Uroptychus echinatus, 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 : 193-196

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Uroptychus echinatus

n. sp.

Uroptychus echinatus n. sp.

Figures 84 View FIGURE 84 , 85 View FIGURE 85

TYPE MATERIAL — Holotype: New Caledonia, Hunter and Matthew Islands . VOLSMAR Stn DW 05, 22°26’S, 171°46’E, 620-700 m, 01.VI.1989, ov. ♀ 4.9 mm ( MNHN-IU-2014-16438 ) GoogleMaps . Paratypes: Collected with the holotype, 1 ♂ 3.2 mm, 1 ♀ 3.5 mm (MNHN-IU-2014-16439).

ETYMOLOGY„ From the Latin echinatus (spiny), alluding to the spiny propodi of the walking legs.

DISTRIBUTION„ Hunter and Matthew Islands; 700 m.

DESCRIPTION„ Small species. Carapace: Slightly shorter than broad; greatest breadth 1.6 × distance between anterolateral spines. Dorsal surface convex from anterior to posterior, thickly or moderately setose, with a few scattered small spines on hepatic and lateral epigastric regions. Lateral margins convex, ridged along posterior fourth of length, bearing about 6 small spines: first anterolateral, slightly overreaching much smaller lateral orbital spine, well separated from and slightly posterior to level of that spine, followed by a few very tiny spines along hepatic margin and 5 distinct spines along branchial margin. Rostrum with interior angle of ca. 25°, nearly straight horizontal; length about half that of remaining carapace, breadth about half carapace breadth measured at posterior carapace margin; lateral margin somewhat concave, with 1 or 2 small spines near tip; dorsal surface concave and setose. Pterygostomian flap moderately setose, with tiny or obsolescent spines on anterior surface; anterior margin angular, produced to small spine.

Sternum: Excavated sternum broadly convex on anterior margin, with ridge in midline on anterior half surface. Sternal plastron as long as broad, gradually broadened posteriorly. Sternite 3 strongly depressed; anterior margin moderately excavated with small or relatively broad median notch without (holotype) or with (paratypes) small flanking spine, lateral terminus sharp angular. Sternite 4 with relatively short, nearly straight anterolateral margin ending anteriorly in strong or medium-sized spine with accompanying smaller spine lateral or mesial to it; surface with short striae supporting long setae; posterolateral margin slightly shorter than anterolateral margin. Anterolateral margins of sternite 5 subparallel, anteriorly rounded and tuberculose, about as long as posterolateral margin of sternite 4

Abdomen: Less setose than carapace. Somite 1 gently convex from anterior to posterior, with thick setae in transverse line. Somite 2 tergite 2.6-2.7 × broader than long; pleural lateral margin moderately concavely divergent, posterolaterally blunt. Pleuron of somite 3 laterally blunt. Telson half as long as broad; posterior plate concave on posterior margin, length 1.2-1.4 × that of anterior plate.

Eye: 1.6-1.7 × longer than broad, slightly overreaching midlength of rostrum, dorsally bearing setae proximal to cornea, somewhat broadened proximally. Cornea not dilated, more than half as long as remaining eyestalk.

Antennule and antenna: Antennular ultimate article 3.0-3.5 × longer than high. Antennal peduncle extending far beyond cornea, reaching subapical spine of rostrum. Article 2 with acute lateral spine. Antennal scale more than 1.5 × broader than article 5, overreaching distal end of article 5 by two proximal segments of flagellum. Distal 2 articles each with acute distomesial spine. Article 5 1.5 × longer than article 4, breadth three-fifths to three-quarters height of antennular ultimate article. Flagellum consisting of 8-10 segments, reaching distal end of P 1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 with relatively long, sparse setae other than mesial brushes. Basis with 1 or 2 obsolescent denticles on mesial ridge. Ischium with very small or obsolescent denticles on crista dentata, flexor margin distally rounded. Merus relatively short, 1.5 × longer than ischium, flattened, with well-developed distolateral spine and 2 or 3 spines distal to midlength of flexor margin. Carpus with 1 distinct distolateral and 1 small midlateral spine.

