Uroptychus brevirostris Van Dam, 1933

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 : 121-124

Uroptychus brevirostris Van Dam, 1933

Figure 46

Uroptychus brevirostris Van Dam, 1933: 20 , figs 29-32. — Van Dam 1940:96. — Baba 2005 (synonymies, key).

Not Uroptychus brevirostris: Baba 1973:117 (= U. alcocki Ahyong & Poore, 2004 ).

TYPE MATERIAL — Holotype: Indonesia, Sulu Archipelago , 5°43.5’N, 119°40’E, 522 m female ( ZMA De. 101.694). [examined].

MATERIAL EXAMINED — Philippines. MUSORSTOM 3 Stn CP133, 11°58’N, 121°52’E, 334-390 m, with Chrysogorgiidae gen. sp. ( Calcaxonia ), 5.VI.1985, 1 ov. ♀ 5.4 mm (MNHN-IU-2014-16342), 1 ♂ 4.0 mm, 1 ov. ♀ 6.0 mm, 1 sp. (sex indet.) 2.4 mm (MNHN-IU-2014-16343).

DISTRIBUTION„ Sulu Archipelago and Java Sea, in 41-520 m, and now northeastern Panay, Philippines, in 334- 390 m.

DESCRIPTION„ Medium-sized species. Carapace: As long as broad; greatest breadth 1.8 × distance between anterolateral spines. Dorsal surface well convex from side to side and anterior to posterior, without depression between gastric and cardiac regions, smooth and glabrous. Epigastric region with pair of denticulate short ridges. Lateral margins weakly divergent posteriorly, convex posteriorly, with well-developed anterolateral spine overreaching small lateral orbital spine. Rostrum subtriangular, with interior angle of 22-30°, dorsally flattish, ventrally straight horizontal; length 0.3 × that of remaining carapace, breadth about half carapace breadth measured at posterior carapace margin; lateral margins slightly concave. Lateral orbital spine much smaller than, located slightly anterior to level of, and more or less close to, anterolateral spine. Pterygostomian flap anteriorly somewhat roundish, ending in small spine; surface smooth.

Sternum: Excavated sternum strongly produced anteriorly, ending in sharp spine; surface with spine in center. Sternal plastron slightly broader than long, gradually broadened posteriorly; relatively long setae on transverse ridges and lateral margins of sternites 5-7. Sternite 3 deeply depressed, anterior margin deeply emarginate, with pair of submedian spines contiguous at base, without median notch. Sternite 4 with more or less convex anterolateral margin anteriorly produced to short spine followed by granules, posterolateral margin short, about half length of anterolateral margin. Anterolateral margins of sternite 5 convexly divergent posteriorly, about as long as posterolateral margin of sternite 4.

Abdomen: Nearly glabrous and smooth. Somite 1 with antero-posteriorly convex. Somite 2 tergite 2.5 × broader than long; pleural lateral margin slightly concavely divergent posteriorly, ending in rounded terminus. Pleuron of somite 3 posterolaterally blunt. Telson slightly more than half as long as broad; posterior plate 1.7 × longer than anterior plate, posterior margin distinctly emarginate.

Eye: Relatively broad (length 1.6 × breadth), slightly broadened proximally, slightly falling short of apex of rostrum. Cornea not dilated, more than half length of remaining eyestalk.

Antennule and antenna: Antennular ultimate article 1.7-2.0 × longer than high. Antennal peduncle terminating in distal corneal margin. Article 2 with small distolateral spine. Antennal scale slightly broader than article 5, slightly falling short of or reaching distal end of peduncle. Articles 4 and 5 unarmed; article 5 1.5-1.9 × longer than article 4, breadth half height of ultimate article of antennule. Flagellum consisting of 12-14 segments (9 in smallest specimen), not reaching distal end of P1 merus.

Mxp: Mxp1 with bases nearly contiguous. Mxp3 smooth, glabrous on lateral surface. Basis with 4 denticles on mesial ridge. Ischium not rounded at distal end of flexor margin; crista dentata with 14-15 denticles. Merus and carpus unarmed; merus 1.9 × longer than ischium.

