Uroptychus numerosus, 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 : 359-362

Uroptychus numerosus n. sp.

Figures 176 , 177

TYPE MATERIAL — Holotype: New Caledonia. BIOGEOCAL Stn DW 307, 20°35.38’S, 166°55.25’E, 470-480 m, 1.V.1987, ♂ 4.1 mm ( MNHN-IU-2014-16830 ) . Paratype: Station data as for the holotype, 1 ov. ♀ 4.3 mm (MNHN-IU-2014-16831).

ETYMOLOGY — From the Latin numerosus (many), referring to numerous spines on the rostral lateral margin, the character to separate the species from related species.

DISTRIBUTION„ New Caledonia; 470- 480 m.

DESCRIPTION„ Small species. Carapace: As long as broad; greatest breadth 1.6 × distance between anterolateral spines. Dorsal surface covered with numerous, sharp, slender spines, slightly convex in profile, with depression bordering gastric and cardiac regions. Lateral margins convex along branchial regions; anterolateral spine overreaching lateral orbital spine. Rostrum straight, directed slightly dorsally, long and narrow but proportionately broad distally, with interior angle of ca. 10°, bearing 9 dorso-anteriorly directed spines along entire lateral margin, and pair of small spines on basal part of dorsal surface; length 0.8 × that of remaining carapace, breadth much less than half carapace breadth at posterior carapace margin. Pterygostomian flap covered with small spines, anteriorly somewhat roundish, produced to strong spine.

Sternum: Excavated sternum sharply cristate in anterior midline, anterior margin convex. Sternal plastron slightly longer than broad; sternites 4-6 successively slightly broader posteriorly, sternite 7 slightly narrower than sternite 6. Sternite 3 depressed well, anterior margin deeply excavated in semicircular shape, with 2 submedian spines separated by U-shaped sinus and flanked by small spine on surface. Sternite 4 with small spines arranged in posteriorly concentric arcs on posterior surface; anterolateral margin short, 0.7 × as long as posterolateral margin, with 2 strong spines, one at anterior terminus, another at midlength. Sternite 5 with 1 or 2 anterolateral spines, length about half that of posterolateral margin of sternite 4.

Abdomen: Somite 1 with anterior row of 3 spines (right one missing in holotype) and posterior row of 6 spines. Somite 2 tergite 2.2 × broader than long; pleuron anterolaterally sharply produced, posterolaterally strongly produced and tapering to sharp point; pleural lateral margins strongly concave and strongly divergent posteriorly; tergite with spines arranged roughly in 3 rows: anterior row of 8 spines, median row of 4 or 5 spines, posterior row of 6-7 spines. Somite 3 with spines roughly arranged in 3 rows: anterior row of 6-8 spines, median row of 8 spines, posterior row of 4-10 spines. Somite 4 with 3 rows of spines (4-7 anterior, 6-10 median, 8-16 posterior); pleura of somites 3 and 4 tapering laterally to sharp point. Somite 5 with 16-25 spines roughly in 3 rows. Somite 6 with 26-30 spines more or less transversely arranged on surface and 7 spines along posterior margin. Telson 0.5 × as long as broad; posterior plate 1.6-1.7 × longer than anterior plate, not emarginate on posterior margin. Uropod having protopod with small, elongate, distally blunt projection on mesial margin; endopod 2.2 × longer than broad.

Eye: Globular, short relative to breadth, 1.3-1.4 × longer than broad, convex on mesial margin, terminating at most in proximal quarter of rostrum. Cornea narrower than greatest breadth of eyestalk, slightly shorter than remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 3.5-3.6 × longer than high. Antennal peduncle extending far beyond cornea. Article 2 with sharp lateral spine. Article 3 with distinct mesial spine. Antennal scale as broad as article 5, overreaching midlength of, but not reaching distal end of article 5. Article 4 with strong distomesial spine and additional small spine at midlength of mesial margin. Article 5 1.4 × longer than article 4, with distomesial and distolateral spines (both much smaller than distomesial spine of article 4) plus 2 mesial marginal spines; breadth 0.5 × height of ultimate antennal article. Flagellum consisting of 6 segments, terminating in apex of rostrum, not reaching distal end of P1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 coxa with strong ventrolateral spine. Basis with a few obsolescent denticles on mesial ridge. Ischium with strong distolateral spine (accompanying small spine directly mesial to it in paratype); flexor margin distally not rounded; crista dentata with 7-11 distally diminishing denticles, proximal denticles loosely arranged. Merus twice as long as ischium, with 5-6 flexor marginal, 2 lateral (including strong distal spine) and 2 extensor marginal spines. Carpus with 3 extensor marginal and 3 lateral spines.

