Cymonomus confinis, Ahyong, 2019

Ahyong, Shane T., 2019, The Cymonomid Crabs of New Zealand and Australia (Crustacea: Brachyura: Cyclodorripoida), Records of the Australian Museum 71 (2), pp. 33-69 : 46-48

Cymonomus confinis sp. nov.

http://zoobank.org/NomenclaturalActs/ 37AFC73F-4124-4327-8EDB-59C5806C3DAB

Figs 12 , 13

Holotype: NMV J52177 , male (cl 3.2 mm, pcl 2.7 mm, cw 2.9 mm), Great Australian Bight , South Australia, Australia, 33°15.87'S 130°37.83'E, Yvonne Bone sled, 139 m, SS10/00/334, RV Southern Surveyor, 9 May 2000.

Description of holotype. Carapace quadrate, almost square, lateral margins weakly divergent posteriorly; regions weakly indicated, cervical groove weakly indicated; lower pterygostomian region swollen; anterior and anterolateral surfaces with few long, fine setae, other surfaces sparsely setose. Anterolateral spine prominent, directed anteriorly; smaller spine on lateral margin behind anterolateral spine. Anterior carapace margin mesial to the anterolateral spine sloping posteriorly towards midline, with short spinules, acute granules. Dorsal and lateral surfaces densely covered with minute granules; few, scattered spinules anteriorly. Frontoorbital margin (excluding rostrum and lateral projections) advanced beyond anterolateral margins; 0.6 anterior carapace width; outer orbital processes sharply triangular, elongate, divergent, directed anterolaterally, situated below plane of rostrum, dorsally and laterally granulate, few spinules, apex acute, shorter than rostrum. Rostrum length about two-thirds length of eyestalks; 0.17 pcl; slender, triangular, sparsely granulate dorsally and laterally.

Eyestalks weakly divergent (18° to median axis), strongly tapering, ventrally flattened, fused to carapace below rostral base but demarcation distinct; reaching anteriorly to distal ¾ of antennular peduncle article 1; dorsal surface sparsely granulate, lateral and mesial margins weakly spinulate; cornea apparently vestigial, not pigmented.

Epistome with tubercle at base of rostrum and tubercle mesial to base of antennules; with slender spine mesial to base of antenna.

Antennular peduncle 0.75 pcl (male); articles 1 and 2 minutely granulate; article 3 smooth. Antennal articles granulate or spinose.

Maxilliped 3 ischiobasis subquadrate, surface and margins sparsely granulate, with few acute granules or short spines; shallow longitudinal sublateral groove; ischium and basis demarcated by faint groove. Merus longer than ischium, as long as ischiomerus; length 2.9 × width (excluding spines); tapering distally to rounded apex; surface and margins bluntly spinulate. Dactylus, propodus and carpus granulate or spinulate. Exopod granulate, spinulate, not distally reaching 2/3 length of endopod merus.

Chelipeds (pereopod 1) equal in size and ornamentation, sparsely setose, almost glabrous. Merus finely granulate, with few short distal and ventral spines. Carpus granulate, spinose, spines slender, conical to allantoid. Propodus palm surfaces and margins with numerous long, blunt, allantoid spines, few conical spines, extending onto pollex. Dactylus as long as dorsal palm length; proximal two-thirds spinose; outer surface with faint longitudinal carina, sparsely granulate, occlusal surfaces of dactylus and pollex crenulate, slight gape when fingers closed.

Pereopods 2 and 3, sparsely setose, flexor and extensor margins granulate and spinose, other surfaces sparsely granulate; longest spines on extensor margins and dorsal surfaces of propodus and carpus; merus extensor and flexor margins with short spines; dactylus broadly curved, sparsely and minutely spinulate proximally, otherwise smooth, with distinct longitudinal rib. Pereopod 3 longest, merus as long as carapace, 1.00 pcl (male); dactylus shorter than combined length of propodus and carpus.

