Uroptychus palmaris, 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 : 372-375

Uroptychus palmaris n. sp.

Figures 183 , 184

TYPE MATERIAL — Holotype: New Caledonia, Norfolk Ridge. NORFOLK 1 Stn CP 1669, 23°41’S, 168°01’E, 302-325 m, 21.VI.2001, ov. ♀ 2.2 mm ( MNHN-IU-2011-5975 ) . Paratypes: New Caledonia, Norfolk Ridge. CHALCAL 2 Stn CH 03, 24°48’S, 168°09’E, 257 m, 27.X.1986, with antipatharian coral (Hexacorallia), 2 ♂ 1.7, 2.0 mm, 2 ov. ♀ 2.0, 2.3 mm (MNHN-IU-2014-16834) . – Stn CH 04, 24°44’S, 168°10’E, 253 m, 27.X.1986, antipatharian coral (Hexacorallia), 3 ♂ 1.7-1.8 mm (MNHN-IU-2011-5977, MNHN-IU-2014-16835), 1 ov. ♀ 2.1 mm (MNHN-IU-2011-5976) . – Stn DW70, 24°46.0’S, 168°09.0’E, 232 m, 27.X.1986, 1 ♂ 1.7 mm (MNHN-IU-2014-16836).

ETYMOLOGY„ From the Latin palmaris (pertaining to the palm of the hand) for the P1 palm of the species which is massive and large relative to the carapace.

DISTRIBUTION„ Norfolk Ridge; 232- 325 m.

SIZE„ Males, 1.7-2.0 mm; females, 2.0- 2.3 mm; ovigerous females from 2.0 mm.

DESCRIPTION — Small species. Carapace: 1.1-1.2 × broader than long (0.8-0.9 × as long as broad); greatest breadth 1.8 × distance between anterolateral spines. Dorsal surface smooth, sparsely setose, feebly convex from anterior to posterior, without distinct groove. Lateral margins convexly divergent posteriorly, bearing 6 spines; first anterolateral, well developed, directed anterolaterally, overreaching much smaller lateral orbital spine; second small, ventral in position, third to sixth located on branchial region, fourth more remote from third than from fifth, sixth (last) situated about at midlength of posterior branchial margin. Rostrum narrow triangular, with interior angle of 20-23°, somewhat deflected ventrally; dorsal surface concave; lateral margin with a few (usually 2) small spines near apex; length 0.6-0.7 × that of remaining carapace, breadth half carapace breadth at posterior carapace margin. Lateral orbital spine closely mesial to anterolateral spine. Pterygostomian flap anteriorly angular, produced to acute spine, surface smooth and unarmed.

Sternum: Excavated sternum smooth, without spine and ridge on surface, anterior margin broad triangular. Sternal plastron 1.3-1.4 × broader than long, broadened posteriorly. Sternite 3 shallowly depressed; anterior margin shallowly excavated, with 2 very small median spines contiguous at base, lacking median notch between, lateral limits sharply angular. Sternite 4 having anterolateral margin short relative to breadth, anteriorly with 1 or 2 small spines placed side by side, posterolateral margin half length of anterolateral margin. Anterolateral margin of sternite 5 anteriorly rounded, much longer than posterolateral margin of sternite 4.

Abdomen: Smooth and sparsely setose. Somite 1 without transverse ridge. Somite 2 tergite 2.4-2.7 × broader than long; lateral margin moderately concave and divergent posteriorly, posterolaterally blunt. Pleuron of somite 3 laterally rounded. Telson about half as long as broad; posterior plate slightly longer to slightly shorter than anterior plate, posterior margin nearly transverse, slightly concave or slightly convex.

Eye: 2 × longer than broad, overreaching midlength of, barely reaching distal third point of rostrum, slightly narrowed distally. Cornea not dilated, about half as long as remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 3.0-3.4 × longer than high. Antennal peduncle overreaching cornea but never reaching rostral tip. Article 2 with very small, occasionally obsolescent lateral spine. Antennal scale 1.8 × broader than article 5, varying from barely reaching to somewhat overreaching distal end of article 5. Articles 4 and 5 subequal in length or article 5 slightly longer, each with distinct distomesial spine; breadth of article 5 two-thirds height of ultimate antennular article. Flagellum of 10-11 segments barely reaching distal end of P1 merus.

Mxp: Mxp1 with bases close to each other. Mxp3 sparsely setose except for distal 2 articles. Basis without denticles on mesial ridge. Ischium with more than 18 distally diminishing denticles on crista dentata, flexor margin not rounded distally. Merus about twice as long as ischium, with well-developed distolateral spine and 1 or 2 small spines distal to point two-thirds of cristate flexor margin; mesial face flattish. Carpus with distinct distolateral spine.

