Uroptychus clarki, 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 : 136-140

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Uroptychus clarki

n. sp.

Uroptychus clarki n. sp.

Figures 53 View FIGURE 53 , 54 View FIGURE 54

TYPE MATERIAL — Holotype: New Caledonia, Norfolk Ridge. NORFOLK 1 Stn DW 1697, 24°39’S, 168°38’E, 569-616 m, 24.VI.2001, 1 ov. ♀ 5.5 mm ( MNHN-IU-2013-8575 ). GoogleMaps

ETYMOLOGY„ Named after Paul F. Clark for his friendship and help in arranging loans of material.

DESCRIPTION„ Medium-sized species. Carapace: Broader than long (0.7 × as long as broad); greatest breadth 2.0 × distance between anterolateral spines. Dorsal surface smooth, somewhat convex from anterior to posterior, with feeble depression between gastric and cardiac regions; ridged along posterior fifth of lateral margin; epigastric region with pair of short stout spines flanked by 2 small spines placed side by side. Lateral margins concave or weakly constricted at distal third; anterior part (hepatic and anterior branchial margins) gently divergent posteriorly, with 4 spines: first anterolateral, strong, directed straight forward, reaching cornea, second and third small, situated at level of first in lateral view, directed anteriorly, fourth strong but smaller than first, directed anterolaterally; posterior part (posterior branchial margin) convex, with 5 short spines, first spine remotely separated from fourth spine on anterior part, last spine followed by ridge. Rostrum narrow triangular, with interior angle of 29°, directed slightly dorsally on dorsal surface, strongly so on ventral surface; length 0.8 × breadth, 0.3 × that of remaining carapace; dorsal surface somewhat concave; breadth much less than half carapace breadth measured at posterior carapace margin. Lateral orbital spine small, situated somewhat anterior to level of anterolateral spine. Pterygostomian flap anteriorly angular, produced to strong spine, surface with 3 spines arranged roughly in longitudinal row on anterior part; height of posterior half about 0.4 × that of anterior half.

Sternum: Excavated sternum sharply ridged in midline on surface, anterior margin produced triangularly between bases of Mxp1. Sternal plastron 1.6 × broader than long, lateral extremities convexly divergent behind sternite 4, sternite 7 slightly narrower than sternite 6. Sternite 3 shallowly depressed; anterior margin moderately concave, with V-shaped median notch, with no submedian spines. Sternite 4 short relative to breadth; anterolateral margin convex, anteriorly rounded, length 2.0 × that of posterolateral margin. Sternite 5 with convex anterolateral margin 1.3 × longer than posterolateral margin of sternite 4.

Abdomen: Somites short relative to breadth. Somite 1 well convex from anterior to posterior. Somite 2 tergite 3.4 × broader than long, pleuron well produced posterolaterally. Pleuron of somite 3 tapering to blunt terminus. Telson 0.5 × as long as broad; posterior plate 1.5 × longer than anterior plate, posterior margin distinctly emarginate.

Eye: Elongate, 2.0 × longer than broad, reaching apex of rostrum, feebly narrowed medially. Cornea slightly more than half length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 3.0 × longer than high. Antennal article 2 with strong distolateral spine. Antennal scale proportionately broad, 1.6 × broader than article 5, ending in point proximal third of length of article 5. Article 4 unarmed. Article 5 also unarmed, length 1.4 × that of article 4, breadth 0.5 × height of ultimate article of antennule. Flagellum of 15 segments not reaching distal end of P 1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with 1 obsolescent denticle on mesial ridge. Ischium having flexor margin distally rounded, crista dentata with about 20 tiny denticles. Merus twice as long as ischium, mesial face flattish; flexor margin roundly ridged on proximal half, sharply ridged on distal half, with blunt eminence distal to midlength; laterally with short blunt distal spine. Carpus unarmed.

P 1: 6.7 × longer than carapace, smooth and barely setose except for fingers. Ischium with strong dorsal spine; ventromesial margin with subterminal spine very short and blunt, not reaching distal end of ischium, proximally with obsolescent protuberances. Merus with 2 rows of short blunt spines along mesial margin (2 dorsomesial spines, 5 ventromesial spines), and a few low blunt processes or spines on ventral surface directly distal to ischium; ventral distomesial spine short and blunt; length 1.2 × that of carapace. Carpus 1.5 × length of merus, distally with dorsomesial spine. Palm unarmed, slightly broadened distally, 3.8 × longer than broad. Fingers relatively slender distally, sparingly setose, moderately gaping in proximal three-quarters, not crossing distally; fixed finger directed slightly laterally; movable finger 0.5 × as long as palm, opposable margin with prominent median process (distal margin of process perpendicular to opposable margin) on gaping margin; no longitudinal groove on ventromesial face of fixed finger.

P 2-4: Relatively slender, well compressed mesio-laterally, with sparse simple setae, numerous on dactyli. Ischia with 2 short dorsal spines. Meri successively shorter posteriorly ( P 3 merus 0.9 × length of P 2 merus, P 4 merus 0.6 × length of P 3 merus); subequally broad on P 2 and P 3, slightly narrower on P 4; dorsal margin unarmed; length-breadth ratio, 4.6 on P 2, 4.3 on P 3, 3.0 on P 4; P 2 merus 0.8 × as long as carapace, 1.1 × longer than P 2 propodus; P 3 merus subequal to length of P 3 propodus, P 4 merus 0.7 × length of P 4 propodus. Carpi successively shorter posteriorly, carpus-propodus length ratio, 0.5 on P 2, 0.4 on P 3, 0.3 and P 4. Propodi subequal in length on P 2 and P 3, shortest on P 4; flexor margin slightly concave in lateral view, with pair of slender terminal spines only. Dactyli subequal in length on P 2-4; dactylus-carpus length ratio, 1.3 on P 2, 1.6 on P 3, 2.0 on P 4; dactylus-propodus length ratio, 0.6 on P 2 and P 3, 0.7 on P 4; flexor margin slightly curving, with 9 sharp spines proximally diminishing, loosely arranged and nearly perpendicular to margin, ultimate spine shorter and more slender than penultimate, penultimate somewhat broader than antepenultimate.

Eggs. Number of eggs carried, 38; size, 0.97 × 1.12 mm - 1.08 × 1.10 mm.

REMARKS — The carapace shape including the presence of a pair of epigastric spines, the pterygostomian flap with spines on the anterior surface and the spination of P 2-4, especially the arrangement of spines on dactyli, are similar in U. clarki n. sp., U. corbariae n. sp., U. defayeae n. sp., U. mesodme n. sp., U. paraplesius n. sp. and U. trispinatus n. sp. These species also share a well depressed cephalothorax especially in the posterior half: the pterygostomian flap is posteriorly lowered, the height of posterior half 0.4-0.5 times that of anterior half. The first three species differ from the latter three species in having the carapace lateral margin with irregular spines (lacking three strong spines) on the anterior portion and in having the antennal article 4 unarmed and the antennal scale barely reaching the midlength of article 5. Characters to distinguish U. clarki from U. corbariae and U. defayeae are outlined in the accounts of the latter two species (see below).