Pereopods 4 and 5 finely granulate, sparsely spinose; longer than pereopod 3 merus (male); propodus distoextensor margin unarmed; dactylus markedly shorter than propodus, falcate, with corneous apex and 4 obliquely inclined, corneous spines on flexor margin. Pereopod 5 merus, when folded against carapace, reaching midlength of carapace.

Thoracic sternite 3 pentagonal, width twice length; lateral proximal margins parallel; surface unadorned. Margins of sternites 4 and 5 granulate.

Abdomen very sparsely granulate, minutely spinose on lateral surfaces. Pleotelson without trace of demarcation between somite 6 and telson; semi-ovate, unadorned; apex broadly rounded; width 2.1 × length (male).

Gonopod 1 distal article cannulate, forming copulatory tube, apex slightly fluted, with moderately long distal setae. Gonopod 2 with articles fused; distomesial margin slightly hollowed, apex acute.

Etymology. From the Latin adjective, confinis , neighbouring, alluding to the Australian occurrence of the new species, adjacent to its close New Zealand relative, C. bathamae .

Remarks. Cymonomus confinis sp. nov., a member of the C. bathamae species group, is closest to C. brevis sp. nov. and C. bathamae Dell, 1971 , from New Zealand, differing from both in the weakly tapering eyestalks with outer margins subparallel for most of their length ( Fig. 12D ) (versus strongly divergent; Figs 6D , 8D ), shorter maxilliped 3 exopod ( Fig. 12E ) (reaching to the distal three-fourths, rather than distinctly overreaching the merus; Figs 6E , 8E ) and shorter pereopod 5 (merus reaching anteriorly to the midlength, rather than to the anterior one-third of the carapace; Fig. 12A versus Fig. 8A ). Other distinctions between the regional members of the C. bathamae species group are outlined under the account of C. espinosus .

Distribution. Presently known only the Great Australian Bight, South Australia ( Fig. 13 ); 139 m.

Figures

Figure 6. Cymonomus bathamae Dell, 1971. (A–F) spent female paratype, cl 3.9 mm, pcl 3.3 mm, cw 3.6 mm, Chatham Rise, New Zealand, NIWA 68007. (G–I) male, cl 6.0 mm, pcl 3.3 mm, cw 3.5 mm, Chatham Rise, New Zealand, NIWA 31653. (J) ovigerous female paratype, cl 4.4 mm, pcl 3.7 mm, cw 4.1 mm, off Otago, New Zealand, NIWA 68021. (A) dorsal habitus; (B) posterior abdomen; (C, J) right epistomial spine mesial to base of antenna; (D) fronto-orbital region; (E) right maxilliped 3; (F) thoracic sternite 3; (G) right G1, abdominal view; (H) right G2, abdominal view; (I) pleotelson. Scale:A–B = 2.0 mm; C, J = 0.5 mm; D–I = 1.0 mm.

Figure 8. Cymonomus brevis sp.nov., female holotype, cl 3.9 mm, pcl 2.8 mm, cw 3.3 mm, Bay of Plenty, New Zealand, NIWA 76191. (A) dorsal habitus; (B) posterior abdomen; (C) right epistomial spine mesial to base of antenna; (D) fronto-orbital region; (E) right maxilliped 3; (F) thoracic sternite 3. Scale: A–B = 1.0 mm; C = 0.25 mm; C–F = 0.5 mm.

Figure 12. Cymonomus confinis sp. nov., male holotype, cl 3.2 mm, pcl 2.7 mm, cw 2.9 mm, Great Australian Bight, South Australia, NMV J52177. (A) dorsal habitus; (B) abdomen; (C) right epistomial spine mesial to base of antenna; (D) fronto-orbital region; (E) right maxilliped 3; (F) thoracic sternite 3; (G) left G1, abdominal view; (H) left G2, abdominal view. Scale:A–B = 1.0; C–H = 0.5 mm.

Figure 13. Cymonomus confinis sp. nov., distribution.