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Cycloachelous levigatus, sp. nov. All collected from Cuẩ Bé fishing port (12° 20‘ N, 109° 12‘ E), north off Nhatrang, Khanh Hoa Province, Vietnam. Holotype: 1♂ CW 23 mm, MNHN-IU-2014-10093, [GenBank n. MZ 127805], 27 Jun. 2012, fcn UO 12 Pa- Vn 12, coll. Z. Ďuriš, M. Koch Allotype: 1♀ CW 15.2 mm, MNHN-IU-2014-10091, [GenBank n. MZ 127803], 30 Aug. 2013, fcn UO 60 G- Vn 13, coll. Z. Ďuriš, A. Šobáňová Paratypes: 1♂ CW 18,2 mm, MNHN-IU-2014-10094, [GenBank n. MZ 127806]; 1♂ CW 23.4 mm, MNHN-IU- 2014-10097; 1♀ CW 14.3 mm, MNHN-IU-2014-10092, [GenBank n. MZ 127804]; 19♂♂ CW 14.4–21.7 mm, 2♀♀ CW 11.0, 11.5 mm, voucher n. MNHN-IU-10098, 27 Jun. 2012, fcn UO 12 Pa-Vn12, coll. Z. Ďuriš, M. Koch. Other material: 4♂♂ CW 13.2–20.7 mm; 2♀♀ CW 16.4, 18.0 mm, voucher n. MNHN-IU-10099, 26 Aug. 2013, fcn UO 46 G-Vn13, coll. Z. Ďuriš, A. Šobáňová. — 1♂ CW 20.6 mm, MNHN-IU-2014-10095, [GenBank n. MZ 127807]; 1♀ ov. CW 15.6 mm MNHN-IU-2014-10096, [GenBank n. MZ 127808]; 7♂♂ CW 12.8–23.3 mm, 3♀♀ CW 12.2–16.3 mm, voucher n. MNHN-IU-10100, 30 Aug. 2013, fcn UO 60 G-Vn13, coll. Z. Ďuriš, A. Šobáňová Comparative material. Cycloachelous orbitosinus: Syntypes, 2♂♂ CW 33.3, 33.3 mm, 2♀♀ CW 26.0, 29.2 mm, voucher n. USNM 41084, stn. B23, Mauritius, Cargados Carajos, 54.9 m, The Percy Sladen Trust Expedition, 31 Aug. 1905, H.M.S. Sealark, coll. S. J. Gardiner. Other material, 1♂ CW 23 mm, MNHN-IU-2010-6278, [GenBank n. MZ 127809], stn CP3572, Southeast off Fort Dauphin, 25°11‘ S – 47°12‘ E, 75–77 m, Atimo Vatae Expedition, 8 May 2010, fishery vessel Nosy Be 11. (Photo http://coldb.mnhn.fr/catalognumber/mnhn/iu/2010-6278).— ♂ CW 31 mm, 2♀♀ CW 19.2, 19.5 mm, MNHN-IU- 2010-3271, stn CP3576, Cap Sainte Marie, 25°43.8‘ S –45|°18.8‘ E, 47 m, Atimo Vatae Expedition, 9 May 2010, fishery vessel Nosy Be 11.— 1♂ CW 25.3 mm, 1♀ CW 26.7 mm [Fig. 2 CD], MNHN-IU-2010-3290, stn CP3547, South off Cap Sainte Andavaka, 25°17‘58.2‘‘ S – 46°40‘18.5988‘‘ E, 69–70m, Atimo Vatae Expedition, 9 May 2010, fishery vessel Nosy Be 11.— 1♂ male, CW 27.9 mm, 2♀♀ CW 20.9, 23.8 mm, 1 intersex CW 22.8, MNHN-IU- 2018-4943, stn CP3575, Cap Sainte Marie, 25°41‘19.2012‘‘ S – 45°17‘9.5964‘‘ E, 45–48 m, Atimo Vatae Expedition, 5 May 2010, fishery vessel Nosy Be 11.— 3♂♂, CW 23.4–25.5 mm, 1♀ juv. CW 18.5 mm, MNHN-IU-2010-3146, stn CP3624, Southeast off Faux-Cap, 25°38.1‘ S – 45°57.0‘ E, 63 m, Atimo Vatae Expedition, 15 May 2010, fishery vessel Nosy Be 11.— 8♂♂, CW 25.0– 29.9 mm, 3♀♀ CW 21.0– 24.4 mm, 3♀♀ ov. CW 22.1–25.2 mm, MNHN-IU- 2018-4959/B.8877, stn. 22, Southeast off Sainte Anne Island, 5°16‘ S – 55°58‘ E, 60 m, ORSTOM-Reves2 Expedition, 6 Sep.1980.— 3♂♂, CW 29.8–35.7 mm, 3♀♀ CW 19.8–28.8 mm, MNHN-IU-2018-4960/B.8878, stn. 64, Southwest off Sainte Anne Island, 4°44‘ S – 55°22‘ E, 50 m, ORSTOM-Reves2 Expedition, 20 Sep. 1980. Cycloachelous octodentatus: Holotype, 1♂ CW 21.7 mm, voucher n. NHM 1937.4.2., Siglap, Singapore, Jun. 1934, coll. Raffles Museum, det. Gordon 1938. Description of C. levigatus sp. nov. holotype. Carapace (Fig. 1B) almost hexagonal, CL/CW ratio 0.67. Front width 0.15 of CW, frontal region including inner orbital tooth 0.22 of CW, fronto-orbital width (measured between tips of outer orbital teeth) 0.57 of CW. Front subdivided into 4 teeth—median pair in length about one half of lateral; median sulcus between median teeth running ventrally to the spiniform projection not overreaching front, appressed to median epistomial tooth. Supraorbital margin smooth, with 1 well developed Y-shaped notch in middle, with tooth-like elevation near extraorbital angle. Inner orbital angle tooth-like, with glabrous ventromedial ledge. Infraorbital margin with distinct V-shaped lateral notch. Anterolateral margin armed by 9 teeth with granulated margins, first tooth larger with arched outer margin, second tooth distinctly smaller, teeth 3–8 subequal, sharp, projecting forwards, tooth 9 largest, about twice as long as penultimate, projecting laterally and forward. Posterolateral margin slightly granulate, almost straight, subequal in length with anterolateral margin; posterolateral angle rounded; posterior margin straight. Carapace with dorsal surface densely covered by very short fine pila, regions well defined, elevated, demarcated by patches of distinct knob-like granules; protogastric patches of granules separated from mesogastric; mesobranchial granules subdivided into four patches; anterolateral region with 2 indistinct submarginal granular patches separated on the level of firth anterolateral teeth; epibranchial regions poorly defined with dispersed patches of granules; both cardiac and lateral postcardiac, median postcardiac regions each with simple patch of granules; additional oval patch of granules on each side of carapace between lateral postcardiac region and posterolateral margin. All male thoracic sternites glabrous (Fig 2B); sternites 3, 4 well separated; sternite 4 with distinct median groove, sternites 7, 8 fused medially, sulcus distinct on exposed outer half. Locking mechanism postero-medially on sternite 5 on sides of pleonal cavity; pair of short, bulbous, posteriorly directed lobes reaching about one quarter of sternite 6. Pleon (Fig. 2B, 3D) ‘T’-shaped, with pleomeres 3–5 fused, with borders only very feebly demarcated by transverse shallow glabrous transversal sulci. Pleomeres 4–6 together with telson each smooth and glabrous. Sixth pleomere 0.8 times longer than wide, 1.6 times longer than telson, lateral margins rounded and forming obtuse angle. Telson narrowly triangular, 1.4 times longer than basal width, with rounded tip and slightly concave posterior margin. Pleomere 3 with high sharp convex laminar crest; lateral margins of crest only slightly concave, posterolateral angle rounded. Crest on pleomere 2 distinctly lower than on pleomere 3, posterior margin sinuate. Basal antennal segment with deep groove on the part entering orbital cavity. Third maxillipeds (Fig. 3F) gently granulate on ischium, merus, exopod, with densely pilose margins; palp tapering distally, segments subcylindrical; merus slightly longer than broad, lateral, medial parts glabrous, anterolateral angle creating triangular lateral projection; ischium about 1.55 times merus length, with distinct longitudinal glabrous groove and row of granules on lateral margin. Exopod stout, about 0.4 of ischium width, with subdistal triangular projection on medial border; flagellum longer than merus width. Other mouthparts not dissected. Chelipeds (Fig. 1B, 3E) symmetrical, relatively robust, length about 0.9 of maximum carapace width (incl. lateral teeth). Merus with 5 spines on anterior, 2 on posterior, borders, anterior one flattened. Carpus with 1 sharp inner spine, 1 flattened outer spine; one distinct carina on dorsal surface. Upper surface of palm with 2 granular crests, inner one ending by spine distally, outer surface with small spiniform tooth over articulation with carpus, with 2 granular crests ending on level of finger articulation, lower arched, creating outer ventral, sharply produced, margin; inner surface of palm with longitudinal granulate keel ending on the pollex tip and bearing very distinct sharp granules reaching half of the pollex; fingers straight, tapering distally, tips arched, 0.45 of maximum palm length, distinctly carinate. No molariform teeth present on cutting edge; fingers otherwise with some hardly defined groups tri- or tetralobed serial conical teeth. Ambulatory leg 5 with merus gently serrate on posterodistal angle. Natatorial dactylus oval, 2.25 times longer than maximum width, elliptical, with longitudinal median groove; upper surface with two longitudinal glabrous paths. Propodus with 3 longitudinal glabrous paths on upper surface—2 anterior, 1 posterior marginal. Male G1 (Fig. 4A) long, slender; proximal part robust, biconvex, distinct proximolateral lobe trapezoidal, with serrate posterior half of lateral margin; distal part arched, tapering, with apex slender, not expanded. Male paratypes. Morphologically identical with holotype, CL/CW ratio near to 0.7. Chelipeds with 5, rarely 4 or 6 anterior spiniform teeth on merus. Lateral margins of pleonal segment 6 occasionally more rounded. Allotype. Selected female reaching 15.2 mm, CL/CW ratio 0.73. Shape of the carapace is consistent with that of males. Pleon (Fig. 2E) broadly subtriangular, laterally convex, with the distinct transversal ridge on pleomere 4; pleomere 6 broadly rounded, semicircular; telson small, triangular, slightly longer than wide, with rounded tip. Chelipeds with the inner surface without roughly granulated longitudinal keel in contrast to males. Molariform teeth present on cutting edge or right chela; fingers with some hardly-defined groups tri- or tetralobed serial conical teeth. Vulvae (Fig. 2F) located in the middle of pleonal sternites 6 on sides of pleonal cavity; gonopores forming narrow indistinct fissures with medial (inner) margin slightly convex and lateral (outer) margin straight. Colouration. The general colour of the carapace and chelipeds is yellowish-brown with the red dark granules scattered evenly, defining more or less the regions of the carapace (Fig. 5B); pollex with dark red granulate ridge on its ventral side. Sternites 4–8, and ventral surface of chelipeds and ambulatory legs pink. Posterior part of pleon with two pink stripes. Swimming legs with black tips and margins. Etymology. Due to the character of the surface of sternites and pleon, the Latin word ‘ levigatus ’ (smooth) is proposed for the species name. Remarks. Ward (1942) established genus Cycloachelous based on morphological characters: (1) carapace flat almost circular in outline (2) fronto-orbital margins more than half as wide as total CW (3) orbits with significant dorsal inclination and lower orbital margins clearly visible from a dorsal view (4) anterolateral angle of the merus of the external maxillipeds strongly produced or auriculate. The actual number of representative species is for the genus is more or less unclear. Nguyen & Ng (2010) discussed the taxonomic position of the genus and its species composition where 9 taxa were chosen as its possible representatives. Two of them were separated into the new genus Cavoportunus Nguyen & Ng 2010. Actually, the genus contains 6 species (2 subspecies): C. granulatus granulatus (H. Milne-Edwards, 1834), C. granulatus unispinosus (Miers, 1884), C. elongatus (A. Milne-Edwards, 1861), C. octodentatus (Gordon, 1938), C. orbicularis (Richters, 1880), C. orbitosinus (Rathbun, 1911) and C. suborbicularis (Stephenson, 1975). Four species (two subspecies) are easily distinguishable from C. levigatus sp. nov.: C. granulatus unispinosus, with one tooth on the posterior border of the cheliped merus versus two teeth posteriorly on the cheliped merus in C. levigatus sp. nov., C. orbicularis and C. elongatus with circular shape of the carapace and with small ninth anterolateral teeth versus almost hexagonal carapace with double sized ninth anterolateral teeth in C. levigatus sp. nov. C. granulatus granulatus and C. suborbicularis with short, stout G1 with hook-like apex versus relatively slender and long in C. levigatus sp. nov. The last two species— C. octodentatus and C. orbitosinus seem to be most relative to newly presented one. Examination of the photos of holotype C. octodentatus (Fig. 6A–D) confirmed the presence of third and fourth fused anterolateral teeth and different shape of male G1, which is stouter and bent in the first distal third. This correspond well with the description and figures of Gordon (1938) and is significant for distinguishing of both species. The other morphological characters are almost identical with C. levigatus sp. nov. Cycloachelous orbitosinus is morphologically very similar C. levigatus sp. nov., but there is a set of characters to distinguish both taxa: (1) thoracic sternites with distinct sulci (Fig 2A, 3A) versus glabrous thoracic sternites (Fig. 2B, 3D); (2) the male pleon with very distinct sulci on the surface of pleomeres 3–6 and with lateral margins of