Uroptychus senticarpus, 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 : 466-470

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Uroptychus senticarpus

n. sp.

Uroptychus senticarpus n. sp.

Figures 233 View FIGURE 233 , 234 View FIGURE 234

TYPE MATERIAL — Holotype: New Caledonia, Norfolk Ridge. NORFOLK 2 Stn DW 2072, 25°21.25’S, 168°57.16’E, 1000-1005 m, 26.X.2003, ♀ 3.7 mm ( MNHN-IU-2013-8512 ) GoogleMaps . Paratype: Collected with holotype, 1 ♂ 3.7 mm ( MNHN- IU-2013-8513) .

ETYMOLOGY„ The specific name is a noun in apposition from the Latin sentis (= thorn) plus carpus (= wrist joint), alluding to a pronounced spine on the dorsodistal margin of P 1 carpus.

DISTRIBUTION„ Norfolk Ridge, 1000-1005 m.

DESCRIPTION„ Carapace: 1.3 × broader than long (0.8 × as long as broad), broadest on posterior third; greatest breadth 1.8 × distance between anterolateral spines. Dorsal surface convex from anterior to posterior, smoothly sloping down to rostrum, thickly covered with small pits suggesting supporting fine setae. Lateral margins convex, with row of finely granulate ridges; anterolateral spine distinctly larger than lateral orbital spine, directed anterolaterally. Rostrum distally broken, horizontal, narrow triangular, with interior angle 20°; dorsal surface somewhat concave; lateral margin straight with a few very small spines distally; length presumably more than half that of remaining carapace, breadth 0.4 × that of carapace measured along posterior margin. Lateral orbital angle produced to small spine, separated from anterolateral spine by basal breadth of latter spine, and located slightly anterior to that spine. Pterygostomian flap smooth on surface, anterior margin angular, produced to small spine.

Sternum: Excavated sternum with convex anterior margin; surface with low ridge in midline. Sternal plastron 0.8 × as long as broad; lateral extremities convexly divergent posteriorly. Sternite 3 shallowly depressed; anterior margin excavated in broad V-shape, without median notch and submedian spines (with very small median notch in paratype). Sternite 4 with anterolateral margin 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 convex from anterior to posterior, without transverse ridge. Somite 2 tergite 3.1 × broader than long; pleural lateral margin concavely divergent posteriorly, posterolateral end blunt. Pleuron of somite 3 with blunt posterolateral terminus. Telson 0.5 × as long as broad; posterior plate 1.5 × longer than anterior plate, deeply concave on posterior margin.

Eye: 1.3 × longer than broad, distally narrowed, lateral and mesial margins somewhat convex; cornea two-thirds as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 4.2 × longer than high. Antennal peduncle extending far beyond eye. Article 2 with small lateral spine. Antennal scale 2.0 × broader than article 5, extending slightly beyond proximal first segment of flagellum, greatly overreaching eye. Articles 4 and 5 each with small distomesial spine, article 5 1.7 × longer than article 5, breadth 0.5 × height of antennular ultimate article. Flagellum of 7 segments slightly falling short of distal margin of P 1 merus.

Mxp: Mxp1 with bases broadly separated. Mxp3 with relatively long simple (not plumose) setae other than brushes on distal articles. Basis smooth on mesial ridge. Ischium with flexor margin not rounded distally; crista dentata with about 35 small denticles of subequal size. Merus 2.2 × longer than ischium, flexor margin roundly ridged, with 3 tiny spines on distal third. Small distodorsal spine on each of merus and carpus.

P 1: 4.7 × longer than carapace, sparingly covered with relatively short fine setae. Ischium with small triangular dorsal spine, ventromesial margin with a few denticles proximally, subterminal spine vestigial. Merus with minutely denticulate short ridges supporting setae on surface; with small distomesial and distolateral spines on ventral surface, row of denticles along distodorsal margin, and very small spines along mesial margin; length subequal to that of carapace. Carpus 1.2 × longer than merus, with a few small dorsal tubercles and a few small mesial spines on proximal portion, distodorsal margin with well-developed median spine flanked by a few denticles. Palm 4.1 × longer than broad, 1.1 × longer than carpus. Fingers moderately depressed and relatively narrow, not gaping, distally incurved, crossing when closed; fixed finger sinuous on opposable margin; movable finger half as long as palm, opposable margin with low proximal process.

P 2-4: Relatively broad and somewhat compressed mesio-laterally, with fine soft setae. Meri successively shorter posteriorly ( P 3 merus 0.9 × length of P 2 merus, P 4 merus 0.7 length of P 3 merus); breadths subequal on P 2-4; lengthbreadth ratio, 4.4 on P 2, 3.8 on P 3, 2.5 on P 4; dorsal margin rounded, not cristiform, smooth and unarmed on P 2-4. P 2 merus 0.7 × as long as carapace, 1.1 × length of P 2 propodus; P 3 merus 0.9 × 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 and P 3, 0.4 on P 4. Propodi longer on P 3 than on P 2 and P 4, subequal on P 2 and P 4; flexor margin somewhat convex on distal portion, ending in pair of terminal spines preceded by 5, 3, 2 spines on P 2, P 3, P 4 respectively at most on distal third. Dactyli successively longer posteriorly, moderately curving; flexor margin with 7, 7, 8 strong spines loosely arranged, proximally diminishing and somewhat inclined on P 2, P 3, P 4 respectively; dactylus-carpus length ratio, 0.8, 0.9, 1.2 on P 2, P 3, P 4 respectively.

REMARKS„ The anterior margin of sternite 3 is somewhat different between the available two type specimens: a broad V-shape in the holotype, additional very small median notch in the paratype. Uroptychus senticarpus n. sp., U. plumella n. sp. and U. shanei n. sp. belong to a group of species characterized by the carapace lateral margin bearing an anterolateral spine only, sternite 3 with the anterior margin emarginate in a broad V-shape, P 1 nearly spineless, with fingers distally strongly incurved, and the P 2-4 dactyli ending in a strong spine preceded by similar, proximally diminishing spines.

Uroptychus senticarpus is distinguished from U. plumella by the anterolateral spine of the carapace that is directed anterolaterally instead of straight forward; the antennal article 2 is produced to a small spine instead of being acuminate without a distinct spine, and the articles 4 and 5 each bearing a distinct spine instead of a tiny one (that of article 4 tuberclelike); the Mxp3 crista dentata bears numerous minute denticles instead of loosely arranged, distally diminishing denticles; and the pterygostomian flap is produced to a sharp spine instead of bearing small spine. Distinguishing characters between U. senticarpus and U. shanei are discussed under the accounts of the latter species (see below).