Uroptychus quartanus, 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: 435-438
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Uroptychus quartanus n. sp.
ETYMOLOGY„ From the Latin quartanus (of the fourth), referring to the fourth thoracic sternite that is much broader than the other sternites in the new species.
DISTRIBUTION„ Kai Islands; 315- 349 m.
DESCRIPTION„ Body and appendages very spinose, sparsely with relatively short setae.
Carapace: 0.9 × as long as broad; greatest breadth 1.3 × distance between anterolateral spines. Dorsal surface moderately convex from anterior to posterior, posterior cervical groove distinct, cardiac region well circumscribed. Strong spines as described below and scattered small spines: 3 equally strong spines in midline, first spine directly behind rostrum, flanked by smaller spine; second spine located at posterior gastric region, flanked by slightly anteriorly located strong spine; third spine on posterior part of cardiac region, flanked by equally strong spine situated on posterior branchial region. Lateral margins convexly divergent posteriorly with weak constrictions at anterior third (between anterior and posterior branchial regions), with 3 spines along hepatic region and 5 strong spines along branchial region; anterolateral spine well developed, directed anterolaterally, slightly overreaching lateral orbital spine; second and third small, ventral to level of remainder, last spine near posterior end. Rostrum directed somewhat dorsally, narrow triangular, with interior angle of 20°, laterally with 1 (left) or 2 (right) anterodorsally directed submedian spines; length half that of remaining carapace, breadth somewhat more than half carapace breadth at posterior carapace margin. Lateral orbital spine small, situated directly lateral to and rather remote from anterolateral spine. Pterygostomian flap anteriorly roundish, ending in sharp spine, surface covered with small spines.
Sternum: Excavated sternum with subtriangular anterior margin, anterior surface sharply cristate in midline. Sternal plastron slightly broader than long, broadest on sternite 4, lateral extremities subparallel between sternites 5-7. Sternite 3 having anterior margin strongly excavated, representing V-shape, with 2 submedian spines separated by narrow notch; anterolaterally angular, ending in 2 small spines. Sternite 4 with 2 strong spines on anterolateral margin, posterior stronger; surface with denticle-like very small spines arranged in concentric arc and fine setae; posterolateral margin about as long as anterolateral margin. Sternite 5 with anterolateral spine, anterolateral margins subparallel, shorter than posterolateral margin of sternite 4.
Abdomen: With sparse setae and sharp spines. Somite 1 with 3 (1 median and 2 lateral) spines. Somite 2 tergite 2.4 × broader than long; with anterior row of 4 well-developed spines and 2 posterior spines each placed laterally; pleuron anterolaterally angular, posterolaterally produced and tapering to sharp point; lateral margin strongly concave. Somite 3 with anterior row of 6 large spines followed by 2 small submedian spines; pleuron tapering to sharp point. Somite 4 with
anterior row of 6 spines, with no posterior spines. Somite 5 with 2 anterior spines. Somite 6 unarmed. Telson 0.65 × as long as broad; posterior plate 1.7 × longer than anterior plate, subsemicircular. Uropodal protopod with small protuberance on posterior margin near endopod; endopod 1.8 × longer than broad.
Eye: 2 × longer than broad, distally narrowed, somewhat constricted proximal to cornea, slightly overreaching midlength of rostrum. Cornea half as long as remaining eyestalk.
Antennule and antenna: Ultimate article of antennule 2.7 × longer than high. Antennal peduncle reaching rostral tip. Article 2 with sharp distolateral spine. Antennal scale narrower than peduncle, reaching distal end of article 5. Article 3 with small distomesial spine. Article 4 with ventral distomesial spine. Article 5 1.7 × longer than article 4, with 1 distodorsal and 3 ventral spines (distoventral largest); breadth 0.6 × height of antennular ultimate article. Flagellum of 9 segments falling short of distal end of P 1 merus.