the sixth pleomere convex, anteriorly convergent (Fig. 2A, 3A), versus pleon with glabrous pleomeres, except of the indistinct sulcus on pleomere 3 and with lateral margins broadly angular (Fig. 2B, 3D); (3) female pleon with very distinct sulci on the surface of pleomeres 3–6 and with lateral margins of the pleomere 5 and 6 rounded/semicircular (Fig. 2C), versus pleon with glabrous pleomeres, except of the sulcus on pleomere 3 and with lateral margins convex (Fig. 2E); (4) third maxillipeds anterolateral triangular projection forming about one half (Fig. 3B) versus one third of anterior margin (Fig. 3E); (5) chela with the spine on upper surface directed obliquely upward (Fig. 3C) versus forward direction (Fig 3F); (6) inner surface of palm with indistinct granulate keel (Fig. 1A, 7 AB), versus longitudinal granulate keel bearing very distinct sharp granules reaching half of the pollex (Fig. 1B); (7) G1 distinctly arched with ventrally directed openings (Fig. 4B), versus G1 slightly arched with opening directed forward (Fig. 4A); (8) general colour of the carapace and chelipeds red (Fig. 5A) versus yellowish-brown (Fig. 5B). The molecular data support the presence of two well separated species (Fig. 9). The actual distribution of C. levigatus sp. nov. is unclear, as previous records for C. orbitosinus might overlap with present new species. Only some of the previously published data provide details to match the presented new species by morphological (de Haan 1833; Stephenson & Rees 1967; Sakai 1939; Sakai 1976; Yamaguchi & Baba 1993) or molecular characters (Spiridonov et al. 2014). Gordon (1938: Fig 5g) and Stephenson & Rees (1967: figs. 6d, h) mentioned specimens from Philippines with long and slender G1 distinctly different in comparison with C. orbitosinus and C. levigatus sp. nov., which might indicate the presence of another closely related species. Distribution. Nhatrang Bay, Vietnam —the type locality. A previous report from the same locality: Spiridonov et al. (2014). The other confirmed localities are Philippines (Stephenson & Rees 1967) and Japan (Sakai 1939; Sakai 1976). In comparison with C. orbitosinus reported from the western Indian Ocean— Mauritius, Madagascar, Seychelles (Rathbun 1911; Gordon 1938; Crosnier 1962), Kenya, Socotra (Spiridonov 1994) Somalia (Vannini, M. & Innocenti 2000) and Persian (Arabian) Gulf, Gulf of Aden (Stephensen 1945; Apel & Spiridonov 1998; Naderloo 2017), it seems C. levigatus localities are in East or South-East Asia waters., Published as part of Koch, Milan, 2021, Cycloachelous levigatus sp. nov., a new swimming crab (Crustacea: Decapoda Portunidae) from the South China Sea, pp. 325-339 in Zootaxa 4970 (2) on pages 327-335, DOI: 10.11646/zootaxa.4970.2.6, http://zenodo.org/record/4766923, {"references":["Gordon, I. (1938) On three species of Portunidae (Decapoda, Brachyura) from the Malay Peninsula. Bulletin of the Raffles Museum, 14, 175 - 185.","Rathbun, M. J. (1911) The Percy Sladen Trust expedition to the Indian Ocean in 1905, Under the leadership of Mr. J. Stanley Gardiner. Vol. III. No. XI. Marine Brachyura. Transactions of the Linnean Society of London, Series 2, Zoology, 14 (2), 191 - 261, pls. 15 - 20.","Ward, M. (1942) Notes on the Crustacea of the Desjardins Museum, Mauritius Institute, with descriptions of new genera and species. Mauritius Institute Bulletin, 2 (2), 49 - 113.","Nguyen, T. S. & Ng, P. K. L. (2010) A new genus of the family Portunidae (Crustacea: Decapoda: Brachyura) and the identity of Portunus (Cycloachelous) yoronensis Sakai, 1974. Zootaxa, 2677 (1), 38 - 48. https: // doi. org / 10.11646 / zootaxa. 2677.1.4","Milne-Edwards, H. (1834) Histoire naturelle des Crustaces comprenant l'anatomie, la physiologie et la classification de ces animaux. Vol. 1. Librairie Encyclopedique de Roret, Paris, xxxv + 468 pp. https: // doi. org / 10.5962 / bhl. title. 39738","Milne-Edwards, A. (1861) Etudes zoologiques sur les Crustaces recents de la famille des Portuniens. Archives du Museum national d'Histoire naturelle de Paris, 10, 309 - 421. https: // doi. org / 10.5962 / bhl. title. 10629","Richters, F. (1880) Decapoda. In: Mobius, K. (Ed.), Beitrage zur Meeresfauna der Insel Mauritius und der Seychellen, Berlin, 1880, pp. 137 - 179.","Stephenson, W. (1975) Biological results of the Snellius Expedition, XXVI. The Portunidae (Decapoda- Brachyura) of the Snellius Expedition (part II). Zoologische Mededelingen, 49 (14), 173 - 209.","Haan, W. de (1833 - 1850) Crustacea. In: Siebold, P. F. von (Ed.) Fauna Japonica sive Descriptio Animalium, Quae in Itinere per Japoniam, Jussu et Auspiciis Superiorum, qui Summum in India Batava Imperium Tenent, Suscepto, Annis 1823 - 1830 Collegit, Noitis, Observationibus et Adumbrationibus Illustravit. Lugduni-Batavorum, Leiden, 243 pp. https: // doi. org / 10.5962 / bhl. title. 124951","Stephenson, W. & Rees, M. (1967) Some portunid crabs from the Pacific and Indian Oceans in the collections of the Smithsonian Institution. Proceedings of the United States National Museum, 120, 1 - 114. https: // doi. org / 10.5479 / si. 00963801.120 - 3556.1","Sakai, T. (1939) Studies on the Crabs of Japan IV. Brachygnatha, Brachyrhyncha. Vol. 3. Yokendo Co., Ltd., Tokyo, 365 - 741.","Sakai, T. (1976) Crabs of Japan and the Adjacent Seas. Kodansha, Tokyo, xxxix + 773 pp.","Yamaguchi, T, & Baba, K. (1993) Crustacean specimens collected in Japan by Ph. F. von Siebold an H. Burger and held by the National Natuurhistorisch Museum in Leiden and other museums. In: Yamaguchi, T. (Ed.), Ph. F. von Siebold and Natural History of Japan, Crustacea. The Carcinological Society of Japan, Tokyo, pp. 145 - 570.","Spiridonov, V. A., Neretina, T. V. & Schepetov, D. (2014) Morphological characterization and molecular phylogeny of Portunoidea Rafinesque, 1815 (Crustacea Brachyura): Implications for understanding evolution of swimming capacity and revision of the family-level classification. Zoologischer Anzeiger, 253, 404 - 429. https: // doi. org / 10.1016 / j. jcz. 2014.03.003","Crosnier, A. (1962) Crustaces Decapodes Portunidae. Faune de Madagascar, 16, 1 - 154. Available from: https: // decapoda. nhm. org / pdfs / 30643 / 30643. pdf (accessed 6 July 2017)","Spiridonov, V. A. (1994) The swimming crabs (Crustacea, Brachyura, Portunidae) of submerged rises and insular shelves of the Atlantic and Indian Oceans. Bottom fauna of seamounts. NAUKA - Transactions of the P. P. Shirshov Institute of Oceanology, 129, 126 - 152.","Stephensen, K. (1945) s. n. In: The Brachyura of the Iranian Gulf. Danish Scientific Investigations in Iran, Part IV. E. Munksgaard, Copenhagen, pp. 57 - 237.","Apel, M. & Spiridonov, V. A. (1998) Taxonomy and zoogeography of the portunid crabs (Crustacea: Decapoda: Brachyura: Portunidae) of the Arabian Gulf and adjacent waters. Fauna of Arabia, 17, 159 - 331","Naderloo, R. (2017) Atlas of Crabs of the Persian Gulf. Atlas of Crabs of the Persian Gulf. Springer, 443 pp. https: // doi. org / 10.1007 / 978 - 3 - 319 - 49374 - 9"]}

Neptunus (Achelous) orbitosinus. — Gordon 1938, 183, fig. 5g, Published as part of Koch, Milan, 2021, Cycloachelous levigatus sp. nov., a new swimming crab (Crustacea: Decapoda Portunidae) from the South China Sea, pp. 325-339 in Zootaxa 4970 (2) on page 327, DOI: 10.11646/zootaxa.4970.2.6, http://zenodo.org/record/4766923, {"references":["Gordon, I. (1938) On three species of Portunidae (Decapoda, Brachyura) from the Malay Peninsula. Bulletin of the Raffles Museum, 14, 175 - 185."]}

Portunus orbitosinus. — Stephenson & Campbell 1959, 113–114, figs 2L, 3L, pl. 3 (4), pl. 4(L), pl. 5 (L); Stephenson 1961, 108–109; Stephenson & Rees 1967, 31–34, figs. 6d, h (Form B); Stephenson & Rees 1968, 294; Stephenson 1972, 41; Stephenson 1975, 179; Moosa 1996, 524; Spiridonov 1999, 80–81; Yang et al. 2012, 145, figs 53a–f., Published as part of Koch, Milan, 2021, Cycloachelous levigatus sp. nov., a new swimming crab (Crustacea: Decapoda Portunidae) from the South China Sea, pp. 325-339 in Zootaxa 4970 (2) on page 327, DOI: 10.11646/zootaxa.4970.2.6, http://zenodo.org/record/4766923, {"references":["Stephenson, W. & Campbell, B. M. (1959) The Australian portunids (Crustacea: Portunidae). III. The genus Portunus. Australian Journal of Marine and Freshwater Research, 10, 84 - 124.","Stephenson, W. (1961) The Australian portunids (Crustacea: Portunidae). V. Recent collections. Australian Journal of Marine and Freshwater Research, 12, 92 - 128. https: // doi. org / 10.1071 / MF 9610092","Stephenson, W. & Rees, M. (1967) Some portunid crabs from the Pacific and Indian Oceans in the collections of the Smithsonian Institution. Proceedings of the United States National Museum, 120, 1 - 114. https: // doi. org / 10.5479 / si. 00963801.120 - 3556.1","Stephenson, W. & Rees, M. (1968) The Endeavour and Other Australian Museum Collections of Portunid Crabs (Crustacea, Decapoda, Portunidae). Records of the Australian Museum, 27 (13), 285 - 298. https: // doi. org / 10.3853 / j. 0067 - 1975.27.1968.447","Stephenson, W. (1972) An annotated check list and key to the Indo-West-Pacific swimming crabs (Crustacea: Decapoda: Portunidae). Bulletin of the Royal Society of New Zealand, 10, 1 - 64.","Stephenson, W. (1975) Biological results of the Snellius Expedition, XXVI. The Portunidae (Decapoda- Brachyura) of the Snellius Expedition (part II). Zoologische Mededelingen, 49 (14), 173 - 209.","Moosa, M. K. (1996) Crustacea Decapoda: deep-water swimming crabs from the south-west Pacific, particularly New Caledonia (Brachyura, Portunidae). In: Crosnier, A. (Ed.), Resultats des Campagnes MUSORSTOM. Vol. 15. Memoires du Museum national d'Histoire naturelle, 168, pp. 503 - 530.","Spiridonov, V. A. (1999) Results of the Rumphius Biohistorical Expedition to Ambon (1990). Part 8. Swimming crabs of Ambon (Crustacea: Decapoda: Portunidae). Zoologishe Mededelingen, Leiden, 73, 63 - 97.","Yang, S. - L., Chen, H. - L. & Dai, A. - Y. (2012) Fauna Sinica Invertebrata, Vol. 49. Crustacea Decapoda Portunidae. Science Press, Beijing, 417 pp."]}

Cycloachelous orbitosinus (Figs. 1.A, 2 ACD, 3A–C, 4B, 5A, 7AB, 8) Portunus (Achelous) orbitosinus. — Rathbun 1911, 205, pl. 15 (11); Naderloo 2017, 195, figs 20.27, 20.29, 20.30b. Neptunus (Achelous) orbitosinus. — Gordon 1938, 179–185, figs. 5a, b, f–f´´, 6c, d; Stephensen 1945, 120. Portunus orbitosinus. — Crosnier 1962, 55–57, figs. 88, 90, 91, 93; Stephenson 1967, 17; Spiridonov 1994, 138; Apel & Spiridonov 1998, 299–300, figs 110-111, 115; Vannini & Innocenti 2000, 65, fig. 21., Published as part of Koch, Milan, 2021, Cycloachelous levigatus sp. nov., a new swimming crab (Crustacea: Decapoda Portunidae) from the South China Sea, pp. 325-339 in Zootaxa 4970 (2) on page 327, DOI: 10.11646/zootaxa.4970.2.6, http://zenodo.org/record/4766923, {"references":["Rathbun, M. J. (1911) The Percy Sladen Trust expedition to the Indian Ocean in 1905, Under the leadership of Mr. J. Stanley Gardiner. Vol. III. No. XI. Marine Brachyura. Transactions of the Linnean Society of London, Series 2, Zoology, 14 (2), 191 - 261, pls. 15 - 20.","Naderloo, R. (2017) Atlas of Crabs of the Persian Gulf. Atlas of Crabs of the Persian Gulf. Springer, 443 pp. https: // doi. org / 10.1007 / 978 - 3 - 319 - 49374 - 9","Gordon, I. (1938) On three species of Portunidae (Decapoda, Brachyura) from the Malay Peninsula. Bulletin of the Raffles Museum, 14, 175 - 185.","Stephensen, K. (1945) s. n. In: The Brachyura of the Iranian Gulf. Danish Scientific Investigations in Iran, Part IV. E. Munksgaard, Copenhagen, pp. 57 - 237.","Crosnier, A. (1962) Crustaces Decapodes Portunidae. Faune de Madagascar, 16, 1 - 154. Available from: https: // decapoda. nhm. org / pdfs / 30643 / 30643. pdf (accessed 6 July 2017)","Spiridonov, V. A. (1994) The swimming crabs (Crustacea, Brachyura, Portunidae) of submerged rises and insular shelves of the Atlantic and Indian Oceans. Bottom fauna of seamounts. NAUKA - Transactions of the P. P. Shirshov Institute of Oceanology, 129, 126 - 152.","Apel, M. & Spiridonov, V. A. (1998) Taxonomy and zoogeography of the portunid crabs (Crustacea: Decapoda: Brachyura: Portunidae) of the Arabian Gulf and adjacent waters. Fauna of Arabia, 17, 159 - 331","Vannini, M. & Innocenti, G. (2000) Research on the coast of Somalia. Portunidae (Crustacea: Brachyura). Tropical Zoology, 13, 251 - 298. https: // doi. org / 10.1080 / 03946975.2000.10531136"]}

