Uroptychus lanatus, 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 : 256-259

Uroptychus lanatus n. sp.

Figures 117 , 118

TYPE MATERIAL — Holotype: Indonesia, Kai Islands. KARUBAR Stn CP17, 5°15’S, 133°01’E, 459- 439 m, with coral, possibly belonging to Chrysogorgiidae ( Calcaxonia) , 24.X.1991, ov. ♀ 2.8 mm ( MNHN-IU-2011-5958 ) . Paratypes: Collected with holotype, same host, 3 ♂ 2.4-3.0 mm, 2 ov. ♀ 2.7, 3.0 mm (MNHN-IU-2011-5960, MNHN-IU-2011-5961, MNHN-IU-2014-16611) . Vanuatu. MUSORSTOM 8 Stn CP975, 19°23.60’S, 169°28.93’E, 566- 536 m, 22.IX.1994, 1 ♀ 3.8 mm (MNHN-IU-2011-5959).

ETYMOLOGY„ From the Latin lanatus (soft), alluding to soft setae covering the body, characteristic of the species.

DISTRIBUTION„ Kai Islands and Vanuatu; 459- 536 m.

SIZE„ Males, 2.4-3.0 mm; females 2.7-3.8 mm; ovigerous females from 2.7 mm.

DESCRIPTION„ Small species. Body densely covered with soft fine setae. Carapace: 1.1-1.2 × broader than long; greatest breadth 1.7 × distance between anterolateral spines. Dorsal surface somewhat convex from anterior to posterior, without distinct groove. Lateral margins convexly divergent posteriorly, bearing several small spines; first anterolateral, largest, slightly overreaching lateral orbital spine; second rather remote from first, usually equidistant between first and third, rarely with accompanying small spine mesial to it; remaining spines situated on anterior half of posterior branchial region. Rostrum sharply triangular, with interior angle of 25-27°, deflected ventrally; length about half or slightly less than half that of remaining carapace, breadth distinctly less than half carapace breadth at posterior carapace margin; dorsal surface concave. Lateral orbital spine smaller than, moderately remote from, and slightly anterior to level of anterolateral spine. Pterygostomian flap anteriorly angular, produced to small spine, surface unarmed.

Sternum: Excavated sternum anteriorly triangular, surface with weak ridge in midline. Sternal plastron much broader than long, lateral extremities convexly divergent posteriorly. Sternite 3 weakly depressed; anterior margin nearly semicircular or of very broad V-shape, without median notch and submedian spines, laterally sharply produced or bluntly angular. Sternite 4 having anterolateral margin convex, anteriorly rounded, bearing a few distinct or obsolescent denticles, posterolateral margin short, less than half as long as anterolateral margin. Anterolateral margin of sternite 5 strongly convex, much longer than (2 x) posterolateral margin of sternite 4.

Abdomen: Somite 1 slightly convex from anterior to posterior, without transverse ridge. Somite 2 tergite 2.4-2.9 × broader than long; pleuron posterolaterally blunt, lateral margin slightly concave, moderately divergent posteriorly. Pleuron of somite 3 with blunt lateral margin. Telson 0.4 × as long as broad; posterior plate nearly as long as or slightly shorter than anterior plate, posterior margin feebly or somewhat concave, not emarginate.

Eye: Relatively short (1.4-1.6 × longer than broad), terminating in midlength of rostrum, medially somewhat inflated, distally narrowed. Cornea not dilated, about half length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 2.8-3.0 × longer than high. Antennal peduncle overreaching eyes by half length of article 5. Article 2 with small lateral spine. Antennal scale distinctly overreaching distal end of antennal peduncle, breadth 1.7 × that of article 5 or slightly more. Articles 4 and 5 each with distoventral spine very small or barely discernible. Article 5 1.3-1.5 × length of article 4, breadth 0.6-0.7 height of ultimate article of antennular peduncle. Flagellum of 10-11 segments reaching or somewhat overreaching distal end of P1 merus.