P1: Massive, smooth, very setose on fingers, glabrous on ischium and merus; length 4.2-4.5 × that of carapace. Ischium with basally broad, short dorsal spine, ventromesial margin with row of denticle-like spines on proximal half, lacking subterminal spine. Merus slightly (1.1 ×) longer than carapace, mesially bearing several tubercle-like spines on proximal portion, ventrally a few proximal tubercles. Carpus 1.1-1.2 × longer than merus. Palm 2.2 × longer than broad, subequal to or slightly shorter than (0.9) carpus. Fingers very setose, distally not sharply pointed, not distinctly incurved; opposable margin of movable finger with depressed, broad proximal process bearing 2 obtuse teeth; movable finger 0.6 × length of palm.

P2-4: Smooth, relatively broad, with long setae especially numerous on mesial faces of propodi and dactyli; P4 much shorter and narrower than P2 and P3. Meri strongly compressed mesio-laterally and distally narrowed, very slightly shorter on P3 than on P2, subequally broad on P2 and P3, smallest on P4 (P4 merus 0.7 × length and 0.7 × breadth of P3 merus); length-breadth ratio, 3.5-3.6 on P2, 3.4-3.5 on P3, 3.5-3.6 on P4 (in smallest specimen: 4.9, 4.7, 4.4 respectively); P2 merus 0.9 × length of carapace, 1.1 × length of P2 propodus; dorsal margin with very small denticles or granules on proximal third on P2, obsolete on P3 and P4; P3 merus as long as P3 propodus; P4 merus 0.9 × length of P4 propodus. Carpi subequal in length on P2 and P3, much shorter on P4 (P4 carpus 0.7-0.8 × length of P3 carpus), 0.6 × length of propodus on P2-3, 0.5-0.6 × on P4; unarmed. Propodi subequal in length on P2 and P3, shortest on P4; flexor margin straight, with pair of terminal spines preceded by row of 7 or 8 spines on P2-3 (6 on smallest specimen), 6 or 5 on P4. Dactyli proportionately broad proximally and distally, length 0.4 × that of propodi on P2 and P3, 0.4-0.5 × on P4, and 0.6-0.7 × length of carpi on P2, 0.7 × on P3, 0.8 × on P4; strongly curving at proximal quarter; flexor margin with 9 or 10 spines, obscured by setae

in large specimens, ultimate longest, penultimate about as broad as or slightly narrower than ultimate, remaining spines proximally diminishing and oriented parallel to flexor margin.

Eggs. Number of eggs carried, 11 in larger female; size, 0.58 × 0.59 mm - 0.60 × 0.66 mm (yolky); 14 eggs in smaller female; size, 1.06 × 0.97 mm.

REMARKS — The specimens agree quite well with the original description of U. brevirostris Van Dam, 1933 , except that the rostral margin is somewhat concave. Examination of the type material shows that the P2-4 dactyli bear flexor spines oriented parallel to the dactylar margin, not as illustrated by Van Dam (1933: fig. 32) (see Figure 46M ). The presence or absence of the epigastric ridges in the type has not been confirmed.

Uroptychus brevirostris strongly resembles U. disangulatus n. sp. in the shape of the carapace, pterygostomian flap, sternal plastron and P2-4 dactyli. Their relationships are discussed under the remarks of that species (see below).

Uroptychus brevirostris somewhat resembles U. australis ( Henderson, 1885) in the spination of P2-4 dactyli and in having short P4s, from which it is readily distinguished by the following differences: the carapace is as long as instead of distinctly longer than broad, and the rostrum is about as long as instead of much longer than broad; the anterolateral spine of the carapace is closer to instead of moderately remote from the lateral orbital spine, when viewed from dorsal side; P1 is more massive, with the palm short relative to breadth (length 2.3 times breadth in U. brevirostris , more than 3 times in U. australis ); and the P4 merus is 0.7-0.8 instead of at most 0.6 times the length of P3 merus.

Figures

FIGURE 46 Uroptychusbrevirostris Van Dam,1933,A-L, ovigerous female5.4 mm (MNHN-IU-2014-16342);M, holotype,female (ZMA De.101.694). 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, left antenna, ventral. E, right Mxp3, setae omitted, lateral. F, same, ventral. G, left P1, proximal part, ventral. H, same, dorsal. I, right P2, lateral. J, same, distal part, setae omitted, lateral. K, right P3, distal part, lateral. L, right P4, distal part, lateral.M, right P2, distal part, lateral. Scale bars: 1 mm.