Portunus (Achelous) orbitosinus. — Davie 2002, 463; Ng et al. 2008, 151., Published as part of Koch, Milan, 2021, Cycloachelous levigatus sp. nov., a new swimming crab (Crustacea: Decapoda Portunidae) from the South China Sea, pp. 325-339 in Zootaxa 4970 (2) on page 327, DOI: 10.11646/zootaxa.4970.2.6, http://zenodo.org/record/4766923, {"references":["Davie, P. J. F. (2002) Crustacea: Malacostraca: Eucarida (Part 2: Anomura, Brachyura). In: Wells, A. & Houston, W. W. K. (Eds.), Zoological catalogue of Australia. 19.3 (B). CSIRO Publishing, Melbourne, Victoria, pp. 1 - 641.","Ng, P. K. L., Guinot, D. & Davie, P. J. F. (2008) Systema Brachyurorum: Part I. An annotated checklist of extant brachyuran crabs of the world. The Raffles Bulletin of Zoology, Supplement 17, 1 - 286. [https: // lkcnhm. nus. edu. sg / app / uploads / 2017 / 04 / s 17 rbz. pdf]"]}

Xiphonectes paralatibrachium Crosnier, 2002: MUSORSTOM 9 Expedition, Marquesas Islands, French Polynesia: holotype, male, CW 9 mm, MNHN-IU-2014-4110; paratype, female, CW 8.5 mm, MNHN-B 27955, 22 Aug. 1997, stn DW1143, 09° 20.9' S, 140° 02.7' W, Ua Pou I., depth 18–55 m; 1 female paratype, CW 10 mm, MNHN-B 27957, 28 Aug. 1997, stn DW1204, 09° 52.6' S, 139° 03.2' W, Hiva Oa I., depth 60–62 m., Published as part of Koch, Milan & Ďuriš, Zdeněk, 2019, Xiphonectes aculeatus sp. nov., a new swimming crab (Crustacea: Decapoda: Portunidae) from Madagascar, pp. 455-462 in Zootaxa 4551 (4) on page 456, DOI: 10.11646/zootaxa.4551.4.5, http://zenodo.org/record/2623091, {"references":["Crosnier, A. (2002) Portunidae (Crustacea, Decapoda, Brachyura) de Polynesie francaise, principalement des iles Marquises. Zoosystema, 24 (2), 401 - 449."]}

Xiphonectes latibrachium (Rathbun, 1906): male holotype, CW 10.8 mm, USNM 29676; vicinity of Modu Manu or Bird Island, Hawaii; Albatross Expedition, 7 Aug. 1902, St. 4158, depth 20–30 fathoms (36–55 m)., Published as part of Koch, Milan & Ďuriš, Zdeněk, 2019, Xiphonectes aculeatus sp. nov., a new swimming crab (Crustacea: Decapoda: Portunidae) from Madagascar, pp. 455-462 in Zootaxa 4551 (4) on page 456, DOI: 10.11646/zootaxa.4551.4.5, http://zenodo.org/record/2623091, {"references":["Rathbun, M. J. (1906) The Brachyura and Macrura of the Hawaiian islands. Bulletin of the Bureau of Fisheries, 23 (3), 827 - 930."]}

Xiphonectes aculeatus sp. nov. (Figs 1–3, 4C, D) Type material. Holotype: 1 female, CW 19.5 mm, MNHN-IU-2010-3218 (COI sequence GenBank MK330852), Atimo Vatae Expedition, 9 Jun. 2010, stn TA46, 24° 59.1' S, 47° 05.6' E, Pointe Evatra, Anse Itapera, south of Madagascar, depth 2–12 m. Description of holotype. Carapace (Figs 1A, 3A, 4D) anterior margin approximately triangular; posterior margin reduced, narrow, subrectangular; CL/CW ratio 0.54; frontal margin (including inner orbital angle) 0.23 CW, fronto-orbital width 0.46 CW. Front with 4 distinct obtuse triangular teeth; median pair distinctly smaller than lateral, with short, broadly V-shaped median notch; lateral frontal teeth separated from median ones, with asymmetric U-shaped notch approximately twice depth of median notch, outer margins slightly sinuate. Inner orbital tooth reduced but forming distinct obtuse angle extending anteriorly beyond first anterolateral tooth; notch undeveloped, indicated as short suture. Supraorbital margin with well-developed medial notch and one indistinct lateral notch. Infraorbital margin granular with a distinct V-shaped lateral notch and a prominent obtuse medial tooth approximately level with the frontal teeth in dorsal view. Anterolateral margin slightly convex, with 6 teeth; anterior 5 teeth projecting forward, first tooth bluntly rounded and smaller; second to fifth teeth subequal in size and gradually sharper posteriorly; sixth tooth (epibranchial) projecting laterally, spiniform, strong, about three times longer than preceding one, posterior margin straight, 2.5 times longer than anterior margin. Posterior part of carapace distinctly narrower than anterior one, posterolateral margin of carapace oblique, short, about half length of anterolateral margin; posterolateral angle forming laterally and upward-directed subacute tooth-like process; posterior margin slightly convex. Dorsal surface of carapace sparsely tomentose, with elevated but feebly demarcated regions bounded by patches of fine granules, and with 11 prominent knob-like tubercles, each in centre of main regions. Mesogastric region narrow, slightly elevated; metagastric regions well elevated, with large knob-like tubercle in centre; protogastric regions rounded, elevated, and with similar large tubercle in centres; mesobranchial regions each subdivided into 2 elevated areas, with central tubercles more obscured; anterolateral regions with two feeble elevations situated near 2 nd and 3 rd anterolateral teeth, respectively, anterior one larger; cardiac and median postcardiac regions each with distinct conical elevation; lateral postcardiac regions indistinct, obsolete; posterolateral regions elongated, elevated, without prominent tubercles. Epistome (Fig. 2A) narrow, with median triangular lobe formed by pair of appressed teeth, and with pair of deep notches on margins of efferent branchial channels more laterally; median epistomial tooth undeveloped. Narrow median septum fused anteriorly to front, continuing posteriorly and laterally into transverse posterior laminar walls of antennular cavities, and separated from epistome by deep narrow furrow comprising tubules of antennal glands laterally; laminar walls fused laterally to immovable basal antennal segment forming inner wall of orbit; basal antennal segment projecting with elongate process into orbit. Female thoracic sternites (Figs 2B, 3C) finely granulate, sternites 3 and 4 fused, with distinct sulcus laterally only; sternite 4 with shallow median groove; sternites 5–8 well defined, with broad median pleonal cavity; sternal sulci 4/5–6/7 with deep submedian incisions. Vulvae (Fig. 3C) large, located on sixth sternite laterally on walls of sterno-pleonal cavity, margins transversely subcircular, tear-like, with anterior margin straight, well defined, laterally rounded with sharp margin, medially leading into shallow groove running anteromedially towards midline of sterno-pleonal cavity. Transverse fissure on bottom of vulva leading into gonopore, latter hidden under lateral margin of vulva. Female pleon (Fig. 3B) with somites 3–5 each bearing distinct transverse crest on outer surface. Pleomere 6 broadly rounded, almost semicircular, with anterior margin concave to accommodate base of telson, about 0.4 of proximal width of segment; telson small and broadly triangular with convex base, height/base ratio about 0.75. Third maxilliped (Fig. 1B) finely granular on ischium, merus, and exopodal peduncle, with margins densely setose. Palp with dactylus and propodus tapering distally, carpus with large rounded transverse crest on outer side forming flattened, slightly concave, broad frontal field. Merus subtrapezoidal, lateral margin produced distally into subquadrate projection, latter bent outwards forming swollen distolateral crest with broad longitudinal furrow narrowing proximally, and demarcated medially by strong oblique crest; ischium about 1.4 times merus length, 1.8 times as long as wide, with shallow longitudinal sulcus. Exopod relatively stout, about half of ischium width, with subdistal triangular projection on inner medial border; flagellum longer than merus width. Right cheliped lost in holotype. Left cheliped (Figs 1A, 1C, 3A) moderately stout. Merus with 3 spines on anterior border, and one relatively small spine distally on posterior border. Carpus with 2 indistinct carinae on dorsal surface, and 1 sharp, very long dorsomedial, obliquely anteriorly erected spine far overreaching middle of dorsal margin of palm; flattened ventral margin forming outer angular projection visible from dorsal view. Upper surface of palm with 2 longitudinal crests, inner one distinct, ending distally into strong, compressed, obliquely anteriad erected spine reaching distal dorsal end of palm, outer crest defined only by row of granules and ending with small distal spine and distinct spiniform proximal tooth proximally over articulation with carpus. Outer surface with 2 granular crests ending on level of finger joint; inner surface of palm flattened, with 1 indistinct longitudinal keel. Fingers straight, tapering, 0.5 of maximum chela length, distinctly carinate; movable finger with distinct bilobed molariform tooth proximally on cutting edge; fingers otherwise with some bi- or trilobed serial conical teeth separated by series of small simple teeth. Ambulatory pereopods 2–4 relatively short, glabrous, dactyli and propodi compressed, both latter with row of dense setae along ventral margin, additional setal row dorsomedially on dactyli. Fifth pereopod (= swimming leg) with merus finely serrate on posterodistal margin, posterodistal angle acutely projecting, spiniform. Dactylus oval, broadly rounded distally. Colouration. The holotype has been preserved in ethanol for more than 6 years, but displays a dark broad Vshaped pattern (Fig. 3A, 4B) beginning just behind each orbit and extending posteriorly to meet on the cardiac region. Small dark ornamentations also appear on the mesobranchial regions, and the tips of the last anterolateral teeth bear traces of reddish orange colour. Etymology. The species name is derived from Latin word aculeus (sharp pointed process, thorn) to emphasise the spiniform projection on the meri of the swimming legs. Remarks. Xiphonectes A. Milne-Edwards, 1873, is comprised of 29 species (Ng et al. 2008; Spiridonov 2016). However, limited molecular phylogenetic analyses (e.g., Evans 2018) and significant intrageneric morphological variability suggest this genus may not be monophyletic. Nevertheless, the general morphology of X. aculeatus sp. nov. supports its placement in Xiphonectes, but it can be easily distinguished from most congeners by an elongate spine on the inner dorsal margin of the cheliped carpus, six anterolateral teeth on the carapace, and the shape of its third maxilliped carpus and merus. These morphological characteristics are also found in X. latibrachium (Rathbun, 1906) and X. paralatibrachium (Crosnier, 2002). However, X. aculeatus sp. nov. can be distinguished from these congeners by the following traits: (1) the anterolateral carapace teeth are subequal in size (Figs 1A, 3A, 4D), versus gradually decreasing posteriorly (Figs 4B, F); (2) the last anterolateral tooth is straight and directed laterally (Figs 1A, 2A, 3D), versus arched and directed forward (Figs 4B, F); (3) the posterolateral angles of the carapace are sharp, distinct, upward and laterally directed (Figs 1A, 3A, 4D), versus feebly upturned, not produced laterally (Figs 4B, F); (4) the frontal teeth are unequal (Figs 1A, 3A, 4D), versus subequal in size (Figs 4B, F); and (5) meri of the fifth ambulatory legs are with distinct spurlike posterodistal angle (Figs 3A, 4C), versus with obtuse anterodistal angle (Figs 4A, E; Crosnier 2002: figs 6A, 7A–D). The present record of X. aculeatus sp. nov. in the western Indian Ocean is notably remote from the related Pacific congeners, with X. latibrachium putatively restricted to Hawaii and X. paralatibrachium to French Polynesia (Rathbun 1906; Crosnier 2002). Xiphonectes aculeatus sp. nov., together with these related congeners, are quite rare in collections even when sampling efforts have been significant. The collection of Madagascan portunid crabs from the Atimo Vatae Expedition were also extensive, but included just a single specimen of X. aculeatus sp. nov. For X. paralatibrachium, only the three type specimens (MNHN) have been reported, and only the holotype specimen is known for X. latibrachium (USNM). Crosnier (1984) mentioned an additional specimen of X. latibrachium from the Seychelles REVES II Expedition (not examined here), but examination of his figures (Crosnier 1984: figs 2C–F) suggest that the specimen may represent a separate, undescribed species. Crosnier’s specimen is morphologically most similar to X. latibrachium, but displays clear differences in the shape of its carapace, including the frontal margin, and in the meri of its swimming legs. Morphologically, X. aculeatus sp. nov., X. latibrachium, and X. paralatibrachium appear to constitute a distinct Xiphonectes lineage or species complex. Unfortunately, given the rarity, poor condition, and age of vouchered material for these species, molecular phylogenetic analysis of the group was not possible. Nevertheless, we successfully generated a COI DNA barcode sequence from the holotype of X. aculeatus sp. nov. This data may prove critical for future analyses of this lineage and Xiphonectes more generally. Distribution. Known only from the type locality, off southern Madagascar, the western Indian Ocean. GenBank accession number. COI: MK330852.

