Uroptychus adnatus, 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 : 45-48

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Uroptychus adnatus

n. sp.

Uroptychus adnatus n. sp.

Figures 7 View FIGURE 7 , 8 View FIGURE 8

TYPE MATERIAL — Holotype: Vanuatu. MUSORSTOM 8 Stn CP 1111, 14°51.09’S, 167°14.00’E, 1210-1250 m, 8.X.1994,

1 ♂ 8.9 mm ( MNHN-IU-2014-17159 ).


ETYMOLOGY„ From the Latin adnatus (joined to, united with), alluding to the antennal scale being fused with the antennal article 2, a character displayed by the new species.

DISTRIBUTION„ Vanuatu, 1210-1250 m.

DESCRIPTION„ Carapace: Slightly longer than broad (length 1.1 × breadth); greatest breadth 1.5 × distance between anterolateral spines. Dorsal surface glabrous, with pair of strong epigastric spines and very small tubercles scattered as illustrated; distinct depression between moderately inflated gastric and cardiac regions, boundaries between cardiac and branchial regions indistinct. Lateral margins somewhat divergent posteriorly; anterolateral spine well developed, distinctly overreaching small lateral orbital spine, followed by somewhat smaller spine located at anterior end of branchial region, and some posteriorly diminishing tubercular processes on posterior branchial region; ridged along posterior third of length. Rostrum narrow, with interior angle of 20°, nearly straight, directed slightly dorsally; dorsal surface flattish, smooth and glabrous; length 0.4 × that of remaining carapace, breadth less than half carapace breadth measured at posterior carapace margin. Lateral orbital spine moderately remote from and anterior to level of anterolateral spine. Pterygostomian flap smooth on surface, anterior margin roundish, without distinct spine.

Sternum: Excavated sternum anteriorly sharp triangular, surface somewhat inflated, with no ridge in midline and no spine in center. Sternal plastron about as long as broad, lateral extremities slightly divergent posteriorly. Sternite 3 moderately depressed, anterior margin of broad V-shape with 2 very small submedian spines separated by broad sinus. Sternite 4 with denticulate transverse ridge preceded by depression (in ventral view), anterolateral margin relatively short, about quarter of greatest breadth, nearly straight, with several small tubercles, posterolateral margin relatively long, nearly as long as anterolateral margin. Sternite 5 anterolateral margin somewhat convex and much shorter than posterolateral margin of sternite 4.

Abdomen: Glabrous. Somite 1 with rounded transverse ridge. Somite 2 tergite 2.7x broader than long; pleuron with posteriorly somewhat divergent lateral margin rounded on anterior and posterior corners. Pleuron of somite 3 posterolaterally blunt. Telson slightly more than half as long as broad; posterior plate 2.3 × length of anterior plate, posterior margin emarginate.

Eye: Short relative to breath (1.4 × longer than broad), distally broadened, proximally narrowed, reaching anterior third of rostrum. Cornea slightly inflated, longer than remaining eyestalk.

Antennule and antenna: Ultimate article of antennule 3.2 × longer than high. Antennal peduncle not reaching rostral tip. Article 2 fused with antennal scale. Antennal scale short, laterally with small spine near base (somewhat distal to ordinary end of article 2), slightly overreaching distal end of article 4 but falling far short of midlength of article 5, 1.7 × broader than article 5. Article 5 2.8 × longer than article 4, breadth slightly less than half height of antennular ultimate article. Flagellum consisting of 19-21 segments.

Mxp: Mxp1 with bases close to each other, but not contiguous. Mxp3 relatively thick and not compressed mesiolaterally. Basis with 4-5 denticles on mesial ridge, distalmost larger than remainder. Ischium distally not rounded on flexor margin, crista dentata with 16 denticles. No spine on merus and carpus. Merus slightly more than 3 × longer than ischium, not crested but rounded along flexor margin.

P 1: Missing.

P 2-4: Slender, sparsely setose, moderately depressed. Meri successively shorter posteriorly ( P 3 merus 0.8 × length of P 2 merus, P 4 merus 0.9 × length of P 3 merus), subequally broad on P 2-4. Meri with small spine at distal end of flexor margin, and another small spine at distal end of extensor margin on P 2 and P 3, absent on P 4; length-breadth ratio, 7.0 on P 2, 6.1 on P 3, 5.3 on P 4; P 2 merus as long as carapace, 1.4 × longer than P 2 propodus; P 3 merus 1.2 × length of P 3 propodus; P 4 merus about as long as P 4 propodus. Carpi successively shorter posteriorly ( P 3 carpus 0.9 × length of P 2 carpus; P 4 carpus 0.9 × length of P 3 carpus), relatively long; carpus-propodus length ratio, 0.9 on P 2, 0.8-0.9 on P 3, 0.7 on P 4. Propodi subequal in length on P 2 and P 3, slightly longer on P 4; flexor margin straight, with 8 or 9 spines on P 2, 7-8 on P 3, 6 on P 4, at most on distal two-thirds, distalmost single, equidistant between juncture with dactylus and distal second spine. Dactyli subequal in length on P 2-4; dactylus-carpus length ratio, 0.5 on P 2 and P 3, 0.6 on P 4; dactylus-propodus length ratio, 0.4 × on P 2-4; strongly curved at proximal third; flexor margin with somewhat inclined short spines in 2 groups remotely separated by sharp crest, distal group of 2 spines (ultimate stronger) and proximal group of 4-5 spines.

REMARKS — This species is very similar in nearly all details to U. jiaolongae Dong & Li, 2015 from the South China Sea southwest of Taiwan. They differ only in the antennal scale, which is fused with article 2 in U. adnatus , but articulated in U. jiaolongae . The same difference also discriminates between U. scandens Benedict, 1902 and U. articulatus n. sp., its validity being supported by molecular evidence (see below under U. scandens ). Uroptychus adnatus and U. jiaolongae were taken at depths of more than 1000 m, but from disjunct localities, and the latter was found in a cold seep community. Although molecular data are not available, I believe U. adnatus can be regarded as a distinct species.

Uroptychus adnatus and U. remotispinatus Baba & Tirmizi, 1979 share the short antennal scale, sternite 4 with no strong lateral spine, relatively long P 2-4 carpi, and the P 2 dactylus with remotely separated proximal and distal groups of spines. Uroptychus adnatus differs from U. remotispinatus in having a pair of epigastric spines, in having the branchial lateral margin with a distinct spine instead of being unarmed on the anterior end, in having the P 2-4 propodi with the distalmost of the flexor marginal spines close to instead of considerably remote from the juncture with the dactylus, and the antennal scale fused with article 2.