Uroptychus brachydactylus Tirmizi 1964
Creators: name: Baba, Keiji
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Chirostylidae
Uroptychus
Uroptychus brachydactylus

description: Uroptychus brachydactylus Tirmizi, 1964
Figures 43-45
Uroptychus brachydactylus Tirmizi, 1964: 399,fig. 19.
TYPE MATERIAL — Holotype: South Arabian coast, JOHN MURRAY Stn 42, 1415 m, male (BMNH 1966.2.3.20). [examined].
MATERIAL EXAMINED — New Caledonia, Isle of Pines. BIOGEOCAL Stn CP232, 21°33.81’S, 166°27.07’E, 760-790 m, 12.IV.1987, 1 ♂ 14.7 mm (MNHN-IU-2014-16341).
DISTRIBUTION„ South Arabian coast and now Isle of Pines; 760-1415 m.
DESCRIPTION„ Large species. Carapace: 1.1 × longer than broad; greatest breadth 2.0 × distance between anterolateral spines. Dorsal surface glabrous, feebly granulose, weakly convex from anterior to posterior, bearing very weak depression between gastric and cardiac regions. Lateral margins convexly divergent posteriorly, with row of short granulate ridges, and ridged along posterior fourth of length; anterolateral spine small, reaching distal end of antennal article 2, relatively remote from, slightly posterior to level of, and slightly overreaching small lateral orbital spine. Rostrum elongate sharp triangular, with interior angle of 23°; length slightly more than one-third that of carapace, breadth less than half carapace breadth measured at posterior carapace margin; dorsal surface flattish. Pterygostomian flap granulose, anteriorly roundish, with small spine.
Sternum: Excavated sternum anteriorly ending in small distinct spine, surface with small central spine. Sternal plastron as long as broad, lateral extremities posteriorly divergent. Sternite 3 with deep depression expanded posteriorly on to sternite 4; anterior margin deeply excavated, with pair of submedian spines separated by narrow deep notch. Sternite 4 granulose on surface; anterolateral margin longer than distance between anterolateral angles of sternite 3, 1.6 × length of posterolateral margin, anteriorly ending in distinct spine. Anterolateral margin of sternite 5 anteriorly convex, 1.4 × longer than posterolateral margin of sternite 4.
Abdomen: Smooth and glabrous. Somite 1 well convex from anterior to posterior. Somite 2 tergite 2.9 × broader than long; pleuron posterolaterally bluntly angular, lateral margin strongly concave. Pleuron of somite 3 posterolaterally angular. Telson about half as long as broad; posterior plate somewhat emarginate on posterior margin, length 1.4 × that of anterior plate.
Eye: Elongate, overreaching midlength of rostrum, laterally and mesially concave proximal to cornea; length about twice breadth. Cornea more than half length of remaining eyestalk.
Antennule and antenna: Ultimate article of antennular peduncle 3 × longer than high. Antennal peduncle slightly overreaching cornea. Article 2 with small distolateral spine. Antennal scale slightly more than twice as broad as opposite peduncle, terminating in distal quarter of article 5, overreaching cornea. Distal 2 articles slender, unarmed; article 5 2.6 × longer than article 4, breadth half height of ultimate article of antennule. Flagellum of 18 segments barely reaching distal end of P1 merus.
Mxp: Mxp1 with bases close to each other but not contiguous. Mxp3 basis with 4 denticles on somewhat convex mesial ridge, distalmost largest. Ischium with flexor margin not rounded distally, crista dentata with 26 or 27 denticles distally diminishing. Merus 2.4 × longer than ischium, relatively narrow, moderately thick mesio-laterally, unarmed, flexor margin ridged but not sharply crested. No spine on carpus.
P1: Relatively massive, setose distally. Ischium with low, broad, dorso-ventrally depressed, plate-like process dorsally, without spines on ventromesial margin. Merus covered with short granulate ridges, length slightly more than that of carapace. Carpus somewhat granulose, 1.4 × longer than merus, subcylindrical but somewhat ridged along dorsomesial and dorsolateral margins, distally broadened. Palm 2.4 × longer than broad, slightly shorter than carpus, smooth and
glabrous, depressed well, distally broadened, greatest breadth 2.2 × that of carpus measured at midlength; dorsal and ventral surfaces convex, ridged along lateral and mesial margins, mesial margin crested. Fingers distally crossing, ending in short sharp spine; opposable margins fitting to each other in distal half (in distal third in holotype), gaping in proximal half; movable finger with broad low process on gaping portion, length about half that of palm.
P2-4: Slender, moderately compressed, with sparse long setae. Meri successively shorter posteriorly (P3 merus 0.9 × length of P2 merus; P4 merus 0.8 × length of P3 merus), equally broad on P2-4; length-breadth ratio, 6.9 on P2, 6.7 on P3, 5.3 on P4; P2 merus slightly shorter than carapace, 1.5 × longer than P2 propodus, dorsal margin unarmed, ventrolateral margin with small distal spine; P3 merus 1.2 × length of P3 propodus; P4 merus as long as P4 propodus. Carpi successively shorter posteriorly (P3 carpus 0.9 × length of P2 carpus, P4 carpus 0.9 × length of P3 carpus); length 0.7 × that of propodus on P2, 0.6 × on P3 and P4. Propodi subequal on P2-4 or subequal on P2-3 and longer on P4; flexor margin ending in pair of spines preceded by 9 or 10 spines on P2, 11 on P3, 7 or 9 on P4. Dactyli subequal on P2-4, 0.3 × length of propodi, 0.4 × length of carpi on P2 and P3, 0.5 × on P4; distally slender, strongly curving at proximal third; flexor margin with 10 or 11 (12 on P 4 in holotype) somewhat inclined, sharp, proximally diminishing spines.
REMARKS — The penultimate of the flexor marginal spines of dactylus is smaller than the antepenultimate on the left P2, but those on the other appendages including P3 and P4 are larger, presumably regenerated after being broken.
The material generally agrees with the description of the male holotype of U. brachydactylus Tirmizi, 1964 previously known from the western Indian Ocean. However, the following slight differences are found by examination of the holotype (BMNH 1966.2.3.20; Figure 45). In the present material, the antennal scale falls short of instead of reaching the tip of article 5, and article 2 bears a tiny rather than distinct distolateral spine; the P1 palm and fingers are smooth instead of noticeably granulose; the P4 propodus bears flexor marginal spines along the distal three-fifths of the length instead of the distal quarter; and the posterolateral margin of sternite 4 is relatively short, 0.8-0.9 instead of 1.3 times as long as the anterolateral margin of sternite 5. The last mentioned difference may indicate this specimen is a separate species, as is shown by U. longioculus Baba, 1990 from Madagascar and U. poupini n. sp. from Fiji, Tonga and New Caledonia, the separation of which are based only on the length-breadth ratio of sternite 4 and supported by DNA analyses (see below under U. poupini). The present material is provisionally placed in U. brachydactylus, awaiting more material to allow genetic analyses.
Uroptychus brachydactylus resembles U. brucei Baba, 1986a. Their relationships are discussed under that species (see below).
description: Published as part of Baba, Keiji, 2018, Chirostylidae of the Western and Central Pacific: Uroptychus and a new genus (Crustacea: Decapoda: Anomura), pp. 1-612 in Mémoires du Muséum national d'Histoire naturelle 212 on pages 117-121, DOI: 10.5281/zenodo.3760976