Monomia lucida sp. nov. (FIGS. 1–3) Portunus argentatus, STePHeNSON & ReeS 1967b: 11–13 (iN PArT), fig. 2A, e. [NOT Portunus argentatus A. MilNe-EdWArdS, 1861] Monomia argentata, CHerTOPrud et al. 2012: 313 (iN PArT), Pl. 51f. [NOT Portunus argentatus A. MilNe-EdWArdS, 1861] Material examined. Holotype: ♂ CW 58.0 MM, MNHN-IU-2014-10082 [GENBANk N. MG563791], 6 SEP. 2013, FcN UO 76A-VN13.— Allotype: ♀ CW 50.5 MM, MNHN-IU-2014-10083 [GENBANk N. MG563793], 6 SEP. 2013, FcN UO 76A-VN13.— Paratypes: 1♀ CW 32.2 MM, MNHN-IU-2014-10084 AND 1♀ CW41.7 MM, MNHN-IU- 2014-10085 [GENBANk N. MG563794], FcN UO 76A-VN13.—1♀ CW 45.2 MM, NHMUK 2017.401, cOLOUR PHOtO, 30 Aug. 2013, fcn UO 60F-Vn13.—1♂ CW 42.5 mm, NHMUK 2017.402 [GenBank n. MG563792; G1 dissected FOR SEM], 27 JUL. 2012, FcN UO 12G-VN12. ALL cOLLEctED FROM CUǻ Bé FISHING PORt (12°20'6.92"N, 109°12'13.88"E), NORtH OF NHAtRANG, KHANH HOA PROVINcE, VIEtNAM, cOLL. M. KOcH, Z. ĎURIŠ. Comparative material. Monomia argentata : Indonesia. 2♂♂ CW 33.2 MM [GENBANk N. KY524474], 35.5 MM [GENBANk N. KY524473], 1♀ CW 38.0 MM [GENBANk N. KY524472], ZRC 2003.0522, StN EA-TT06, TELUk TAREMPA, ANAMbAS, 14 MAR. 2002 —1♂ CW 30.1 MM [GENBANk N. KY524476], 1♀ 36.2 MM [GENBANk N. KY524475], ZRC 2003.0523, StN EA-TT08, W. cOASt OF PULAU BUNGURARI, NAtUNA, 18 MAR. 2002. ALL cOLLEctED by EXPEDItION ANAMbAS 2002, cOLL. T. TAN et al., DEt. P.K.L. NG et al., NIGHt tRAWLS (StAtION DAtA: NG et al. 2004). Vietnam. 1♂ CW 36.7 MM, MNHN-IU-2014-10072, 9 AUG. 2010, FcN UO 29F-VN10, cOLL. Z. ĎURIŠ, I. HORká.—1♂ jUVENILE CW 20.0 MM, MNHN-IU-2014-10073, 14 AUG. 2011, cOLL. M. KOcH.—1♀OV CW 35.3 MM, MNHN-IU-2014-10074 [GENBANk N. KY524477], 14 AUG. 2012, FcN UO-110J-VN12, cOLL. M. KOcH, Z. ĎURIŠ.— 1♂ CW 32.4 MM, MNHN-IU-2014-10075 [GENBANk N. KY524479], FcN UO-12I-VN12, cOLL. M. KOcH, Z. ĎURIŠ.— 1♂ CW 36.8 MM, MNHN-IU-2014-10076 [GENBANk N. KY524480], FcN UO-12I-VN12, cOLL. M. KOcH, Z. ĎURIŠ.— 1♂ CW 27.0 MM, MNHN-IU-2014-10077, 27 JUL. 2012, FcN UO-12I-VN12, cOLL. M. KOcH, Z. ĎURIŠ.—4♂♂ CW 22.8–35.5 mm; 2♀♀ CW 23.4, 32.9 mm; 2♀♀ov, CW 26.3, 37.8 mm; 3♀♀ subadult, CW 22–23.5 mm), 27 Jul. 2012, MNHN-IU-2014-10078, fcn UO-12I-Vn12, coll. M. Koch, Z. Ďuriš.—5♂♂ CW 22.8–30.4 mm; 2♀♀ CW 26.4, 31 mm; 2♀♀ov CW 26.6, 31.2 mm, 27 Jul. 2012, fcn UO 12I-Vn12, coll. M. Koch, Z. Ďuriš.—2♂♂ CW 31.0, 31.2 MM, 2♀♀OV, CW 29.5, 31.0 MM, 24 AUG. 2013, FcN UO-25D-VN13, cOLL. Z. ĎURIŠ, A. ŠObáňOVá.—1♀ CW 36.0 MM, IOM [GENBANk N. KY524478], 6 SEP. 2013, FcN UO-76E-VN13, cOLL. Z. ĎURIŠ, A. ŠObáňOVá. ALL cOLLEctED FROM CUǻ Bé FISHING PORt (12° 20' N, 109° 12' E), NORtH OFF NHAtRANG, KHANH HOA PROVINcE. Taiwan. 1♂ CW 32.2 MM, 1♀OV CW 27.5 MM, 3♀♀ CW 34–42.1 MM, 3 SEP. 2012, UO-28F-TW12, cOLL. Z. ĎURIŠ. DONGGANG FISHING PORt, SW TAIWAN ( 24° 56' N, 121° 54' E): 1♂ CW 36.4 MM, NMMBCD4072 [GENBANk N. KY524468], 8 SEP. 2012, FcN UO-88C-TW 2012, cOLL. Z. ĎURIŠ, C.-W. LIN.—1♀♀ CW 41.9 MM NMMBCD4073 [GENBANk N. KY524467], 8 SEP. 2012, FcN UO-88C-TW 2012, cOLL. Z. ĎURIŠ, C.-W. LIN.—2♂♂ CW 35.4, 35.5 MM, 2♀♀ CW 32.6, 40.2 MM, 8 SEP. 2012, UO-88C-TW 2012, cOLL. Z. ĎURIŠ, C.-W. LIN.—1♂ CW 37.2 MM, MNHN-IU-2014-10080 [GENBANk N. KY524470], 12 SEP. 2015, FcN UO-34-TW15, cOLL. Z. ĎURIŠ, A. ŠObáňOVá, C.-W. LIN.—1♂ CW 37.9 MM, MNHN-IU-2014-10081 [GENBANk N. KY524469], 12 SEP. 2015, FcN UO-34-TW15, cOLL. Z. ĎURIŠ, A. ŠObáňOVá, C.-W. LIN.—1♀,CW 38.9 MM, MNHN-IU-2014-10079 [GENBANk N. KY524471], 12 SEP. 2015, UO-34-TW15, cOLL. Z. ĎURIŠ, A. ŠObáňOVá AND C.-W. LIN.—1♀OV CW 31.0 MM, 2♀♀ CW 31.8, 36.6 MM, 12 SEP. 2015, FcN UO-34-TW15, cOLL. Z. ĎURIŠ, A. ŠObáňOVá, C.-W. LIN. ALL cOLLEctED FROM DASI FISHING PORt, NE TAIWAN (24° 56' N, 121° 54' E. Monomia gladiator: 1♂ CW 34.5 MM, MNHN-IU-2014-10087 [GENBANk N. KY524466], 1♀ CW 32.0 MM, 27 JUL. 2012, FcN UO 12H-VN12, CUǻ Bé FISHING PORt (12°20'6.92"N, 109°12'13.88"E), NORtH OF NHAtRANG, KHANH HOA PROVINcE, Vietnam, cOLL. M. KOcH, Z. ĎURIŠ. Monomia pseudoargentata: 1♂ CW 24.1 MM, MNHN-IU-2014-10086 [GENBANk N. KY524463], 14 AUG. 2012, FcN UO 110G2-VN12, CUǻ Bé FISHING PORt (12°20'6.92"N, 109°12'13.88"E), NORtH OF NHAtRANG, KHANH HOA PROVINcE, Vietnam, cOLL. M. KOcH, Z. ĎURIŠ. Monomia samoensis: HOLOtyPE, jUVENILE ♂ CW 15.0 MM, AMNH 7482, PAGO PAGO HARbOUR, Samoa, ON SURFAcE, 6 Oct. 1936. Description of holotype. CARAPAcE (FIG. 2A) tRANSVERSALLy HEXAGONAL, CL/CW RAtIO 0.6. FRONt WIDtH 0.14 OF CW, FRONtAL REGION INcLUDING INNER ORbItAL tOOtH 0.19 OF CW, FRONtO-ORbItAL WIDtH (bEtWEEN tIPS OF OUtER ORbItAL tEEtH) 0.40 OF CW. FRONt SUbDIVIDED INtO FOUR tEEtH—MEDIAN PAIR DIStINctLy SMALLER tHAN LAtERAL; MEDIAN SULcUS bEtWEEN MEDIAN tEEtH RUNNING VENtRALLy tO SPINIFORM PROjEctION OVERREAcHING FRONt, APPRESSED tO DIStINctLy SHORtER MEDIAN EPIStOMIAL tOOtH. SUPRAORbItAL MARGIN GRANULAtED, WItH ONE WELL DEVELOPED NOtcH IN MIDDLE, WItH tOOtH-LIkE ELEVAtION NEAR EXtRAORbItAL ANGLE; LAttER WItH ADDItIONAL tOOtH VENtRALLy. INNER ORbItAL ANGLE tOOtH-LIkE, WItH GLAbROUS VENtROMEDIAL LEDGE. INFRAORbItAL MARGIN WItH SHALLOW bROAD MEDIAN NOtcH; NARROW DEEP LAtERAL NOtcH. ANtEROLAtERAL MARGIN ARMED by NINE tEEtH WItH GRANULAtED MARGINS, FIRSt tOOtH LARGER WItH SINUOUS OUtER MARGIN, tEEtH 2–8 SUbEqUAL, SHARP, PROjEctING FORWARDS, tOOtH 9 LARGESt, PROjEctING LAtERALLy. POStEROLAtERAL MARGIN SLIGHtLy GRANULAtE, cONcAVE, SHORtER tHAN ANtEROLAtERAL MARGIN; POStEROLAtERAL ANGLE ROUNDED; POStERIOR MARGIN SLIGHtLy cONVEX. CARAPAcE WItH DORSAL SURFAcE DENSELy cOVERED by SHORt PILA, REGIONS WELL DEFINED, ELEVAtED, DEMARcAtED by PAtcHES OF DIStINct kNOb-LIkE GRANULES; LEFt PROtOGAStRIc PAtcH OF GRANULES cONNEctED POStERO-MEDIALLy WItH MESOGAStRIc ONES (RIGHt ONE SEPARAtED FROM tHOSE); MESObRANcHIAL GRANULES SUbDIVIDED INtO FOUR PAtcHES; ANtEROLAtERAL REGION WItH 2 SUbMARGINAL GRANULAR PAtcHES; cARDIAc, LAtERAL POStcARDIAc, MEDIAN POStcARDIAc REGIONS EAcH WItH SIMPLE PAtcH OF GRANULES; ADDItIONAL OVAL PAtcH OF GRANULES ON EAcH SIDE OF cARAPAcE bEtWEEN LAtERAL POStcARDIAc REGION AND POStEROLAtERAL MARGIN. MALE tHORAcIc StERNItES 1–4 DIStINctLy GRANULAtE; StERNItES 3, 4 FUSED, WItHOUt DIStINct SULcUS; StERNItE 4 WItH NARROW MEDIAN GROOVE, StERNItES 7, 8 FUSED MEDIALLy, SULcUS DIStINct ON EXPOSED OUtER HALF. LOckING MEcHANISM POStERO-MEDIALLy ON StERNItE 5 ON SIDES OF PLEONAL cAVIty; PAIR OF ELONGAtE, POStERIORLy DIREctED, DIStALLy DEPRESSED LObES REAcHING MIDDLE OF StERNItE 6, bOtH APIcES WItH ANtERIORLy DIREctED VENtRAL DENtIcLE; LAttER cORRESPONDING WItH PAIR OF ANtEROLAtERAL HOLLOWS ON INNER SIDE OF PLEOMERE 6. PLEON (FIG. 2B) ‘T’-SHAPED, WItH PLEOMERES 3–5 FUSED, WItH bORDERS OF PLEOMERES DEMARcAtED by DIStINct tRANSVERSE GLAbROUS RIDGES, PLEOMERES 4, 5 EAcH WItH LONG tRANSVERSE RIDGE, DIStAL HALF OF PLEOMERE 5 AND PLEOMERE 6 WItH MEDIAN GLAbROUS RIDGE. TELSON NARROWLy tRIANGULAR, 1.5 tIMES LONGER tHAN bASAL WIDtH, WItH ROUNDED tIP, bROADLy ROUNDED POStERIOR MARGIN. SIXtH PLEOMERE 1.25 tIMES LONGER tHAN WIDE, 2.6 tIMES LONGER tHAN tELSON, LAtERAL MARGINS cONVEX, SUbPARALLEL, WItH bROADLy ROUNDED ANtEROLAtERAL ANGLES DIStINctLy REAcHING bEyOND bASE OF tELSON; PAIR OF ANtEROLAtERAL LOckING HOLLOWS ON INNER SIDE. SULcUS bEtWEEN PLEOMERES 4, 5 DIStINct, WItH PAIR OF DEEP SUbMEDIAN DEPRESSIONS; bORDER bEtWEEN PLEOMERES 4, 5 FEEbLy DEMARcAtED. POStERIOR MARGIN OF bODy (ON PLEOMERE 3) FORMING HIGH SHARP LAMINAR cRESt, INDIStINctLy SINUAtE MEDIALLy ON OUtLINE; LAtERAL MARGINS OF cRESt DEEPLy cONVEX, POStEROLAtERAL ANGLES ROUNDED. CRESt ON PLEOMERE 2 DIStINctLy LOWER tHAN ON PLEOMERE 3, POStERIOR MARGIN SINUAtE, tRIPLy cONVEX, WItH MEDIAN cONVEXIty MORE PRODUcED, LAtERAL MARGIN PRODUcED tO ELONGAtE tOOtH. BASAL ANtENNAL SEGMENt WItH ELONGAtE LAtERAL LObE WItH bLUNt APEX ENtERING ORbItAL cAVIty. THIRD MAXILLIPEDS (FIG. 2C) DIStINctLy GRANULAtE ON IScHIUM, MERUS, EXOPOD, WItH DENSELy PILOSE MARGINS; PALP tAPERING DIStALLy, SEGMENtS SUbcyLINDRIcAL; MERUS SLIGHtLy LONGER tHAN bROAD, LAtERAL, MEDIAL PARtS GLAbROUS, ANtEROLAtERAL ANGLE cREAtING tRIANGULAR PROjEctION; IScHIUM AbOUt 1.7 tIMES MERUS LENGtH, WItH LONGItUDINAL GLAbROUS GROOVE. EXOPOD StOUt, AbOUt HALF OF IScHIUM WIDtH, WItH SUbDIStAL tRIANGULAR PROjEctION ON MEDIAL bORDER; FLAGELLUM LONGER tHAN MERUS WIDtH. OtHER MOUtHPARtS NOt DISSEctED. CHELIPEDS (FIG. 2D) SyMMEtRIcAL, RELAtIVELy RObUSt, LENGtH 0.8 OF MAXIMUM cARAPAcE WIDtH (INcL. LAtERAL tEEtH). MERUS WItH 4 SPINES ON ANtERIOR, 2 ON POStERIOR, bORDERS, WItH ANtERIOR ONE DEPRESSED, WItH SERRAtE ANtERIOR MARGIN. CARPUS WItH 1 SHARP INNER SPINE, 1 FLAttENED OUtER SPINE (LAttER DOUbLE ON LEFt cHELIPED); 2 DIStINct cARINAE ON DORSAL SURFAcE. UPPER SURFAcE OF PALM WItH 2 GRANULAR cREStS, INNER ONE ENDING by SPINE DIStALLy, OUtER SURFAcE WItH SMALL SPINIFORM tOOtH OVER ARtIcULAtION WItH cARPUS, WItH 2 GRANULAR cREStS ENDING ON LEVEL OF FINGER ARtIcULAtION, LOWER ARcHED, cREAtING OUtER VENtRAL, SHARPLy PRODUcED, MARGIN; INNER SURFAcE OF PALM WItH ObtUSE LONGItUDINAL kEEL DIVIDING VENtROMEDIAL AND FLAt VENtROLAtERAL SURFAcES; SURFAcES FINELy GRANULAtE, WItH GRANULES ORDERED tO LONGItUDINAL LINES OR SHORt tRANSVERSE SqUAMIFORM ROWS; FINGERS StRAIGHt, tAPERING DIStALLy (LEFt FIXED FINGER WItH bROkEN tIP IN HOLOtyPE), 0.7 OF MAXIMUM PALM LENGtH, DIStINctLy cARINAtE. RIGHt MOVAbLE FINGER WItH MOLARIFORM tOOtH PROXIMALLy ON cUttING EDGE; FINGERS OtHERWISE WItH SOME tRI- OR tEtRALObED SERIAL cONIcAL tEEtH. AMbULAtORy LEG 5 WItH MERUS SERRAtE ON bOtH ANtERO- AND POStERODIStAL ANGLES. NAtAtORIAL DActyLUS OVAL, 2.2 tIMES LONGER tHAN MAXIMUM WIDtH, bROADLy ROUNDED DIStALLy, WItH LONGItUDINAL MEDIAN GROOVE, WItH WELL-DEFINED ROUNDED DARk SPOt DIStALLy; UPPER SURFAcE FINELy PILOSE, WItH 5 LONGItUDINAL GLAbROUS PAtHS—PAIRED SUbMEDIAN, MARGINAL, AND ADDItIONAL ONE cLOSE tO POStERIOR MARGINAL PAtH. PROPODUS WItH 4 LONGItUDINAL GLAbROUS PAtHS ON UPPER SURFAcE—3 ANtERIOR, 1 POStERIOR MARGINAL. MALE G1 (FIG. 3 AB) LONG, SLENDER; PROXIMAL PARt RObUSt, tAPERING DIStALLy, PROXIMOLAtERAL LObE SUbqUADRAtE, WItH POINtED ANtERIOR ANGLE; G1WItH REctANGULAR cURVAtURE IN AbOUt 2/3 OF LENGtH, DIStAL PARt ALMOSt UNIFORMLy SLENDER; APEX SLENDER, NOt EXPANDED, WItH ObLIqUE DIStOVENtRAL OPENING, SUbtRIANGULAR tIP. Male paratype. MORPHOLOGIcALLy cONSIStENt WItH HOLOtyPE, SMALLER, CL/CW RAtIO 0.55. RIGHt cHELIPED WItH 5 ANtERIOR SPINIFORM tEEtH ON MERUS. Female paratypes. FEMALES OF SMALLER SIzE tHAN HOLOtyPE MALE, CL/CW RAtIO 0.58, 0.56, 0.58 FOR FEMALES ORDERED by INcREASING SIzE, RESPEctIVELy. SHAPE IS cONSIStENt WItH tHAt OF MALES, EXcEPt SEcONDARy SEXUAL cHARActERS. PLEON tRIANGULAR WItH ALMOSt StRAIGHt SIDES IN tWO SMALLER FEMALES. PLEON OF LARGESt FEMALE bROADLy tRIANGULAR, LAtERALLy cONVEX, WItH DIStINct tRANSVERSAL RIDGE ON EAcH PLEOMERE 4, 5; PLEOMERE 6 bROADLy ROUNDED, ALMOSt SEMIcIRcULAR; tELSON SMALL, SLIGHtLy LONGER tHAN WIDE, WItH ROUNDED tIP. VULVAE (FIG. 3D) LOcAtED ON StERNAL SUtURES 5/6 ON SIDES OF PLEONAL cAVIty; MEDIAL (INNER) SIDE OF OVAL MARGIN INDIStINct, LAtERAL (OUtER) MARGIN DEFINED by PAIR OF cLOSELy