Munidopsis bractea, Ahyong, Shane T., 2007

Ahyong, Shane T., 2007, Decapod Crustacea collected by the NORFANZ Expedition: Galatheidae and Polychelidae, Zootaxa 1593, pp. 1-54 : 5-7

Munidopsis bractea sp. nov.

( Fig. 3A , 4 )

Type material. Holotype: AM P73028, male (6.8 mm), Lord Howe Rise, 34°11.06’S, 162°39.19’E, 430–740 m, TAN0308/086 #15, 26 May 2003. Paratypes: NMNZ, 1 male (4.2 mm), 1 female (4.9 mm), southern Norfolk Ridge, 33°23.41’S, 170°11.58’E, 469–526 m, TAN0308/126 #77, 31 May 2003; NIWA 28071, 1 male (5.0 mm), southern Norfolk Ridge, 33°23.41’S, 170°11.58’E, 469–526 m, TAN0308/126 #77, 31 May 2003.

Diagnosis. Carapace dorsal outline subquadrate, surface sparsely setose, densely squamate; gastric region prominently raised; anterior gastric region inclined at about 60°, with pair of prominent epigastric scales; cardiac region prominent, squamae upraised. Rostrum spatulate, horizontal, one-third remaining carapace length. Abdominal tergites 2–4 with 2 elevated ridges separated by median transverse groove. Tergites 2 and 3 with short, blunt antrorse median projection on anterior transverse ridge. Eyes immovable, with prominent distomesial and distal squamae and shorter proximal squamae. Antennular basal segment with upright cluster of 3 or 4 evenly splayed spines on dorsal margin. Chelipeds elongate, equal, at least 1.4 times carapace length; densely squamate. Pereopods 1–3 with epipod.

Description. Carapace: 1.5 times as long as wide, moderately convex from side to side; widest at level of cardiac region; dorsal outline subquadrate, widest at level of cardiac region; surface sparsely setose, densely squamate, anterior margins of squamae crenulate or serrate; gastric region prominently raised; anterior gastric region inclined at about 60°, with field of small spines; with pair of prominent epigastric scales; cardiac region prominent, squamae upraised. Cervical groove distinct. Anterolateral margins slightly oblique; anterolateral angle squamate, with short, blunt tooth; outer orbital angle blunt, margins serrated. Lateral margins subparallel, broadly convex; without spines. Posterior margin with upraised, serrated squamae. Rostrum spatulate, horizontal; width about one-fifth distance between anterolateral angles; length one-third remaining carapace length; dorsal surface with low median carina; distal half with margins straight or slightly concave, serrated, convergent, apex blunt; proximal half with concave margins. Pterygostomian region squamate, anterior margin pointed.

Sternum: Slightly longer than wide; widest at sternite 7. Sternite 3 about 0.4 width of sternite 4; anterior margin irregularly sinuous, deeply emarginate medially; posterolateral margins rounded. Sternite 4 anterior margin sinuous, crenulate broadly convex; surface with scattered setose striae. Sternites 5–7 smooth.

Abdomen: Integument irregularly dimpled; pleura with scattered low granules. Tergites 2–4 with 2 elevated ridges separated by median transverse groove. Tergites 2 and 3 with short, blunt antrorse median projection on anterior transverse ridge. Tergites 4–6 unarmed. Telson slightly broader than long; composed of 8 plates; margins setose; surface with scattered striae. Uropodal endopod unarmed; margins setose.

Eyes: Immovable, sparsely setose, with prominent distomesial and distal squamae and shorter proximal squamae. Cornea subglobular, as wide as stalk.

Antennule: Basal segment with short distomesial spine and larger multispinose distolateral process; ventromesial surface serrate; lateral surface with oblique tuberculate row near midlength; middorsal margin with upright cluster of 3 or 4 smooth, slender, evenly splayed subequal spines.

Antenna: Basal segment with triangular, dorsally dentate distomesial tooth, overreaching segment 2; distolateral tooth blunt, reaching midlength of segment 2. Segment 3 with blunt distomesial and distalolateral tooth. Segment 4 unarmed. Flagellum not extending beyond midlength of cheliped.

