Munidopsis atlantis, Ahyong, 2014

Ahyong, Shane T., 2014, Deep-sea Squat Lobsters of the Munidopsis serricornis Complex in the Indo-West Pacific, with Descriptions of Six New Species (Crustacea: Decapoda: Munidopsidae), Records of the Australian Museum (Rec. Aust. Mus.) 66 (3), pp. 197-216 : 200-202

Munidopsis atlantis sp. nov.

Figs 2 , 9

Type material. HOLOTYPE: OUMNH. ZC.2013-01-007, ovigerous female (cl 9.8 mm, pcl 6.8 mm), Atlantis Bank, Southwest Indian Ridge, 32°42.862'S 57°14.666'E, 1117 m, RRS James Cook cruise JC066, ROV Keel 6000, 10 December 2011.

Diagnosis. Rostrum broad, flat, medially carinate, trifid distally. Carapace with pair of epigastric spines, otherwise unarmed dorsally; surface of dorsal half with granules and short rugae; lateral margins with 4 spines (1 anterolateral, 3 branchial); posterior orbital margin transverse; outer orbital spine distinct. Abdominal tergites unarmed. Telson with 8 plates. Maxilliped 3 merus flexor margin with 2 spines. Cheliped carpus length twice width, dorsal surface unarmed. Walking leg meri irregular to serrated along extensor margin; dactylus flexor margin with movable spines, and more slender movable spine at base of corneous unguis. Pereopods without epipods.

Description. Carapace: Moderately convex from side to side; surface with few scattered short setae, almost glabrous; surface of anterior half with granules and small rugae or short striae; surface of posterior half with short striae. Cervical groove indistinct. Pair of epigastric spines flanked by short scales. Posterior orbital margins transverse, outer orbital spine prominent. Frontal margins oblique, concave; anterolateral spine similar to outer orbital spine. Lateral margins subparallel; with 2 spines on anterior branchial margin and blunt spine at junction of anterior and posterior branchial margins. Rostrum broad, 0.4 pcl; trifid distally; apex horizontal; median carina distinct; lateral proximal margin weakly convex, tapering. Posterior margin unarmed, shallowly concave medially. Pterygostomian flap with short diagonal striae posteriorly and short rugae anteriorly; anterior margin blunt, angular.

Sternum: Sternite 3 about 0.3 width of sternite 4. Posterior margin of sternite 3 contiguous with anterior margin of sternite 4. Sternites smooth, sparsely setose, unarmed.

Abdomen: Tergites unarmed; surface with few scattered setae, almost glabrous. Tergites 2–4 with elevated anterior ridge; tergites 2 and 3 also with shallow groove behind anterior ridge. Tergites 4–6 smooth; posterior margin not strongly produced. Telson composed of 8 plates (minute central plate present). Uropodal endopod lateral margins setose, unarmed.

Eye: Ocular peduncle unarmed, glabrous; movable; partially concealed by rostrum. Cornea subglobular, slightly wider than peduncle. Small, slender spine adjacent to lateral margin of eye.

Antennule: Basal article squat, with 2 distolateral spines, dorsal shorter; distomesial margin with short triangular tooth.

Antenna: Basal article with triangular mesial and lateral tooth, neither overreaching article 2. Article 2 with strong distolateral spine, reaching midlength of article 3. Articles 3 and 4 unarmed. Flagellum 1.2 pcl.

Maxilliped 3: Dactylus, propodus and carpus unarmed. Merus extensor margin with distal spine; flexor margin with 2 large triangular spines proximally and 2 low tubercles distally. Ischium longer than wide, with acute distal flexor and extensor angles. Crista dentata with 26–30 denticles.

Pereopod 1 (cheliped): Cheliped elongate, 2.7 pcl, sparse simple golden setae, most numerous on dorsal and ventral margins; subcylindrical to ovate. Ischium with dorsal spine; without ventral spine. Merus with row of 4 or 5 small, graded, well-spaced dorsal spines and large distal dorsal spine; mesial margin with 2 large spines, one distally at carpal articulation, one at distal one-third of margin; ventromesial margin with 2 strong proximal spines and distal spine. Carpus length about 2 times width; mesial margin with distal and subdistal spine, latter largest; small dorsodistal and ventrodistal spine. Propodus unarmed, palm about 2.7 times as long as wide; mesial margin of palm longer than dactylus. Pollex and dactylus occlusal margins crenulated, apices with interlocking teeth, small proximal gape on dactylus. Epipod absent.

Pereopods 2–4: Slightly compressed; decreasing in length posteriorly; with scattered, setose striae. Merus elongate; length 3.4 times width (pereopod 2) to 2.8 (pereopod 4); extensor margin irregular to serrated but not spinose; distal extensor margin with large distal spine; flexor margin irregular but not spinose except for triangular distal spine. Carpus with distal extensor spine and irregular to serrated margin; low, irregular, dorsal carina. Propodus extensor margin irregular, unarmed; flexor margin with movable spine at distal one-third and paired movable spines distally adjacent to dactylar articulation. Dactylus about two-thirds propodus length; extensor margin with scattered setae, unarmed; flexor margin with 9 or 10 low triangular teeth, each bearing corneous movable spine and more slender movable spine at base of corneous unguis. Epipods absent.

Egg diameter: 1.5 mm.

Colour in life. Unknown.

Etymology. From the type locality, Atlantis Bank; used as a noun in apposition.

Remarks. Munidopsis atlantis sp. nov. is most similar to M. comarge and M. ternaria in the combination of a granulated and rugose anterior half of the carapace and serrated but not spinose extensor meral margins of the walking legs. It resembles M. ternaria (and differs from M. comarge ) in having epigastric spines and differs from both species in having lateral carapace spines behind the anterolateral spine. Munidopsis atlantis and M. macphersoni differ in the number of lateral spines on the carapace behind the anterolateral spine, three in the latter, four in the former. Munidopsis atlantis is also superficially similar to M. crinita Faxon, 1893 , from the eastern Pacific in sharing the presence of epigastric spines and unarmed extensor margins of the meri of the walking legs, but is readily distinguished by the glabrous or sparsely setose, rather than, densely setose body and chelipeds.

Macpherson et al. (2014) recently described Munidopsis mandelai from Atlantis Bank and Middle of What Seamount at 703–1135 m depth; it is readily distinguished from M. atlantis in the absence of lateral rostral spines and presence of eyespines.

Distribution. Presently known only from Atlantis Bank, Southwest Indian Ridge; 1117 m.

Figures

Figure 2.Munidopsis atlantis sp. nov., ovigerous female holotype, cl 9.8 mm, pcl 6.8 mm (OUMNH.ZC.2013-01-007).(A) dorsal habitus; (B) carapace, right lateral view; (C) right antenna and antennule, ventral view; (D) right basal antennular article, lateral view; (E) right maxilliped 3; (F) right crista dentata; (G) right cheliped finger tips, ventral view; (H) right cheliped ischiomerus, lateral view; (I) right ischiomerus, mesial view; (J) sternal plastron; (K) telson. Scale:A, B, G–I = 2.0 mm; C–F, J, K = 1.0 mm.