SEt DIStINct ROUNDED tUbERcLES SUbDIVIDED by RESPEctIVE StERNAL SUtURE, tUbERcLES MEDIALLy OVERHANGING LAtERALLy DIREctED GONOPORE ON bOttOM OF VULVA. Colouration. THE GENERAL cOLOUR OF tHE cARAPAcE AND cHELIPEDS IS yELLOWISH bROWN WItH RED AND WHItE PAtcHES OF GRANULES, WHIcH IS ALSO VISIbLE ON FRESHLy PRESERVED SPEcIMENS (FIG. 1). SEGMENtS AND DActyLI OF tHE AMbULAtORy LEGS, INcLUDING cHELIPEDS, ARE PURPLE. THERE IS A RELAtIVELy SMALL bUt WELL-DEFINED ROUNDED DARk PURPLE SPOt WItH A WHItE OUtLINE ON tHE DIStAL END OF tHE DActyLUS OF tHE SWIMMING LEG. OUtER RIDGES OF tHE cHELIPEDS PALM, OUtER cARPAL tOOtH, AND PLEONAL cREStS ARE DIStINctLy IRIDEScENt. Etymology. DUE tO tHE VERy StRIkING IRIDEScENcE OF VARIOUS bODy PARtS IN DAyLIGHt, tHE LAtIN WORD ‘ lucidus ’ (SHINy) IS PROPOSED FOR tHE SPEcIES NAME. Remarks. SWIMMING cRAbS OF tHE GENUS Monomia GIStEL, 1848 ARE cHARActERISED by MODERAtELy bROAD ANtEROLAtERAL tEEtH, LARGE ORbItS ON tHE cARAPAcE, tHE bASAL ANtENNAL SEGMENt WItH A bLUNt LObIFORM LAtERAL PROcESS ENtERING tHE ORbIt, A SLIGHtLy PRODUcED EPIStOME, AND tHE DIStINct ANtEROLAtERAL ANGLE OF tHE MERUS OF tHE tHIRD MAXILLIPED (ALcOck 1899). THE GENUS Monomia cURRENtLy cONtAINS 12 SPEcIES (NG et al. 2008; KOcH et al. 2015) DIStRIbUtED IN tHE INDO-WESt PAcIFIc AREA. SEVEN OF tHOSE SPEcIES ARE EASILy DIStINGUISHAbLE FROM M. lucida sp. nov.: M. rubromarginata (LANcHEStER, 1900), M. lecromi (MOOSA, 1996), AND M. calla KOcH, NGUyEN & ĎURIŠ, 2015, IN HAVING ONLy ONE tOOtH ON tHE POStERIOR bORDER OF tHE cHELIPED MERUS (LANcHEStER 1900; MOOSA 1996; KOcH et al. 2015), versus tWO tEEtH POStERIORLy ON tHE cHELIPED MERUS IN M. lucida sp. nov. Monomia petrea (ALcOck, 1899) POSSESSES A VERy LONG tOOtH ON tHE INNER SURFAcE OF tHE cHELIPED cARPUS, WHILE It IS SHORt IN M. lucida sp. nov. FOR M. euglypha (LAURIE, 1906), tHE SUbHEXAGONAL SHAPE OF ItS cARAPAcE WItH tHE DIStOLAtERAL MARGIN SINUAtE DUE tO A DIStINctLy bROADENED, POStERIORLy EXPANDED bASE OF tHE MOSt POStERIOR LAtERAL tOOtH, AND StRAIGHt, StOUt G1, ARE cHARActERIStIc (versus WItH AN ANtERIORLy SUbcIRcULAR cARAPAcE WItH A DEEPLy INcISED POStEROLAtERAL MARGINS DUE tO tHE cARAPAcE bEING StRONGLy NARROWED POStERIORLy tO tHE LEVEL OF tHE LAtERAL SPINES, AND StRONGLy cURVED AND SLENDER G1, IN M. lucida sp. nov.). Monomia curvipenis (StEPHENSON, 1961), AND M. australiensis (StEPHENSON & COOk, 1973) MAy ALSO bE DIStINGUISHED FROM tHE NEW SPEcIES by tHE SHAPE OF tHE G1; FURtHERMORE, tHE DIStAL PARt OF tHE MALE PLEON WItH tHE tELSON IS SHARPLy tRIANGULAR IN tHE tWO LAttER SPEcIES (versus PLEOMERE 6 WItH LAtERAL MARGINS cONVEX, SUbPARALLEL, WItH bROADLy ROUNDED DIStOLAtERAL ANGLES IN M. lucida sp. nov.). BASED ON PHOtOGRAPHS OF tHE tyPE SPEcIMENS OF Portunus ponticus FAbRIcIUS, 1798 (JENSEN 2006), ItS AFFILIAtION tO tHE GENUS Monomia (E.G. NG et al. 2008) MAy NEED tO bE REVISED. THE REMAINING FOUR SPEcIES, M. argentata, M. gladiator (FAbRIcIUS, 1798), M. pseudoargentata (StEPHENSON, 1961), AND M. samoensis (WARD, 1939), SEEM tO bE cLOSELy RELAtED tO M. lucida sp. nov. THE G1 OF M. pseudoargentata AND M. gladiator ARE ALSO SLENDER bUt LONGER, LESS cURVED, AND tHE cUtIcLE OF tHEIR bODy LAckS tHE IRIDEScENcE tyPIcAL FOR M. lucida sp. nov., AND M. argentata (SEE DAI & YANG 1991). A SUItE OF cHARActERS DIStINGUISHES M. argentata FROM M. lucida sp. nov.: (1) SHARP SPINIFORM ANtEROLAtERAL tEEtH OF tHE cARAPAcE (KOcH et al. 2017: FIG. 7A), versus bEING StOUt AND FORWARD DIREctED IN tHE NEW SPEcIES (FIGS 1, 2A); (2) tHE MALE PLEON WItH LAtERAL MARGINS OF tHE SIXtH PLEOMERE cONVEX, ANtERIORLy cONVERGENt (KOcH et al. 2017: FIG. 7B), versus SUbPARALLEL MARGINS WItH ROUNDED DIStAL SHOULDERS MEEtING tHE MUcH NARROWER tELSON (FIG. 2B); (3) FEMALE PLEON WItH A SHORt, GLAbROUS tRANSVERSE RIDGE ON PLEOMERE 4 ONLy (KOcH et al. 2017: FIG. 8E), versus A LONG tRANSVERSE RIDGE ON bOtH PLEOMERES 4 AND 5 (FIG. 3C); (4) RELAtIVELy NARROW cHELA, A LONG DIStODORSAL SPINE ON tHE cARPUS (KOcH et al. 2017: FIG. 7D), versus RELAtIVELy StOUt cHELA AND A REDUcED SPINE (FIG. 2D); (5) StOUt G1 WItH A bLUNt APEX (KOcH et al. 2017: FIG. 4), versus LONG, SLENDER, REctANGULAR cURVED G1 WItH A NON-EXPANDED APEX (FIG. 3A); (6) A DARk SPOt WItH DIFFUSED MARGIN ON tHE SWIMMING DActyLUS (KOcH et al. 2017: FIG. 5), versus A WELL- DEFINED, ROUNDED, WHItE OUtLINED DARk SPOt IN tHE NEW SPEcIES (FIG. 1). THE ActUAL RANGE OF M. lucida sp. nov. IS UNcLEAR, AS PREVIOUS REPORtS OF M. argentata MIGHt ALSO cOVER tHE PRESENt NEW SPEcIES. ONLy SOME OF tHE PREVIOUS DEScRIPtIONS PROVIDE DEtAILS ON tHE SHAPE OF tHE MALE PLEON AND GONOPODS (BARNARD 1950; EDMONDSON 1954; CROSNIER 1962; StEPHENSON & REES 1967A, b), OR tHE cOLOUR PAttERN (CHERtOPRUD et al. 2012), ALLOWING tHEM tO bE cOMPARED WItH tHE PRESENt NEW SPEcIES. StEPHENSON & REES (1967b: FIG 2A, E) ILLUStRAtED tHE G1 OF ‘ M. argentata ’ FROM WEStERN INDIA, AND CHERtOPRUD et al. (2012) REPORtED ON LARGER bODIED SPEcIMENS OF ‘ M. argentata ’ FROM VIEtNAM (UP tO CW 46 MM), AND PROVIDED A cOLOUR PHOtOGRAPH (CHERtOPRUD et al. 2012: PL. 51F), WHIcH ALL cLEARLy IDENtIFy At LEASt SOME tHEIR SPEcIMENS AS bELONGING tO tHE PRESENt NEW SPEcIES. THUS, FOR NOW tHE kNOWN RANGE OF M. lucida sp. nov. IS LIMItED tO VIEtNAM (SOUtH CHINA SEA) AND NORtH-WEStERN INDIA (ARAbIAN SEA). THE SyStEMAtIc StAtUS OF ANOtHER SPEcIES, M. samoensis (WARD, 1939), IS UNcLEAR AS It WAS DEScRIbED FROM A SINGLE SMALL jUVENILE MALE (FIG. 5) FROM SAMOA. OUR RE-EXAMINAtION OF tHE HOLOtyPE (AMNH 7482; 8.5 X 15 MM OF tHE cARAPAcE SIzE) HAS REVEALED tHAt tHE PLEON OF M. samoensis IS SUbtRIANGULAR, tAPERING DIStALLy. THE SPEcIMEN HAS UNDEVELOPED GONOPODS, bUt tHE FUSED PLEOMERES 3–5 cONFIRM It IS A MALE. THE DIStRIbUtION OF PAtcHES OF GRANULES DORSALLy ON tHE cARAPAcE DIFFERS FROM tHAt DEScRIbED HERE FOR M. lucida sp. nov., AND tHE ANtEROLAtERAL MARGIN IS PROPORtIONALLy DIStINctLy LONGER. THE DARk SPOt ON tHE LASt SEGMENt OF tHE SWIMMING LEG IS LARGE AND NOt cIRcULAR, AS IS ALSO EVIDENt FROM tHE ORIGINAL PHOtOGRAPHS OF M. samoensis PROVIDED by WARD (1939: FIGS. 5, 6). THE EXtERNAL MORPHOLOGy OF tHE PRESERVED HOLOtyPE ARE SHOWN AGAIN HERE (FIG. 7A, B). ItS SPEcIFIc StAtUS MIGHt bE REVISED IN tHE FUtURE bASED ON FRESHLy cOLLEctED tOPOtyPIc SPEcIMENS. ALcOck (1899) MENtIONED A VARIEty ‘ Neptunus argentatus VAR. glareosus ’ FROM tHE ANDAMAN ISLANDS tHAt MIGHt ALSO bELONG tO tHE M. argentata SPEcIES cOMPLEX. AccORDING tO tHE DEScRIPtION by ALcOck (1899), SPEcIMENS OF tHIS tAXON ARE cOMPLEtELy WItHOUt tOMENtUM ON tHEIR cARAPAcE, WHILE tHE cARAPAcE DORSUM AND PLEON OF M. argentata, s. str., AND M. lucida sp. nov., ARE DENSELy cOVERED by FINE PILA. THE FORMER SPEcIMENS ALSO POSSESS A HIGH tHIN cRESt ON PLEONAL SEGMENt 3, REPORtED AS bEING “tWIcE AS PROMINENt AS IS IN tHE tyPIcAL FORM” (ALcOck

Monomia lucida sp. nov. (FIGS. 1���3) Portunus argentatus, STePHeNSON & ReeS 1967b: 11���13 (iN PArT), fig. 2A, e. [NOT Portunus argentatus A. MilNe-EdWArdS, 1861] Monomia argentata, CHerTOPrud et al. 2012: 313 (iN PArT), Pl. 51f. [NOT Portunus argentatus A. MilNe-EdWArdS, 1861] Material examined. Holotype: ♂ CW 58.0 MM, MNHN-IU-2014-10082 [GENBANk N. MG563791], 6 SEP. 2013, FcN UO 76A-VN13.��� Allotype: ♀ CW 50.5 MM, MNHN-IU-2014-10083 [GENBANk N. MG563793], 6 SEP. 2013, FcN UO 76A-VN13.��� Paratypes: 1♀ CW 32.2 MM, MNHN-IU-2014-10084 AND 1♀ CW41.7 MM, MNHN-IU- 2014-10085 [GENBANk N. MG563794], FcN UO 76A-VN13.���1♀ CW 45.2 MM, NHMUK 2017.401, cOLOUR PHOtO, 30 Aug. 2013, fcn UO 60F-Vn13.���1♂ CW 42.5 mm, NHMUK 2017.402 [GenBank n. MG563792; G1 dissected FOR SEM], 27 JUL. 2012, FcN UO 12G-VN12. ALL cOLLEctED FROM CU�� B�� FISHING PORt (12��20'6.92"N, 109��12'13.88"E), NORtH OF NHAtRANG, KHANH HOA PROVINcE, VIEtNAM, cOLL. M. KOcH, Z. ĎURI��. Comparative material. Monomia argentata : Indonesia. 2♂♂ CW 33.2 MM [GENBANk N. KY524474], 35.5 MM [GENBANk N. KY524473], 1♀ CW 38.0 MM [GENBANk N. KY524472], ZRC 2003.0522, StN EA-TT06, TELUk TAREMPA, ANAMbAS, 14 MAR. 2002 ���1♂ CW 30.1 MM [GENBANk N. KY524476], 1♀ 36.2 MM [GENBANk N. KY524475], ZRC 2003.0523, StN EA-TT08, W. cOASt OF PULAU BUNGURARI, NAtUNA, 18 MAR. 2002. ALL cOLLEctED by EXPEDItION ANAMbAS 2002, cOLL. T. TAN et al., DEt. P.K.L. NG et al., NIGHt tRAWLS (StAtION DAtA: NG et al. 2004). Vietnam. 1♂ CW 36.7 MM, MNHN-IU-2014-10072, 9 AUG. 2010, FcN UO 29F-VN10, cOLL. Z. ĎURI��, I. HORk��.���1♂ jUVENILE CW 20.0 MM, MNHN-IU-2014-10073, 14 AUG. 2011, cOLL. M. KOcH.���1♀OV CW 35.3 MM, MNHN-IU-2014-10074 [GENBANk N. KY524477], 14 AUG. 2012, FcN UO-110J-VN12, cOLL. M. KOcH, Z. ĎURI��.��� 1♂ CW 32.4 MM, MNHN-IU-2014-10075 [GENBANk N. KY524479], FcN UO-12I-VN12, cOLL. M. KOcH, Z. ĎURI��.��� 1♂ CW 36.8 MM, MNHN-IU-2014-10076 [GENBANk N. KY524480], FcN UO-12I-VN12, cOLL. M. KOcH, Z. ĎURI��.��� 1♂ CW 27.0 MM, MNHN-IU-2014-10077, 27 JUL. 2012, FcN UO-12I-VN12, cOLL. M. KOcH, Z. ĎURI��.���4♂♂ CW 22.8���35.5 mm; 2♀♀ CW 23.4, 32.9 mm; 2♀♀ov, CW 26.3, 37.8 mm; 3♀♀ subadult, CW 22���23.5 mm), 27 Jul. 2012, MNHN-IU-2014-10078, fcn UO-12I-Vn12, coll. M. Koch, Z. Ďuri��.���5♂♂ CW 22.8���30.4 mm; 2♀♀ CW 26.4, 31 mm; 2♀♀ov CW 26.6, 31.2 mm, 27 Jul. 2012, fcn UO 12I-Vn12, coll. M. Koch, Z. Ďuri��.���2♂♂ CW 31.0, 31.2 MM, 2♀♀OV, CW 29.5, 31.0 MM, 24 AUG. 2013, FcN UO-25D-VN13, cOLL. Z. ĎURI��, A. ��Ob��ňOV��.���1♀ CW 36.0 MM, IOM [GENBANk N. KY524478], 6 SEP. 2013, FcN UO-76E-VN13, cOLL. Z. ĎURI��, A. ��Ob��ňOV��. ALL cOLLEctED FROM CU�� B�� FISHING PORt (12�� 20' N, 109�� 12' E), NORtH OFF NHAtRANG, KHANH HOA PROVINcE. Taiwan. 1♂ CW 32.2 MM, 1♀OV CW 27.5 MM, 3♀♀ CW 34���42.1 MM, 3 SEP. 2012, UO-28F-TW12, cOLL. Z. ĎURI��. DONGGANG FISHING PORt, SW TAIWAN ( 24�� 56' N, 121�� 54' E): 1♂ CW 36.4 MM, NMMBCD4072 [GENBANk N. KY524468], 8 SEP. 2012, FcN UO-88C-TW 2012, cOLL. Z. ĎURI��, C.-W. LIN.���1♀♀ CW 41.9 MM NMMBCD4073 [GENBANk N. KY524467], 8 SEP. 2012, FcN UO-88C-TW 2012, cOLL. Z. ĎURI��, C.-W. LIN.���2♂♂ CW 35.4, 35.5 MM, 2♀♀ CW 32.6, 40.2 MM, 8 SEP. 2012, UO-88C-TW 2012, cOLL. Z. ĎURI��, C.-W. LIN.���1♂ CW 37.2 MM, MNHN-IU-2014-10080 [GENBANk N. KY524470], 12 SEP. 2015, FcN UO-34-TW15, cOLL. Z. ĎURI��, A. ��Ob��ňOV��, C.-W. LIN.���1♂ CW 37.9 MM, MNHN-IU-2014-10081 [GENBANk N. KY524469], 12 SEP. 2015, FcN UO-34-TW15, cOLL. Z. ĎURI��, A. ��Ob��ňOV��, C.-W. LIN.���1♀,CW 38.9 MM, MNHN-IU-2014-10079 [GENBANk N. KY524471], 12 SEP. 2015, UO-34-TW15, cOLL. Z. ĎURI��, A. ��Ob��ňOV�� AND C.-W. LIN.���1♀OV CW 31.0 MM, 2♀♀ CW 31.8, 36.6 MM, 12 SEP. 2015, FcN UO-34-TW15, cOLL. Z. ĎURI��, A. ��Ob��ňOV��, C.