P1: 5.5-6.5 × length of carapace, sparsely setose. Ischium with strong dorsal and strong ventromesial subterminal spine. Merus 1.2-1.4 × carapace length, surface covered with spines in 8 rows (2 dorsal, 2 lateral, 2 ventral, 2 mesial) continued on to carpus and palm. Carpus 1.3-1.4 × length of merus. Palm 5.3-5.6 × longer than broad, as long as carpus. Fingers distinctly gaping in male, slightly gaping in female, ending in incurved spine, crossing when closed; fixed finger with low eminence distal to midlength of opposable margin, bearing row of small spines on proximal half of lateral margin, and small spines on proximal part of dorsal surface; movable finger 0.4 × length of palm; opposable margin with prominent median process fitting to longitudinal groove on opposite face of fixed finger when closed; lateral margin with row of spines.

P2-4: Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.9 × length of P3 merus), broader on P4 than on P2 and P3; length-breadth ratio, 5.4-5.5 on P2, 4.7-4.8 on P3, 3.8-4.0 on P4; dorsal row of strong spines (ca. 8 in number) interspaced by smaller spines, 3 rows of lateral spines small on P2-3, relatively large on P4, 3 rows of ventral spines (ventrolateral larger), all these rows continued on to carpus and propodus (not on flexor margin); P2 merus subequal to carapace length, 1.2 × length of P2 propodus; P3 merus 1.1 × length of P3 propodus; P4 merus 0.9 × length of P4 propodus. Carpi subequal; carpus-propodus length ratio, 0.6 on P2 and P3, 0.5 on P4; carpus-dactylus length ratio, 1.2-1.4 on P2, 1.0-1.4 on P3, 1.3 on P4. Propodi subequal in length on P2-3, longer on P4; flexor margin straight, with pair of terminal movable spines preceded by row of spines, distal 4-7 spines in zigzag arrangement and others in straight line. Dactyli shorter than carpi (dactylus-carpus length ratio, 0.7 on P2, 0.7 on P2, 0.8 on P4), 0.4 × as long as propodi on P2-4; flexor margin slightly curving, with 8 or 9 somewhat oblique, proximally diminishing spines on P2 and P3, 9 or 10 spines on P4, ultimate somewhat narrower than penultimate.

Eggs. Number of eggs carried, 6; size, 1.00 mm × 1.40 mm - 1.06 mm × 1.42 mm; eggs postembryonic.

REMARKS — The new species is grouped together with U. ciliatus ( Van Dam, 1933) , U. quartanus n. sp. U. senarius n. sp., U. spinimanus Tirmizi, 1964 and U. spinirostris ( Ahyong & Poore, 2004) . Their relationships are discussed under U. senarius (see below). From all of these relatives U. numerosus differs in the following particulars: the rostrum is proportionately broad distally, not triangular, with a row of 9 lateral spines along the entire length; the abdominal somite 1 bears a transverse row of 6 spines, and the somites 2-6 each bear more numerous spines; and sternite 4 bears 2 rows of spines arranged in concentric arcs.

Figures

FIGURE 176 Uroptychus numerosus n.sp.,holotype,male 4.1 mm (MNHN-IU-2014-16830).A, carapace and anterior part of abdomen,dorsal.B, same, lateral. C, sternal plastron, with excavated sternum and basal parts of Mxp1. D, telson. E, left antenna, ventral.F, right Mxp3, ventral. G, same, lateral.H, right P1, dorsal.Scale bars:1 mm.

FIGURE 177 Uroptychus numerosus n. sp.,holotype, male 4.1 mm (MNHN-IU-2014-16830). A, left P2, lateral. B, same, distal part, setae omitted,lateral.C, same, propodus, flexor. D, left P3, lateral. E, left P4, lateral. Scale bars: 1 mm.