P1: Sparsely with fine setae, 5.2-7.1 × longer than carapace, massive on palm, greatest breadth often more than distance between anterolateral spines of carapace. Ischium with sharp, strong dorsal spine, ventromesial margin with small subterminal spine proximally followed by 4 or 5 spinules. Merus 1.1 × length of carapace, bearing a few to several spines on each of mesial and ventromesial margins and dorsal surface, distomesial and mid-mesial spines well developed. Carpus 1.0-1.2 × longer than merus, distally broadened, terminally with 4 or 5 spines (2 or 3 dorsal, 1 mesial, 1 ventromesial; mesial one stronger), dorsomesially with a few to several small, often well-developed spines, dorsally 3 tubercle-like spines on proximal portion. Palm massive, 2.4-2.8 × longer than broad, smooth, without spines; length 1.0-1.3 × that of carpus. Fingers broad relative to length, distally incurved, crossing when closed; movable finger not reaching tip of fixed finger, opposable margin with low, blunt median process; length 0.4-0.6 × that of palm; fixed finger having opposable margin with prominence distal to position of opposite process of movable finger.

P2-4: Relatively short, moderately depressed, sparsely setose. Meri unarmed but dorsal margin with a few weak eminences supporting long setae on P2; length-breadth ratio, 3.3-3.5 on P2, 3.1-3.5 on P3, 2.5-2.8 on P4; breadths subequal on P2-4; P2 merus three-quarters length of carapace, as long as P2 propodus. P3 merus subequal to, rarely slightly shorter than P2 merus, 0.9 × length of P3 propodus; P4 merus 0.8 × length of P3 merus, 0.7-0.8 × length of P4 propodus. Carpi subequal in length on P2 and P3 or slightly shorter on P3 than on P2, shortest on P4 (P4 carpus 0.9 × length of P3 carpus), slightly less than half as long as propodi (carpus-propodus length ratio, 0.40-0.44, 0.36-0.44, 0.34- 0.42 on P2, P3, P4 respectively). Propodi shortest on P2, longer on P4 than on P3; flexor margin nearly straight, ending in pair of movable spines preceded by 4 or 5 similar spines in distal two-thirds of length on P2 and P3, 1 or 2 spines in distal third on P4. Dactyli proportionately broad, longer than carpi (dactylus-carpus length ratio, 1.2-1.3 on P2, 1.4-1.5 on P3 and P4), dactylus-propodus length ratio, 0.5-0.6 on P2 and P3, 0.6 on P4; flexor margin nearly straight, ending in slender terminal spine preceded by 9 or 10 well-developed triangular spines perpendicular to margin and successively diminishing toward base of article.

Eggs. Number of eggs carried 2-5; size, 0.92 mm × 0.88 mm - 1.10 mm × 1.25 mm.

REMARKS — As suggested by the species name, the P1 palm of the species is pronouncedly broad, often more than the distance between the anterolateral spines of the carapace.

Uroptychus palmaris somewhat resembles U. yaldwyni Schnabel, 2009 from the Kermadec Ridge, in having the anterolateral spine that is close to the smaller lateral orbital spine, the elongate eyes, an antennal article 5 that is slightly longer than article 4, and the P2-4 dactyli that are longer than the carpi, with the ultimate spine much more slender than the penultimate spine. However, the new species is distinguished from that species by the following: the last carapace lateral spine is located at the midpoint instead of near the posterior end of the branchial margin; the anterior margin of sternite 3 is weakly instead of strongly excavated, with 2 very small median spines closely placed side by site instead of acute submedian spines separated by a distinct notch; the anterolateral margin of sternite 4 is twice instead of subequal to the length of the posterolateral margin, and the surface of the pterygostomian flap is more sharply angular, the surface being smooth instead of covered with small spines.

Uroptychus palmaris also resembles U. triangularis Miyake & Baba, 1967 in having two small, closely placed median spines on the concave anterior margin of sternite 3, but it differs from that species in having the branchial marginal spines rather small instead of short but broad at base, in having the P2-4 meri unarmed instead of bearing a row of dorsal spines. At first glance, the carapace in U. palmaris is not so strongly broadened posteriorly as in U. triangularis (the greatest breadth is 1.8 versus 2.2 times the distance between left and right anterolateral spines).

Figures

FIGURE 183 Uroptychus palmaris n. sp., holotype, ovigerous female 2.2 mm (MNHN-IU-2011-5975). A, carapace and anterior part of abdomen, proximal part of left P1 included,dorsal.B, same,lateral.C, sternal plastron,with excavated sternum and basal parts of Mxp1.D, telson.E, right antenna, ventral.F, right Mxp3, setae omitted, ventral.G, same,setae omitted,lateral. Scale bars:1 mm.

FIGURE 184 Uroptychus palmaris n.sp.,holotype,ovigerous female 2.2 mm (MNHN-IU-2011-5975).A, left P1,proximal part,setae omitted,ventral.B,same, proximal part omitted,dorsal.C, right P2, lateral. D, same,distal part,setae omitted, lateral.E, right P3, setae omitted,lateral.F, same, distal part, setae omitted,lateral.G, right P4, setae omitted,lateral.H, same,distal part, setae omitted, lateral. Scale bars: 1 mm.