-W. LIN. ALL cOLLEctED FROM DASI FISHING PORt, NE TAIWAN (24�� 56' N, 121�� 54' E. Monomia gladiator: 1♂ CW 34.5 MM, MNHN-IU-2014-10087 [GENBANk N. KY524466], 1♀ CW 32.0 MM, 27 JUL. 2012, FcN UO 12H-VN12, CU�� B�� FISHING PORt (12��20'6.92"N, 109��12'13.88"E), NORtH OF NHAtRANG, KHANH HOA PROVINcE, Vietnam, cOLL. M. KOcH, Z. ĎURI��. Monomia pseudoargentata: 1♂ CW 24.1 MM, MNHN-IU-2014-10086 [GENBANk N. KY524463], 14 AUG. 2012, FcN UO 110G2-VN12, CU�� B�� FISHING PORt (12��20'6.92"N, 109��12'13.88"E), NORtH OF NHAtRANG, KHANH HOA PROVINcE, Vietnam, cOLL. M. KOcH, Z. ĎURI��. Monomia samoensis: HOLOtyPE, jUVENILE ♂ CW 15.0 MM, AMNH 7482, PAGO PAGO HARbOUR, Samoa, ON SURFAcE, 6 Oct. 1936. Description of holotype. CARAPAcE (FIG. 2A) tRANSVERSALLy HEXAGONAL, CL/CW RAtIO 0.6. FRONt WIDtH 0.14 OF CW, FRONtAL REGION INcLUDING INNER ORbItAL tOOtH 0.19 OF CW, FRONtO-ORbItAL WIDtH (bEtWEEN tIPS OF OUtER ORbItAL tEEtH) 0.40 OF CW. FRONt SUbDIVIDED INtO FOUR tEEtH���MEDIAN PAIR DIStINctLy SMALLER tHAN LAtERAL; MEDIAN SULcUS bEtWEEN MEDIAN tEEtH RUNNING VENtRALLy tO SPINIFORM PROjEctION OVERREAcHING FRONt, APPRESSED tO DIStINctLy SHORtER MEDIAN EPIStOMIAL tOOtH. SUPRAORbItAL MARGIN GRANULAtED, WItH ONE WELL DEVELOPED NOtcH IN MIDDLE, WItH tOOtH-LIkE ELEVAtION NEAR EXtRAORbItAL ANGLE; LAttER WItH ADDItIONAL tOOtH VENtRALLy. INNER ORbItAL ANGLE tOOtH-LIkE, WItH GLAbROUS VENtROMEDIAL LEDGE. INFRAORbItAL MARGIN WItH SHALLOW bROAD MEDIAN NOtcH; NARROW DEEP LAtERAL NOtcH. ANtEROLAtERAL MARGIN ARMED by NINE tEEtH WItH GRANULAtED MARGINS, FIRSt tOOtH LARGER WItH SINUOUS OUtER MARGIN, tEEtH 2���8 SUbEqUAL, SHARP, PROjEctING FORWARDS, tOOtH 9 LARGESt, PROjEctING LAtERALLy. POStEROLAtERAL MARGIN SLIGHtLy GRANULAtE, cONcAVE, SHORtER tHAN ANtEROLAtERAL MARGIN; POStEROLAtERAL ANGLE ROUNDED; POStERIOR MARGIN SLIGHtLy cONVEX. CARAPAcE WItH DORSAL SURFAcE DENSELy cOVERED by SHORt PILA, REGIONS WELL DEFINED, ELEVAtED, DEMARcAtED by PAtcHES OF DIStINct kNOb-LIkE GRANULES; LEFt PROtOGAStRIc PAtcH OF GRANULES cONNEctED POStERO-MEDIALLy WItH MESOGAStRIc ONES (RIGHt ONE SEPARAtED FROM tHOSE); MESObRANcHIAL GRANULES SUbDIVIDED INtO FOUR PAtcHES; ANtEROLAtERAL REGION WItH 2 SUbMARGINAL GRANULAR PAtcHES; cARDIAc, LAtERAL POStcARDIAc, MEDIAN POStcARDIAc REGIONS EAcH WItH SIMPLE PAtcH OF GRANULES; ADDItIONAL OVAL PAtcH OF GRANULES ON EAcH SIDE OF cARAPAcE bEtWEEN LAtERAL POStcARDIAc REGION AND POStEROLAtERAL MARGIN. MALE tHORAcIc StERNItES 1���4 DIStINctLy GRANULAtE; StERNItES 3, 4 FUSED, WItHOUt DIStINct SULcUS; StERNItE 4 WItH NARROW MEDIAN GROOVE, StERNItES 7, 8 FUSED MEDIALLy, SULcUS DIStINct ON EXPOSED OUtER HALF. LOckING MEcHANISM POStERO-MEDIALLy ON StERNItE 5 ON SIDES OF PLEONAL cAVIty; PAIR OF ELONGAtE, POStERIORLy DIREctED, DIStALLy DEPRESSED LObES REAcHING MIDDLE OF StERNItE 6, bOtH APIcES WItH ANtERIORLy DIREctED VENtRAL DENtIcLE; LAttER cORRESPONDING WItH PAIR OF ANtEROLAtERAL HOLLOWS ON INNER SIDE OF PLEOMERE 6. PLEON (FIG. 2B) ���T���-SHAPED, WItH PLEOMERES 3���5 FUSED, WItH bORDERS OF PLEOMERES DEMARcAtED by DIStINct tRANSVERSE GLAbROUS RIDGES, PLEOMERES 4, 5 EAcH WItH LONG tRANSVERSE RIDGE, DIStAL HALF OF PLEOMERE 5 AND PLEOMERE 6 WItH MEDIAN GLAbROUS RIDGE. TELSON NARROWLy tRIANGULAR, 1.5 tIMES LONGER tHAN bASAL WIDtH, WItH ROUNDED tIP, bROADLy ROUNDED POStERIOR MARGIN. SIXtH PLEOMERE 1.25 tIMES LONGER tHAN WIDE, 2.6 tIMES LONGER tHAN tELSON, LAtERAL MARGINS cONVEX, SUbPARALLEL, WItH bROADLy ROUNDED ANtEROLAtERAL ANGLES DIStINctLy REAcHING bEyOND bASE OF tELSON; PAIR OF ANtEROLAtERAL LOckING HOLLOWS ON INNER SIDE. SULcUS bEtWEEN PLEOMERES 4, 5 DIStINct, WItH PAIR OF DEEP SUbMEDIAN DEPRESSIONS; bORDER bEtWEEN PLEOMERES 4, 5 FEEbLy DEMARcAtED. POStERIOR MARGIN OF bODy (ON PLEOMERE 3) FORMING HIGH SHARP LAMINAR cRESt, INDIStINctLy SINUAtE MEDIALLy ON OUtLINE; LAtERAL MARGINS OF cRESt DEEPLy cONVEX, POStEROLAtERAL ANGLES ROUNDED. CRESt ON PLEOMERE 2 DIStINctLy LOWER tHAN ON PLEOMERE 3, POStERIOR MARGIN SINUAtE, tRIPLy cONVEX, WItH MEDIAN cONVEXIty MORE PRODUcED, LAtERAL MARGIN PRODUcED tO ELONGAtE tOOtH. BASAL ANtENNAL SEGMENt WItH ELONGAtE LAtERAL LObE WItH bLUNt APEX ENtERING ORbItAL cAVIty. THIRD MAXILLIPEDS (FIG. 2C) DIStINctLy GRANULAtE ON IScHIUM, MERUS, EXOPOD, WItH DENSELy PILOSE MARGINS; PALP tAPERING DIStALLy, SEGMENtS SUbcyLINDRIcAL; MERUS SLIGHtLy LONGER tHAN bROAD, LAtERAL, MEDIAL PARtS GLAbROUS, ANtEROLAtERAL ANGLE cREAtING tRIANGULAR PROjEctION; IScHIUM AbOUt 1.7 tIMES MERUS LENGtH, WItH LONGItUDINAL GLAbROUS GROOVE. EXOPOD StOUt, AbOUt HALF OF IScHIUM WIDtH, WItH SUbDIStAL tRIANGULAR PROjEctION ON MEDIAL bORDER; FLAGELLUM LONGER tHAN MERUS WIDtH. OtHER MOUtHPARtS NOt DISSEctED. CHELIPEDS (FIG. 2D) SyMMEtRIcAL, RELAtIVELy RObUSt, LENGtH 0.8 OF MAXIMUM cARAPAcE WIDtH (INcL. LAtERAL tEEtH). MERUS WItH 4 SPINES ON ANtERIOR, 2 ON POStERIOR, bORDERS, WItH ANtERIOR ONE DEPRESSED, WItH SERRAtE ANtERIOR MARGIN. CARPUS WItH 1 SHARP INNER SPINE, 1 FLAttENED OUtER SPINE (LAttER DOUbLE ON LEFt cHELIPED); 2 DIStINct cARINAE ON DORSAL SURFAcE. UPPER SURFAcE OF PALM WItH 2 GRANULAR cREStS, INNER ONE ENDING by SPINE DIStALLy, OUtER SURFAcE WItH SMALL SPINIFORM tOOtH OVER ARtIcULAtION WItH cARPUS, WItH 2 GRANULAR cREStS ENDING ON LEVEL OF FINGER ARtIcULAtION, LOWER ARcHED, cREAtING OUtER VENtRAL, SHARPLy PRODUcED, MARGIN; INNER SURFAcE OF PALM WItH ObtUSE LONGItUDINAL kEEL DIVIDING VENtROMEDIAL AND FLAt VENtROLAtERAL SURFAcES; SURFAcES FINELy GRANULAtE, WItH GRANULES ORDERED tO LONGItUDINAL LINES OR SHORt tRANSVERSE SqUAMIFORM ROWS; FINGERS StRAIGHt, tAPERING DIStALLy (LEFt FIXED FINGER WItH bROkEN tIP IN HOLOtyPE), 0.7 OF MAXIMUM PALM LENGtH, DIStINctLy cARINAtE. RIGHt MOVAbLE FINGER WItH MOLARIFORM tOOtH PROXIMALLy ON cUttING EDGE; FINGERS OtHERWISE WItH SOME tRI- OR tEtRALObED SERIAL cONIcAL tEEtH. AMbULAtORy LEG 5 WItH MERUS SERRAtE ON bOtH ANtERO- AND POStERODIStAL ANGLES. NAtAtORIAL DActyLUS OVAL, 2.2 tIMES LONGER tHAN MAXIMUM WIDtH, bROADLy ROUNDED DIStALLy, WItH LONGItUDINAL MEDIAN GROOVE, WItH WELL-DEFINED ROUNDED DARk SPOt DIStALLy; UPPER SURFAcE FINELy PILOSE, WItH 5 LONGItUDINAL GLAbROUS PAtHS���PAIRED SUbMEDIAN, MARGINAL, AND ADDItIONAL ONE cLOSE tO POStERIOR MARGINAL PAtH. PROPODUS WItH 4 LONGItUDINAL GLAbROUS PAtHS ON UPPER SURFAcE���3 ANtERIOR, 1 POStERIOR MARGINAL. MALE G1 (FIG. 3 AB) LONG, SLENDER; PROXIMAL PARt RObUSt, tAPERING DIStALLy, PROXIMOLAtERAL LObE SUbqUADRAtE, WItH POINtED ANtERIOR ANGLE; G1WItH REctANGULAR cURVAtURE IN AbOUt 2/3 OF LENGtH, DIStAL PARt ALMOSt UNIFORMLy SLENDER; APEX SLENDER, NOt EXPANDED, WItH ObLIqUE DIStOVENtRAL OPENING, SUbtRIANGULAR tIP. Male paratype. MORPHOLOGIcALLy cONSIStENt WItH HOLOtyPE, SMALLER, CL/CW RAtIO 0.55. RIGHt cHELIPED WItH 5 ANtERIOR SPINIFORM tEEtH ON MERUS. Female paratypes. FEMALES OF SMALLER SIzE tHAN HOLOtyPE MALE, CL/CW RAtIO 0.58, 0.56, 0.58 FOR FEMALES ORDERED by INcREASING SIzE, RESPEctIVELy. SHAPE IS cONSIStENt WItH tHAt OF MALES, EXcEPt SEcONDARy SEXUAL cHARActERS. PLEON tRIANGULAR WItH ALMOSt StRAIGHt SIDES IN tWO SMALLER FEMALES. PLEON OF LARGESt FEMALE bROADLy tRIANGULAR, LAtERALLy cONVEX, WItH DIStINct tRANSVERSAL RIDGE ON EAcH PLEOMERE 4, 5; PLEOMERE 6 bROADLy ROUNDED, ALMOSt SEMIcIRcULAR; tELSON SMALL, SLIGHtLy LONGER tHAN WIDE, WItH ROUNDED tIP. VULVAE (FIG. 3D) LOcAtED ON StERNAL SUtURES 5/6 ON SIDES OF PLEONAL cAVIty; MEDIAL (INNER) SIDE OF OVAL MARGIN INDIStINct, LAtERAL (OUtER) MARGIN DEFINED by PAIR OF cLOSELy SEt DIStINct ROUNDED tUbERcLES SUbDIVIDED by RESPEctIVE StERNAL SUtURE, tUbERcLES MEDIALLy OVERHANGING LAtERALLy DIREctED GONOPORE ON bOttOM OF VULVA. Colouration. THE GENERAL cOLOUR OF tHE cARAPAcE AND cHELIPEDS IS yELLOWISH bROWN WItH RED AND WHItE PAtcHES OF GRANULES, WHIcH IS ALSO VISIbLE ON FRESHLy PRESERVED SPEcIMENS (FIG. 1). SEGMENtS AND DActyLI OF tHE AMbULAtORy LEGS, INcLUDING cHELIPEDS, ARE PURPLE. THERE IS A RELAtIVELy SMALL bUt WELL-DEFINED ROUNDED DARk PURPLE SPOt WItH A WHItE OUtLINE ON tHE DIStAL END OF tHE DActyLUS OF tHE SWIMMING LEG. OUtER RIDGES OF tHE cHELIPEDS PALM, OUtER cARPAL tOOtH, AND PLEONAL cREStS ARE DIStINctLy IRIDEScENt. Etymology. DUE tO tHE VERy StRIkING IRIDEScENcE OF VARIOUS bODy PARtS IN DAyLIGHt, tHE LAtIN WORD ��� lucidus ��� (SHINy) IS PROPOSED FOR tHE SPEcIES NAME. Remarks. SWIMMING cRAbS OF tHE GENUS Monomia GIStEL, 1848 ARE cHARActERISED by MODERAtELy bROAD ANtEROLAtERAL tEEtH, LARGE ORbItS ON tHE cARAPAcE, tHE bASAL ANtENNAL SEGMENt WItH A bLUNt LObIFORM LAtERAL PROcESS ENtERING tHE ORbIt, A SLIGHtLy PRODUcED EPIStOME, AND tHE DIStINct ANtEROLAtERAL ANGLE OF tHE MERUS OF tHE tHIRD MAXILLIPED (ALcOck 1899). THE GENUS Monomia cURRENtLy cONtAINS 12 SPEcIES (NG et al. 2008; KOcH et al. 2015) DIStRIbUtED IN tHE INDO-WESt PAcIFIc AREA. SEVEN OF tHOSE SPEcIES ARE EASILy DIStINGUISHAbLE FROM M. lucida sp. nov.: M. rubromarginata (LANcHEStER, 1900), M. lecromi (MOOSA, 1996), AND M. calla KOcH, NGUyEN & ĎURI��, 2015, IN HAVING ONLy ONE tOOtH ON tHE POStERIOR bORDER OF tHE cHELIPED MERUS (LANcHEStER 1900; MOOSA 1996; KOcH et al. 2015), versus tWO tEEtH POStERIORLy ON tHE cHELIPED MERUS IN M. lucida sp. nov. Monomia petrea (ALcOck, 1899) POSSESSES A VERy LONG tOOtH ON tHE INNER SURFAcE OF tHE cHELIPED cARPUS, WHILE It IS SHORt IN M. lucida sp. nov. FOR M. euglypha (LAURIE, 1906), tHE SUbHEXAGONAL SHAPE OF ItS cARAPAcE WItH tHE DIStOLAtERAL MARGIN SINUAtE DUE tO A DIStINctLy bROADENED, POStERIORLy EXPANDED bASE OF tHE MOSt POStERIOR LAtERAL tOOtH, AND StRAIGHt, StOUt G1, ARE cHARActERIStIc (versus WItH AN ANtERIORLy SUbcIRcULAR cARAPAcE WItH A DEEPLy INcISED POStEROLAtERAL MARGINS DUE tO tHE cARAPAcE bEING StRONGLy NARROWED POStERIORLy tO tHE LEVEL OF tHE LAtERAL SPINES, AND StRONGLy cURVED AND SLENDER G1, IN M. lucida sp. nov.). Monomia curvipenis (StEPHENSON, 1961), AND M. australiensis (StEPHENSON & COOk, 1973) MAy ALSO bE DIStINGUISHED FROM tHE NEW SPEcIES by tHE SHAPE OF tHE G1; FURtHERMORE, tHE DIStAL PARt OF tHE MALE PLEON WItH tHE tELSON IS SHARPLy tRIANGULAR IN tHE tWO LAttER SPEcIES (versus PLEOMERE 6 WItH LAtERAL MARGINS cONVEX, SUbPARALLEL, WItH bROADLy ROUNDED DIStOLAtERAL ANGLES IN M. lucida sp. nov.). BASED ON PHOtOGRAPHS OF tHE tyPE SPEcIMENS OF Portunus ponticus FAbRIcIUS, 1798 (JENSEN 2006), ItS AFFILIAtION tO tHE GENUS Monomia (E.G. NG et al. 2008) MAy NEED tO bE REVISED. THE REMAINING FOUR SPEcIES, M. argentata, M. gladiator (FAbRIcIUS, 1798), M. pseudoargentata (StEPHENSON, 1961), AND M. samoensis (WARD, 1939), SEEM tO bE cLOSELy RELAtED tO M. lucida sp. nov. THE G1 OF M. pseudoargentata AND M. gladiator ARE ALSO SLENDER bUt LONGER, LESS cURVED, AND tHE cUtIcLE OF tHEIR bODy LAckS tHE IRIDEScENcE tyPIcAL FOR M. lucida sp. nov., AND M. argentata (SEE DAI & YANG 1991). A SUItE OF cHARActERS DIStINGUISHES M. argentata FROM M. lucida sp. nov.: (1) SHARP SPINIFORM ANtEROLAtERAL tEEtH OF tHE cARAPAcE (KOcH et al. 2017: FIG. 7A), versus bEING StOUt AND FORWARD DIREctED IN tHE NEW SPEcIES (FIGS 1, 2A); (2) tHE MALE PLEON WItH LAtERAL MARGINS OF tHE SIXtH PLEOMERE cONVEX, ANtERIORLy cONVERGENt (KOcH et al. 2017: FIG. 7B), versus SUbPARALLEL MARGINS WItH ROUNDED DIStAL SHOULDERS MEEtING tHE MUcH NARROWER tELSON (FIG. 2B); (3) FEMALE PLEON WItH A SHORt, GLAbROUS tRANSVERSE RIDGE ON PLEOMERE 4 ONLy (KOcH et al. 2017: FIG. 8E), versus A LONG tRANSVERSE RIDGE ON bOtH PLEOMERES 4 AND 5 (FIG. 3C); (4) RELAtIVELy NARROW cHELA, A LONG DIStODORSAL SPINE ON tHE cARPUS (KOcH et al. 2017: FIG. 7D), versus RELAtIVELy StOUt cHELA AND A REDUcED SPINE (FIG. 2D); (5) StOUt G1 WItH A bLUNt APEX (KOcH et al. 2017: FIG. 4), versus LONG, SLENDER, REctANGULAR cURVED G1 WItH A NON-EXPANDED APEX (FIG. 3A); (6) A DARk SPOt WItH DIFFUSED MARGIN ON tHE SWIMMING DActyLUS (KOcH et al. 2017: FIG. 5), versus A WELL- DEFINED, ROUNDED, WHItE OUtLINED DARk SPOt IN tHE NEW SPEcIES (FIG. 1). THE ActUAL RANGE OF M. lucida sp. nov. IS UNcLEAR, AS PREVIOUS REPORtS OF M. argentata MIGHt ALSO cOVER tHE PRESENt NEW SPEcIES. ONLy SOME OF tHE PREVIOUS DEScRIPtIONS PROVIDE DEtAILS ON tHE SHAPE OF tHE MALE PLEON AND GONOPODS (BARNARD 1950; EDMONDSON 1954; CROSNIER 1962; StEPHENSON & REES 1967A, b), OR tHE cOLOUR PAttERN (CHERtOPRUD et al. 2012), ALLOWING tHEM tO bE cOMPARED WItH tHE PRESENt NEW SPEcIES. StEPHENSON & REES (1967b: FIG 2A, E) ILLUStRAtED tHE G1 OF ��� M. argentata ��� FROM WEStERN INDIA, AND CHERtOPRUD et al. (2012) REPORtED ON LARGER bODIED SPEcIMENS OF ��� M. argentata ��� FROM VIEtNAM (UP tO CW 46 MM), AND PROVIDED A cOLOUR PHOtOGRAPH (CHERtOPRUD et al. 2012: PL. 51F), WHIcH ALL cLEARLy IDENtIFy At LEASt SOME tHEIR SPEcIMENS AS bELONGING tO tHE PRESENt NEW SPEcIES. THUS, FOR NOW tHE kNOWN RANGE OF M. lucida sp. nov. IS LIMItED tO VIEtNAM (SOUtH CHINA SEA) AND NORtH-WEStERN INDIA (ARAbIAN SEA). THE SyStEMAtIc StAtUS OF ANOtHER SPEcIES, M. samoensis (WARD, 1939), IS UNcLEAR AS It WAS DEScRIbED FROM A SINGLE SMALL jUVENILE MALE (FIG. 5) FROM SAMOA. OUR RE-EXAMINAtION OF tHE HOLOtyPE (AMNH 7482; 8.5 X 15 MM OF tHE cARAPAcE SIzE) HAS REVEALED tHAt tHE PLEON OF M. samoensis IS SUbtRIANGULAR, tAPERING DIStALLy. THE SPEcIMEN HAS UNDEVELOPED GONOPODS, bUt tHE FUSED PLEOMERES 3���5 cONFIRM It IS A MALE. THE DIStRIbUtION OF PAtcHES OF GRANULES DORSALLy ON tHE cARAPAcE DIFFERS FROM tHAt DEScRIbED HERE FOR M. lucida sp. nov., AND tHE ANtEROLAtERAL MARGIN IS PROPORtIONALLy DIStINctLy LONGER. THE DARk SPOt ON tHE LASt SEGMENt OF tHE SWIMMING LEG IS LARGE AND NOt cIRcULAR, AS IS ALSO EVIDENt FROM tHE ORIGINAL PHOtOGRAPHS OF M. samoensis PROVIDED by WARD (1939: FIGS. 5, 6). THE EXtERNAL MORPHOLOGy OF tHE PRESERVED HOLOtyPE ARE SHOWN AGAIN HERE (FIG. 7A, B). ItS SPEcIFIc StAtUS MIGHt bE REVISED IN tHE FUtURE bASED ON FRESHLy cOLLEctED tOPOtyPIc SPEcIMENS. ALcOck (1899) MENtIONED A VARIEty ��� Neptunus argentatus VAR. glareosus ��� FROM tHE ANDAMAN ISLANDS tHAt MIGHt ALSO bELONG tO tHE M. argentata SPEcIES cOMPLEX. AccORDING tO tHE DEScRIPtION by ALcOck (1899), SPEcIMENS OF tHIS tAXON ARE cOMPLEtELy WItHOUt tOMENtUM ON tHEIR cARAPAcE, WHILE tHE cARAPAcE DORSUM AND PLEON OF M. argentata, s. str., AND M. lucida sp. nov., ARE DENSELy cOVERED by FINE PILA. THE FORMER SPEcIMENS ALSO POSSESS A HIGH tHIN cRESt ON PLEONAL SEGMENt 3, REPORtED AS bEING ���tWIcE AS PROMINENt AS IS IN tHE tyPIcAL FORM��� (ALcOck, Published as part of Koch, Milan & ��uri��, Zden��k, 2018, Monomia lucida sp. nov., a new swimming crab (Crustacea: Decapoda: Portunidae) from the South China Sea, pp. 567-579 in Zootaxa 4387 (3) on pages 569-576, DOI: 10.11646/zootaxa.4387.3.9, http://zenodo.org/record/1187765, {"references":["GiSTel, H. (1848) Naturgeschichte des Thierreichs fur hohere Schulen bearbeites. ScHeiTliN & KrAiS, STuTTgArT, xvi + 220 PP. HTTPS: // dOi. Org / 10.5962 / bHl. TiTle. 97235"]}

