Munidopsis arenula, Published, 2007

Published, First, 2007, Species of the genus Munidopsis Whiteaves, 1784 from the Indian and Pacific Oceans and reestablishment of the genus Galacantha A. Milne-Edwards, 1880 (Crustacea, Decapoda, Galatheidae), Zootaxa 1417, pp. 1-135 : 38-41

Munidopsis arenula n. sp.

( Fig. 20)

Material examined. New Caledonia, BIOGEOCAL, Stn 291, 510– 520 m: 1 F 4.6 mm, holotype (MNHN- Ga5557) .

Etymology. From the Latin arenula , grain of sand, in reference to the numerous granules on the dorsal carapace surface. The name is considered as a substantive in apposition.

Description. Carapace slightly longer than broad; dorsal surface moderately convex from side to side, covered with small acute granules, nearly devoid of setae; 4 small epigastric spines and some minute spines on anterior branchial regions; regions well delineated by furrows including distinct anterior and posterior cervical grooves. Median branchial region well marked. Posterior cardiac region bluntly triangular, preceded by deep transverse depression on each side. Posterior margin preceded by granulated ridge. Rostrum narrow triangular, horizontal in lateral view, 0.3 times length of remaining carapace, and 0.2 times as wide as carapace breadth, dorsal surface with longitudinal carina, ending at base of rostrum; lateral margins carinate. Frontal margin with antennal spine, concavely transverse behind ocular peduncle, slightly oblique between antennal spine and anterolateral corner of carapace. Lateral margins granulated, weakly convex and subparallel, anterolateral angle with small spine, clearly smaller than antennal spine, two small spines on anterior branchial margin; end of anterior cervical groove with distinct notch, end of posterior cervical groove with shallow notch, followed by small spines.

Ptergostomian region granulated, anteriorly ending in acute angle.

Sternum as long as wide, maximum width at level of sternite 7. Sternite 3 moderately broad, 2.5 times broader than long, anterior margin divided into 2 lobes by median notch, lateral margin of each lobe convex. Sternite 4 wide anteriorly; surface depressed in midline, with some short ridges on anterior part; greatest width nearly 2.5 times that of sternite 3.

Abdomen smooth, unarmed; segments 2ñ4 each with 2 slightly elevated transverse ridges, but segments 5–6 lacking such ridges; segment 6 with weakly produced posterolateral lobes and nearly transverse posteromedian margin. Telson composed of 7 plates; posterior plates combined nearly 1.5 times as wide as long.

Ocular peduncle scarcely movable, with short mesial spine; cornea subglobular, slightly narrower than eyestalk, without spine or tooth between eye and antennal peduncle.

Basal article of antennular peduncle with dorsolateral and distolateral spines; distomesial margin with crest of granules and small spine.

Antennal peduncle reaching tip of eye; article 1 with distomesial and distodorsal spines; article 2 with 2 small distal spines on mesial and lateral margins; article 3 with granulated distal margin; article 4 unarmed.

Mxp 3 ischium as long as merus measured on extensor margin; merus with flexor margin with 2 strong spines and several granules; extensor margin with small distal spine; 19 or 20 corneous denticles on crista dentata.

P1 moderately long and slender, nearly devoid of setae, ca. 1.5 times longer than carapace, covered with small granules on merus to dactylus, those on fingers reduced in number. Merus twice carpus length, with 2 spines at midlength and at distal part of mesial margin, a few minute spines on dorsal side. Carpus more than twice longer than high, with row of small mesial spines, and small dorsolateral distolateral spines. Palm unarmed, slender, 1.3 times length of carpus, and as long as fingers. Fingers unarmed, opposable margins nearly straight, not gaping, distally spooned.

P2–P4 slender, nearly devoid of setae, somewhat compressed laterally, decreasing in size posteriorly; P2 longest, not reaching end of P1. P2 merus moderately elongate, 0.6 times length of carapace, 3.5 times longer than high, nearly twice carpus length, dorsal margin with row of small spines, increasing in size distally; lateral surface with small granules; ventral margin serrated; carpus with serrated crest along dorsal margin and lateral surface; propodus slightly shorter than merus, 6 times longer than high and nearly twice dactylus length, covered with numerous small granules, one movable distal spinule on ventral margin; dactylus weakly curved; flexor margin straight, with 9 or 10 teeth decreasing in size proximally, each with slender corneous spinule.

Epipods absent from P1–P4.

Remarks. The new species most closely resembles M. acutispina Benedict, 1902 , from the northeastern Atlantic and Mediterranean Sea, at 698–2030 m ( Froglia et al. 2002; Macpherson & Segonzac 2005). Both species are characterized by the carapace being convex from side to side, with numerous pointed tubercles, the rostrum narrow triangular, its basal width less than one-third the anterior width of carapace, the antennal spine small, segments 2 and 3 of the abdomen unarmed, the cornea well exposed, visible in dorsal view, the eye spine mesial and small, the walking legs not reaching the end of the chelipeds, and the pereiopods without epipods.

A comparison with the Atlantic material of M. acutispina (types from the Talisman Expedition, northwestern Africa at 698 m, 2 M 5.3–8.2 mm, 1 ovig. F 7.8 mm, 2 F 4.4–5.7 mm, MNHN-Ga 275, 276, see also Macpherson & Segonzac 2005) showed that they can be easily differentiated by the armature of the dorsal surface of the carapace. In the new species, the carapace is covered with granules, bearing a few small epigastric and anterobranchial spines, whereas the carapace surface is covered with numerous acute spines in M. acutispina . Furthermore, the spines along the lateral margins of the carapace are always stronger in M. acutispina than in M. arenula .

The new species is also close to M. proales Ahyong & Poore, 2004 , from western Australia, at 513–540 m. This species is readily distinguished by the presence of epipods on P1–P3, which are absent in the new species .

Distribution. New Caledonia, at 510– 520 m.