mm.

FIGURE 120 Uroptychus latior n. sp.,holotype,female 6.1 mm (MNHN-IU-2012-682).A, left P1, proximal part, setae omitted,ventral.B, same,distal articles,dorsal. C, same,fingers, ventral. D, left P2, lateral. E, same, distal part,setae omitted, lateral.F, left P3, setae omitted, lateral.G, left P4, setae omitted,lateral, H, same,distal part,setae omitted,lateral. Scale bars:1 mm.

FIGURE 121 Uroptychus edisonicus Baba& Williams,1998,holotype,ovigerous female 4.6 mm,USNM 251479.A, anterior part of carapace,dorsal.B, anterior part of sternal plastron,excavated sternum and basal parts of Mxp1 included.C, left Mxp3,crista dentata,ventral.D, right P2,setae omitted,lateral.E, same, distal part, setae omitted.F, right P3,lateral.G, same, distal part, lateral.H, right P4,lateral.Scale bars:A,B, D-H,1 mm; C,0.5 mm.