Koch, Milan, Nguyen, Thanh Son, Ďuriš, Zdeněk (2015): Monomia calla, a new species of swimming crab (Decapoda, Portunidae) from Madagascar and the Philippines. Zootaxa 3981 (3): 405-412, DOI: http://dx.doi.org/10.11646/zootaxa.3981.3.6

Monomia calla sp. nov. (Figs 1–4) Material. 1 male, holotype, CW 33.5 mm, MNHN-IU- 2014-10105; South off Sainte Marie Cape, 26 °08' S – 46 °04' E, south of Madagascar; Atimo Vatae Expedition, 14 May, 2010, fishery vessel Nosy Be 11, stn CP 3611, 106 – 111 m. Additional material. 1 male, CW 38.4 mm, ZRC 2001.0633; Philippines: Balicasag Island, Bohol, 28 Nov. 2001, coll. by local fishermen, tangle nets, 50– 500 m. Description of male holotype. Carapace (Figs 1 A, 2 A) subcircular, CL/CW ratio 0.66. Front width 0.18 of CW, frontal region including inner orbital tooth 0.27 of CW, fronto-orbital width (between tips of outer orbital teeth) 0.55 of CW. Front subdivided into 4 distinct subequal triangular teeth, median pair distinctly narrower than lateral, with median notch slightly shorter than more lateral ones. Inner orbital angle reaching half of lateral frontal teeth, obtusely angulate, with lateral part of dorsal surface finely granular, median part smooth. Supraorbital margin granular, with 2 well-developed notches medially, on base of first anterolateral tooth. Infraorbital margin strongly granular, with narrow, very deep lateral notch, with tooth-like elevation on ventral side of first anterolateral tooth. Anterolateral margin convex, with 9 forward projecting teeth with granular margins; first tooth larger, with sinuous outer margin, rounded tip; second to eighth teeth subequal in size, sharp; ninth tooth about double size of preceding ones. Posterolateral margin slightly granular, concave, slightly shorter than anterolateral margin; posterolateral angle rounded; posterior margin finely granular, slightly convex. Dorsal surface of carapace densely covered by short tomentum. Regions well defined, elevated, bounded by patches of distinct knob-like granules; anterior median elevation forming cross-like structure with mesogastric granular patches, connected by smooth area with granular metagastric regions; latter regions with transverse line of granules anteriorly; mesobranchial regions subdivided into 4 patches of granules; anterolateral regions fringed by groups of granules; cardiac, lateral postcardiac, median postcardiac regions each with simple granular patch. Epistome well defined, median tooth projecting beyond posterior angle of median frontal incision. Surface of male thoracic sternites (Fig. 1 B) finely tomentose, sternites 2–5 roughly granular; sternite 6 granular along anterior, lateral margins; sternites 7, 8 smooth; sternites 3, 4 fused, without distinct sulcus; sternite 4 with deep median groove; sternites 5–8 well defined. Abdomen (Figs 1 B, 2 B) T-shaped, outer surface densely tomentose; posterior abdominal margin forming pair of subparallel tranverse laminar crests on each of somites 2, 3 slightly sinuous, with median concavity on somite 3, median convexity on somite 2; lateral margins of somite 3 almost straight, oblique, with subrectangular angles; somites 3–5 fused, sulcus between somites 4, 5 inconspicuous, sulcus between somites 3, 4 reduced to short central groove; elevated submarginal ridge posteriorly present on somite 4; somite 6 robust, subrectangular, 2 times longer than telson, 1.1 times longer than wide distally, lateral margins subparallel, slightly diverging distally, with rounded anterolateral angles distinctly elevated laterally, with pair of low but distinct distolateral swellings covering tips of male first gonopods, somewhat less elevated regions covering bases of male first gonopods on proximolaterally part of somite 4; telson narrowly triangular, 1.3 times longer than basal width, with rounded tip, posterior margin broadly rounded. Third maxillipeds (Fig. 2 C) distinctly granular on ischium, merus, exopodal peduncle, with densely setose margins; palp (dactylus, propodus, carpus) tapering distally, with segments subcylindrical; merus subquadrate, with lateral, mesial glabrous fields, anterolateral angle forming widely subtriangular projection; ischium about 2.0 times merus length, 1.7 times as long as wide, with longitudinal glabrous sulcus. Exopod relatively stout, about half of ischium width, with subdistal triangular projection on inner medial border; flagellum longer than merus width. Chelipeds (Figs 1 A, 2 D) symmetrical, relatively robust, with chela length subequal to CW. Merus with 4 spines on anterior, one glabrous, depressed, spine on posterior border. Carpus with 1 sharp, long, inner spine, one flattened outer spine; 3 distinct carinae on dorsal surface, with 2 of latters terminating as spines (see above). Upper surface of palm with 2 granular crests, inner one ending by spine distally, outer surface with distinct spiniform proximal tooth over articulation with carpus, with 2 granular crests ending on level of finger joint; inner surface of palm with obtuse longitudinal keel dividing ventromesial, ventrolateral surfaces of squamiform transverse ridges; fingers straight, tapering, 0.7 of maximum palm length, distinctly carinate. Movable finger of right chela with distinct slightly elongated molariform tooth proximally on cutting edge, left chela with bilobed conical teeth on such position. Fingers otherwise with bi-, trilobed serial conical teeth separated by small single lobes. Fifth ambulatory leg with merus finely serrate on both antero-, posterodistal angles. Dactylus oval, 2.4 times longer than maximum width, broadly rounded distally, with longitudinal median sulcus; upper surface finely pilose, with 4 longitudinal glabrous patches submedially, marginally. Male first gonopod (Fig. 1 C–E) with proximal part swollen but tapering distally, situated obliquely to median body plane, distal half slender, parallel to body plane, flattened in oblique plane facing ventrolaterally, apex bended laterally, subterminally widened to oblique funnel with ventrally opened longitudinal groove, dorsal margin membranous, tip recurved medially. Variation in Philippine specimen (Figs. 3, 4). The Philippine specimen is very similar to the holotype and consistent in the majority of the characters. Most significantly, the male first gonopods of both the specimens are almost identical. The carapace of the Philippine specimen, however, is relatively broader, with the CW/CL ratio 1.7 (1.55 in the holotype); the frontal and anterolateral teeth are more slender, sharper, with the last (lateral) tooth a bit longer; the angle of the posterolateral margin posterior to the lateral tooth is more subquadrate (broadly rounded in the holotype); the chelipeds have the carpal and palmar teeth relatively more robust, with the merus shorter and stouter, and with 3 spines on the anterior border of the merus (4 spines in the holotype); the sixth pleomere of abdomen with more sinuous lateral margins (vs. more straight and angular); and the telson lightly shorter (Fig 3 B). Measurements [in mm]. Holotype: CW 33.5, CL 22.4, fronto-orbital length 18.1, frontal length 8.9, right/left chela length 27.6 / 27.9, right/left finger length 13.4 / 13.7. Coloration. The holotype specimen was preserved for some time in ethanol but residual red spots are visible (Fig. 1 A) on the tips of the anterolateral teeth of the carapace, on the front, on the anterior border of the manus and carpus of the chela, and on both the inner surface of the palm and the movable finger. Etymology. This species is named after the flower of the calla lily, a plant of the genus Zantedeschia, family Aracea, to which the shape of the male first gonopod of the new species resembles. The name is used as a noun in apposition. Remarks. The subgeneric name Monomia was established by Gistel (1848) as a substitution for De Haan’s (1833) name Amphitrite, which was established for a group of Portunus species (type species P. gladiator Fabricius, 1798). Amphitrite Mueller, 1771, the senior homonym, is a genus of polychaete worms (Ng et al. 2008). Its subgeneric status has been accepted by most authors in recent years, except Barnard (1950), who used it as the generic name for two South African species, M. argentata (A. Milne-Edwards 1861), and M. gladiator (Fabricius, 1798). Ng et al. (2008) recognised 11 species in the genus (as a subgenus). Chertoprud et al. (2012: 312) more recently used the name at generic level for M. pseudoargentata (Stephenson, 1961), in addition to the two species by Barnard (1950), citing other studies that suggested the various subgenera of Portunus are all valid genera. We agree at least in as far as Monomia Gistel, 1848, is concerned its member species can all be characterised by the following characters: moderately broad and dorsally slightly convex carapace with large orbits and large anterolateral teeth, and with rounded posterolateral angles; basal antennal segment forming a blunt lobiform process; epistome slightly produced into a median tooth; and merus of the third maxilliped with a produced anterolateral angle (cf. Alcock 1899; Barnard 1950). Monomia calla sp. nov. can be distinguished from all other congeners by the unique shape of the male first gonopod, terminating into a widened, funnel-like tip. Compared to most congeners, the new species also differs by the presence of a single posterior meral tooth on the chelipeds, and by the front of the carapace subdivided into four subtriangular teeth of almost the same size. In contrast, the majority of congeners, i.e., M. argentata, M. australiensis (Stephenson & Cook, 1973), M. curvipenis (Stephenson, 1961), M. euglypha (Laurie, 1906), M. gladiator, M. petrea (Alcock, 1899), M. pseudoargentata, and M. samoensis Ward, 1939, possess two spines on the posterior margin of the merus of the cheliped, and have low submedian frontal teeth (cf. A. Milne-Edwards 1861: 332; Alcock 1899: 35-38; Ward 1939: Figs. 5, 6; Stephenson 1961: Pl. 2, Figs. 3, 4; Stephenson & Cook 1973: Figs. 6-10). Ng et al. (2008: 152) resurrected Portunus ponticus Fabricius, 1798, as a distinct species, briefly commenting that it was close to M. gladiator. We examined photographs of the types of Monomia pontica in the Zoology Museum of the University of Copenhagen (Jensen 2006) and it clearly differs from the new species by the presence of transverse crests (instead of patches of granules) on the dorsum of the carapace, the submedian frontal teeth produced beyond lateral teeth (subequal in the new species), distinctly elongate chelipeds with palms much more slender than the merus (with stout palm in the new species), and the presence of two sharp teeth dorsally on the distal part of the palm (one tooth in the new species). Monomia rubromarginata (Lanchester, 1900) and M. lecromi (Moosa, 1996) are morphologically closest to M. calla sp. nov. due to the presence of one tooth on the posterior margin of the cheliped merus, with sharp and distinct frontal teeth, and with a similar shape of the merus of the third maxilliped. There are nevertheless some significant differences between these two species and the new species: males have the abdomen with a trapezoid penultimate segment (relatively quadrangular in the new species), with its lateral outline clearly continuing to the lateral borders of the telson, and an almost straight, distally simple, male first gonopod (twisted gonopod with a funnel-shaped tip in the new species) (cf. Lanchester 1900; Stephenson & Campbell 1959; Moosa 1996). The closest congeners of M. calla sp. nov. are from the Western Pacific: M. lecromi was reported only from the Chesterfield Islands, Coral Sea (Moosa 1996), whereas M. rubromarginata has been recorded from Singapore (Lanchester 1900), the South China Sea and the Malay Archipelago (Shen 1937), as well as the northern half of Australia (Stephenson & Campbell 1959). The wide geographical distance between the localities of the new species, Madagascar and Philippines, together with some morphological distinctions reported above, is intriguing. While the observed morphological differences are not very major, the fact remains that only two specimens are known, and their male first gonopod structures are very similar. More specimens will need to be obtained to ascertain the degree the variation, perhaps also with additional genetic studies conducted. The species name “ Portunus (Monomia) calla ” was first used by Nguyen (2013) in his thesis, but as the work is not published, the name is not available. With the description of Monomia calla sp. nov., 12 species are now known in the genus. Distribution. Known from the type locality, south off Madagascar, the western Indian Ocean and Bohol Island, Philippines, the Sulu Sea.