Maxilliped 3: Surface squamate. Ischium extensor margin with low teeth and triangular distal tooth; with triangular flexor tooth; crista dentata with 13–15 corneous teeth. Merus extensor margin with 4 or 5 teeth; flexor margin with 4 broad, irregular teeth. Carpus extensor margin with 4 or 5 teeth, proximal smallest. Propodus squamate, as long as carpus. Dactylus unarmed, shorter than propodus.

Pereopod 1 (cheliped): Elongate, equal, 1.7–2.2 (males) and 1.4 (female) times carapace length; surfaces rugose, densely covered with raised squamae. Ischium with 1 or 2 short dorsal distal spines. Merus twice as long as carpus. Propodal palm longer than dactylus, length about 1.8 (males) and 2.0 (females) times height. Dactylus occlusal margins dentate, without gape; apices slightly hollowed, bidentate.

Pereopods 2–4: Similar, surfaces squamose; pereopods 2–4 decreasing in length posteriorly; pereopod 2 not overreaching cheliped carpus. Merus extensor and flexor margins with 1 and 2 rows of rugose, raised squamae, respectively. Carpus with short striae; extensor margin with upright tubercles and squamae, largest distally; flexor margin unarmed. Propodus about 4 times as long as high; with denticulate surfaces and margins; with extensor margin irregularly tuberculate or spinose, with blunt distal tooth; with minute, movable, distal flexor spine. Dactylus about half (largest specimen) to two-thirds propodus length (smallest specimen); extensor margin minutely spinose on proximal half; flexor margin with 10–12 movable spines and corneous unguis.

Epipods: Pereopods 1–3 with epipod.

Colour in life. Overall deep to pale orange, palest in largest specimens.

Etymology. Derived from bractea, Latin for scale or plate, alluding to the squamose ornamentation of the carapace.

Remarks. Munidopsis bractea sp. nov. is morphologically similar to M. proales Ahyong & Poore, 2004 , M. tasmaniae Ahyong & Poore, 2004 , M. sonne Baba, 1995 , M. taurulus Ortmann, 1892 , and M. papanui Schnabel & Bruce, 2006 , in the strongly rugose dorsum that is densely covered with tubercles or squamae. The new species, however, is readily distinguished from each of the aforementioned species by its much higher gastric region in which the anterior gastric surface is inclined at about 60° to the horizontal, rather than 45° or less. Of these rugose species, M. bractea is most similar to M. papanui from New Zealand: both have a basal antennular segment with a multispinose dorsal margin, ill-defined or absent lateral carapace teeth, and a median antrorse projection on abdominal tergites 2 and 3 (albeit much less pronounced in M. bractea than in M. papanui ). Other than the height of the gastric region, M. bractea differs from M. papanui in numerous features including the squamate rather than tuberculate carapace surface, irregular rather than straight rostral margins, and relatively transverse rather than distinctly oblique anterior margin of sternite 4. Sexual dimorphism in M. bractea is expressed in cheliped size, being longer and more robust in the largest male (holotype) than in the female and other paratypes.

Distribution. Lord Howe Rise and southern Norfolk Ridge; 430– 740 m.

Figures

FIGURE 4. Munidopsis bractea sp. nov., holotype male, 6.8 mm (AM P 73028). A, left lateral view. B, dorsal view. C, left basal antennular segment, lateral view. D, left antennule and antenna, ventral view. E, right third maxilliped, lateral view. F, sternum. G, telson. H, left pereopod 2. I, left cheliped, lateral view. J, left cheliped fingers, mesial view. Scale: A, B, H – J = 2.0 mm; C – G = 1.0 mm.

FIGURE 3. A, Munidopsis bractea sp. nov. paratype female, 4.9 mm, TAN 0308 / 126 (NMNZ). B, Munidopsis norfanz sp. nov., holotype, TAN 0308 / 066 (AM). C, Munidopsis treis Ahyong & Poore, 2004, female, 10.7 mm, TAN 0308 / 154 (NMNZ).