Mxp: Mxp1 with bases close to each other but not contiguous. Mxp3 with plumose setae on lateral surface of merus and carpus, other than brushes. Basis without denticles on mesial ridge. Ischium with flexor margin not rounded distally; crista dentata with numerous small distally diminishing denticles. Merus 2.1 × as long as ischium, flattish on mesial face, with distinct distolateral spine and a few small or obsolescent spines anterior to midlength of flexor margin. Carpus with small or obsolescent distolateral spine.

Pereopods thickly covered with soft, fine, plumose setae. P1: Massive, 4.7-4.8 × (males), 3.9-4.1 × (females) longer than carapace. Ischium dorsally with short spine, ventromesially with several small spines obscured by setae, subterminal spine very small. Merus 0.8-1.0 × length of carapace, usually with ventral distomesial spine, rarely with a few tubercular processes on proximal mesial margin. Carpus 1.1 × longer than merus. Palm 2.5-2.7 × (females), 2.5-3.0 × (males) longer than broad, 1.2-1.6 × longer than carpus. Fingers depressed, relatively broad, directed straight forward in females and small males, somewhat laterally directed in largest male, distally incurved, crossing when closed; movable finger having opposable margin with bluntly triangular median process fitting to groove between 2 low eminences on opposite face of fixed finger when closed, length usually 0.4 ×, rarely 0.5 × (non-ovigerous female) that of palm.

P2-4: Somewhat compressed mesio-laterally. Meri and carpi unarmed. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus, P4 merus 0.8 × length of P3 merus), subequally broad on P2 and P3, very slightly narrower on P4 than on P3; length-breadth ratio, 3.2-3.9 on P2, 3.1-3.9 on P3, 2.6-3.2 on P4; dorsal margin unarmed; P2 merus 0.7-0.8 length of carapace, 0.9 × length of P2 propodus; P3 merus 0.9 × length of P3 propodus; P4 merus 0.7-0.8 × length of P4 propodus. Carpi subequal in length on P2 and P3 or slightly longer on P2 than on P3 and shortest on P4; carpus-propodus length ratio, 0.5 on P2, 0.4-0.5 on P3, 0.4 on P4; unarmed. Propodi subequal on P2-4 or longer on P3-4 than on P2; flexor margin slightly convex (rarely somewhat more convex on P2), ending in pair of spines preceded by 6-7 slender movable spines on distal two-thirds on P2, 6 spines in distal half on P3, 4-5 spines on P4. Dactyli longer on P3 and P4 than on P2; dactylus-carpus length ratio, 0.9-1.0 on P2, 1.0-1.1 on P3, 1.2 on P4; dactylus-propodus length ratio, 0.4-0.5 on P2-4; flexor margin moderately curving, ending in slender spine preceded by 7-9 subtriangular, moderately obliquely directed spines diminishing toward juncture with propodus, ultimate somewhat more slender than penultimate.

Eggs. Number of eggs carried, 10; size, 0.83 mm × 0.83 mm - 1.0 mm × 1.25 mm (smallest eggs yolky).

REMARKS — Uroptychus lanatus keys out together with U. perpendicularis n. sp., but it is closer to U. posticus n. sp. Their relationships are discussed under the remarks of that species (see below).

Figures

FIGURE 117 Uroptychus lanatusn.sp.,holotype,ovigerous female 2.8 mm (MNHN-IU-2011-5958).A, carapace and anterior part of abdomen,proximal part of left P1 included, setae omitted from abdomen,dorsal. B, same,setae omitted, lateral.C, anterior part of sternal plastron, with excavated sternum and basal parts of Mxp1.D, telson.E, left antenna,ventral.F, left Mxp3,ventral.G, same,merus and carpus,lateral.H, left P1,proximal part,setae omitted,ventral.I, same,setae omitted from carpus,dorsal. Scale bars:1 mm.

FIGURE 118 Uroptychus lanatus n. sp., holotype, ovigerous female 2.8 mm (MNHN-IU-2011-5958). A, right P2, lateral. B, same, distal part, setae omitted, lateral. C, right P3,setae omitted, lateral. D, right P4, setae omitted,lateral. Scale bars:1 mm.