P 1: 4.0-4.3 × longer than carapace, with thick simple long setae arising from scale-like granulate ridges. Ischium dorsally with strong spine, ventromesially with strong sharp subterminal spine proximally followed by successively diminishing small spines. Merus subequal to carapace in length, bearing rows of both ventral and mesial spines; terminal margin (at junction with carpus) with a few small dorsal spines and well-developed mesial and lateral spines on ventral and dorsal sides. Carpus 1.2 × longer than merus, dorsally with 3 rows of spines. Palm unarmed, 2.9-3.2 × longer than broad, 0.9- 1.0 × length of carpus. Fingers not gaping, distally incurved, crossing when closed; opposable margins finely denticulate, that of movable finger with low prominence (on proximal third) fitting to opposing longitudinal narrow groove on fixed finger when closed; movable finger slightly more than half length of palm.

P 2-4: Relatively short, with granulate scale-like ridges supporting coarse setae. Meri equally broad on P 2-4, moderately compressed mesio-laterally, very setose like P 1; P 3 merus subequal to or slightly shorter than P 2 merus; P 4 merus 0.9 length of P 3 merus; dorsal margins with row of small spines; ventrolateral margins distally ending in distinct spine proximally followed by granulate eminences; length-breadth ratio, 3.8-3.9 on P 2, 3.6-3.8 on P 3, 3.1-3.2 on P 4; P 2 merus 0.8 × length of carapace, 0.9-1.0 × length of P 2 propodus; P 3 merus 0.8 × length of P 3 propodus; P 4 merus 0.7-0.8 × length of P 4 propodus. P 3 carpus 0.92-0.96 × length of P 2 carpus; P 4 carpus 0.91-0.95 × length of P 3 carpus; extensor margin with row of spines paralleling another row of smaller spines on dorsolateral surface; carpus-propodus length ratio about 0.4 on P 2-4. Propodi slightly longer on P 2 and P 4 than on P 3 or subequal on P 3 and P 4 and shorter on P 2; extensor margin with row of 5-6 acute immovable spines, unarmed on distal third; flexor margin ending in pair of movable spines preceded by 1 or 2 similar spines. Dactyli subequal, proportionately broad; dactylus-carpus length ratio, 1.2 on P 2, 1.3 on P 3, 1.4 on P 4, dactylus-propodus length ratio, 0.5-0.6 on P 2 and P 3, 0.5 on P 4; flexor margin straight, with 13 spines on P 2, 14 or 15 on P 3 and P 4, all not contiguous to one another and obliquely directed, ultimate slender, penultimate more than 2 × broader than antepenultimate, remaining spines slender, antepenultimate somewhat narrower than ultimate.

Eggs. Eggs carried 3 in number; size, 1.10 mm × 1.30 mm.

REMARKS — The new species resembles U. multispinosus Ahyong & Poore, 2004 (see below) in having small spines along the carapace lateral margin, the trifid apex of the rostrum, the antenna bearing a strong distomesial spine on each of articles 4 and 5 and the antennal scale overreaching article 5. However, U. echinatus is readily distinguished from that species by the following differences: the P 1 ischium bears a strong subterminal spine instead of being unarmed on the ventromesial margin; the flexor margins of P 2-4 dactyli bear strongly inclined, slender spines proximal to the pronounced penultimate spine, instead of proximally diminishing, somewhat inclined, subtriangular spines; and the extensor margins of carpi and propodi bear a row of spines instead of being smooth and unarmed. In addition, the carapace is thickly setose, instead of sparsely so.

The combination of the following characters links the species to U. alophus n. sp., U. karubar n. sp., U. longior Baba, 2005 , U. nanophyes McArdle, 1901 and U. tracey Ahyong, Schnabel & Baba, 2015 : the P 2-4 dactyli having the flexor margin with more than 10 closely arranged spines proximal to the pronounced penultimate spine, the P 2-4 carpi with a few to several extensor marginal spines, and the carapace lateral margin with at least six spines. Uroptychus nanophyes is readily distinguished from all the others by having a row of ventrolateral spines on the P 2-4 meri and by the antennal scale not overreaching the antennal article 5. Uroptychus echinatus differs from the rest of the species in having a very setose carapace with small lateral spines.