Mxp: Mxp1 with bases broadly separated. Mxp3 with strong distolateral spine on coxa, ischium, merus and carpus. Basis with a few obsolescent denticles on mesial ridge. Ischium with flexor margin not rounded distally, crista dentata with 5-6 denticles irregularly distant from one another. Merus 2.1 × longer than ischium, with 1 distolateral, 3 flexor marginal spines. Carpus with 1 strong distolateral and 2 smaller extensor marginal spines.
P 1: 7.7 × longer than carapace, moderately setose. Spines in 8 rows on merus, carpus, propodus: 2 dorsal, 2 mesial (dorsal and ventral), 2 lateral (dorsal and ventral), and 2 ventral. Ischium with strong ventromesial subterminal spine and strong distodorsal spine, other than small spines. Merus 1.5 × longer than carapace. Carpus 1.7 × length of merus. Palm 4.8 × longer than broad, subequal to carpus. Fingers broad relative to length, slightly incurved distally, somewhat gaping; movable finger with small spine at proximal quarter of mesial margin, opposable margin with 2 submedian processes; fixed finger with low process or prominence opposing to proximal process of movable finger.
P 2-4: Moderately setose. Meri successively shorter posteriorly ( P 3 merus 0.9 × length of P 2 merus, P 4 merus 0.9 × length of P 3 merus), equally broad on P 2-4; P 2 merus as long as carapace, subequal to 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; length-breadth ratio, 4.7 on P 2, 4.1 on P 3, 3.7 on P 4; 6 rows of spines: 2 lateral, 1 ventrolateral, 1 ventromesial, 1 dorsal, 1 dorsomesial; median one of dorsal spines largest, equally long as breadth of article. Carpi with rows of prominent spines like those on meri; P 3 carpus 0.9 × length of P 2 carpus, P 4 carpus subequal to P 3 carpus; carpus-propodus length ratio, 0.6 on P 2-4; carpus-dactylus length ratio, 1.8 on P 2, 1.5 on P 3 and P 4. Propodi slightly longer on P 2 than on P 3, subequal on P 3 and P 4; extensor margin somewhat convex, with row of 6 spines paralleled laterally by smaller spines and mesially by strong spines; flexor margin with pair of terminal spines preceded by 9 spines (distal 7 in zigzag arrangement, distalmost much more remote from distal pair than from distal second on P 2). Dactyli subequal on P 2-4, 0.6 × length of carpi on P 2 and P 3, 0.7 × on P 4, and 0.4 × length of propodi on P 2-4; flexor margin very slightly curving at proximal third, with row of 10 sharp, perpendicularly directed spines, ultimate smaller than penultimate, subequal to antepenultimate.
REMARKS — This specimen was collected together with a male specimen of U. ciliatus . The antennae and eyes are so similar between these specimens that they seemed identical. However, Uroptychus quartanus is distinguished from U. ciliatus by the following particulars: the carapace and pereopods bear less numerous, relatively more pronounced spines; the excavated sternum is sharply cristate in the midline, with an triangular anterior margin, whereas it is moderately ridged and anteriorly rounded in U. ciliatus ; sternite 4 is distinctly broader than sternites 5-7 that are equally broad, whereas sternites 3-7 are successively broader posteriorly in U. ciliatus ; the abdominal somite 5 bears two anterior spines and the somite 6 is spineless, whereas both of the somites bear anterior and posterior rows of spines in U. ciliatus ; the pair of terminal spines on the P 2 propodus are more remotely separated from the next proximal spine; the P 2 merus is as long as instead of 1.4 times longer than the carapace; the P 4 merus is 1.1-1.2 instead of 0.8 times as long as the P 4 propodus; and most obviously, the ultimate of the flexor marginal spines of the P 2-4 dactyli is more slender than instead of larger than the penultimate.
Uroptychus quartanus also resembles U. senarius n. sp. in having a relatively broad and short rostrum and in having spineless abdominal somite 6. Their relationships are discussed under the account of U. senarius (see below).
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