Monomia calla sp. nov. (Figs 1���4) Material. 1 male, holotype, CW 33.5 mm, MNHN-IU- 2014-10105; South off Sainte Marie Cape, 26 ��08' S ��� 46 ��04' E, south of Madagascar; Atimo Vatae Expedition, 14 May, 2010, fishery vessel Nosy Be 11, stn CP 3611, 106 ��� 111 m. Additional material. 1 male, CW 38.4 mm, ZRC 2001.0633; Philippines: Balicasag Island, Bohol, 28 Nov. 2001, coll. by local fishermen, tangle nets, 50��� 500 m. Description of male holotype. Carapace (Figs 1 A, 2 A) subcircular, CL/CW ratio 0.66. Front width 0.18 of CW, frontal region including inner orbital tooth 0.27 of CW, fronto-orbital width (between tips of outer orbital teeth) 0.55 of CW. Front subdivided into 4 distinct subequal triangular teeth, median pair distinctly narrower than lateral, with median notch slightly shorter than more lateral ones. Inner orbital angle reaching half of lateral frontal teeth, obtusely angulate, with lateral part of dorsal surface finely granular, median part smooth. Supraorbital margin granular, with 2 well-developed notches medially, on base of first anterolateral tooth. Infraorbital margin strongly granular, with narrow, very deep lateral notch, with tooth-like elevation on ventral side of first anterolateral tooth. Anterolateral margin convex, with 9 forward projecting teeth with granular margins; first tooth larger, with sinuous outer margin, rounded tip; second to eighth teeth subequal in size, sharp; ninth tooth about double size of preceding ones. Posterolateral margin slightly granular, concave, slightly shorter than anterolateral margin; posterolateral angle rounded; posterior margin finely granular, slightly convex. Dorsal surface of carapace densely covered by short tomentum. Regions well defined, elevated, bounded by patches of distinct knob-like granules; anterior median elevation forming cross-like structure with mesogastric granular patches, connected by smooth area with granular metagastric regions; latter regions with transverse line of granules anteriorly; mesobranchial regions subdivided into 4 patches of granules; anterolateral regions fringed by groups of granules; cardiac, lateral postcardiac, median postcardiac regions each with simple granular patch. Epistome well defined, median tooth projecting beyond posterior angle of median frontal incision. Surface of male thoracic sternites (Fig. 1 B) finely tomentose, sternites 2���5 roughly granular; sternite 6 granular along anterior, lateral margins; sternites 7, 8 smooth; sternites 3, 4 fused, without distinct sulcus; sternite 4 with deep median groove; sternites 5���8 well defined. Abdomen (Figs 1 B, 2 B) T-shaped, outer surface densely tomentose; posterior abdominal margin forming pair of subparallel tranverse laminar crests on each of somites 2, 3 slightly sinuous, with median concavity on somite 3, median convexity on somite 2; lateral margins of somite 3 almost straight, oblique, with subrectangular angles; somites 3���5 fused, sulcus between somites 4, 5 inconspicuous, sulcus between somites 3, 4 reduced to short central groove; elevated submarginal ridge posteriorly present on somite 4; somite 6 robust, subrectangular, 2 times longer than telson, 1.1 times longer than wide distally, lateral margins subparallel, slightly diverging distally, with rounded anterolateral angles distinctly elevated laterally, with pair of low but distinct distolateral swellings covering tips of male first gonopods, somewhat less elevated regions covering bases of male first gonopods on proximolaterally part of somite 4; telson narrowly triangular, 1.3 times longer than basal width, with rounded tip, posterior margin broadly rounded. Third maxillipeds (Fig. 2 C) distinctly granular on ischium, merus, exopodal peduncle, with densely setose margins; palp (dactylus, propodus, carpus) tapering distally, with segments subcylindrical; merus subquadrate, with lateral, mesial glabrous fields, anterolateral angle forming widely subtriangular projection; ischium about 2.0 times merus length, 1.7 times as long as wide, with longitudinal glabrous sulcus. Exopod relatively stout, about half of ischium width, with subdistal triangular projection on inner medial border; flagellum longer than merus width. Chelipeds (Figs 1 A, 2 D) symmetrical, relatively robust, with chela length subequal to CW. Merus with 4 spines on anterior, one glabrous, depressed, spine on posterior border. Carpus with 1 sharp, long, inner spine, one flattened outer spine; 3 distinct carinae on dorsal surface, with 2 of latters terminating as spines (see above). Upper surface of palm with 2 granular crests, inner one ending by spine distally, outer surface with distinct spiniform proximal tooth over articulation with carpus, with 2 granular crests ending on level of finger joint; inner surface of palm with obtuse longitudinal keel dividing ventromesial, ventrolateral surfaces of squamiform transverse ridges; fingers straight, tapering, 0.7 of maximum palm length, distinctly carinate. Movable finger of right chela with distinct slightly elongated molariform tooth proximally on cutting edge, left chela with bilobed conical teeth on such position. Fingers otherwise with bi-, trilobed serial conical teeth separated by small single lobes. Fifth ambulatory leg with merus finely serrate on both antero-, posterodistal angles. Dactylus oval, 2.4 times longer than maximum width, broadly rounded distally, with longitudinal median sulcus; upper surface finely pilose, with 4 longitudinal glabrous patches submedially, marginally. Male first gonopod (Fig. 1 C���E) with proximal part swollen but tapering distally, situated obliquely to median body plane, distal half slender, parallel to body plane, flattened in oblique plane facing ventrolaterally, apex bended laterally, subterminally widened to oblique funnel with ventrally opened longitudinal groove, dorsal margin membranous, tip recurved medially. Variation in Philippine specimen (Figs. 3, 4). The Philippine specimen is very similar to the holotype and consistent in the majority of the characters. Most significantly, the male first gonopods of both the specimens are almost identical. The carapace of the Philippine specimen, however, is relatively broader, with the CW/CL ratio 1.7 (1.55 in the holotype); the frontal and anterolateral teeth are more slender, sharper, with the last (lateral) tooth a bit longer; the angle of the posterolateral margin posterior to the lateral tooth is more subquadrate (broadly rounded in the holotype); the chelipeds have the carpal and palmar teeth relatively more robust, with the merus shorter and stouter, and with 3 spines on the anterior border of the merus (4 spines in the holotype); the sixth pleomere of abdomen with more sinuous lateral margins (vs. more straight and angular); and the telson lightly shorter (Fig 3 B). Measurements [in mm]. Holotype: CW 33.5, CL 22.4, fronto-orbital length 18.1, frontal length 8.9, right/left chela length 27.6 / 27.9, right/left finger length 13.4 / 13.7. Coloration. The holotype specimen was preserved for some time in ethanol but residual red spots are visible (Fig. 1 A) on the tips of the anterolateral teeth of the carapace, on the front, on the anterior border of the manus and carpus of the chela, and on both the inner surface of the palm and the movable finger. Etymology. This species is named after the flower of the calla lily, a plant of the genus Zantedeschia, family Aracea, to which the shape of the male first gonopod of the new species resembles. The name is used as a noun in apposition. Remarks. The subgeneric name Monomia was established by Gistel (1848) as a substitution for De Haan���s (1833) name Amphitrite, which was established for a group of Portunus species (type species P. gladiator Fabricius, 1798). Amphitrite Mueller, 1771, the senior homonym, is a genus of polychaete worms (Ng et al. 2008). Its subgeneric status has been accepted by most authors in recent years, except Barnard (1950), who used it as the generic name for two South African species, M. argentata (A. Milne-Edwards 1861), and M. gladiator (Fabricius, 1798). Ng et al. (2008) recognised 11 species in the genus (as a subgenus). Chertoprud et al. (2012: 312) more recently used the name at generic level for M. pseudoargentata (Stephenson, 1961), in addition to the two species by Barnard (1950), citing other studies that suggested the various subgenera of Portunus are all valid genera. We agree at least in as far as Monomia Gistel, 1848, is concerned its member species can all be characterised by the following characters: moderately broad and dorsally slightly convex carapace with large orbits and large anterolateral teeth, and with rounded posterolateral angles; basal antennal segment forming a blunt lobiform process; epistome slightly produced into a median tooth; and merus of the third maxilliped with a produced anterolateral angle (cf. Alcock 1899; Barnard 1950). Monomia calla sp. nov. can be distinguished from all other congeners by the unique shape of the male first gonopod, terminating into a widened, funnel-like tip. Compared to most congeners, the new species also differs by the presence of a single posterior meral tooth on the chelipeds, and by the front of the carapace subdivided into four subtriangular teeth of almost the same size. In contrast, the majority of congeners, i.e., M. argentata, M. australiensis (Stephenson & Cook, 1973), M. curvipenis (Stephenson, 1961), M. euglypha (Laurie, 1906), M. gladiator, M. petrea (Alcock, 1899), M. pseudoargentata, and M. samoensis Ward, 1939, possess two spines on the posterior margin of the merus of the cheliped, and have low submedian frontal teeth (cf. A. Milne-Edwards 1861: 332; Alcock 1899: 35-38; Ward 1939: Figs. 5, 6; Stephenson 1961: Pl. 2, Figs. 3, 4; Stephenson & Cook 1973: Figs. 6-10). Ng et al. (2008: 152) resurrected Portunus ponticus Fabricius, 1798, as a distinct species, briefly commenting that it was close to M. gladiator. We examined photographs of the types of Monomia pontica in the Zoology Museum of the University of Copenhagen (Jensen 2006) and it clearly differs from the new species by the presence of transverse crests (instead of patches of granules) on the dorsum of the carapace, the submedian frontal teeth produced beyond lateral teeth (subequal in the new species), distinctly elongate chelipeds with palms much more slender than the merus (with stout palm in the new species), and the presence of two sharp teeth dorsally on the distal part of the palm (one tooth in the new species). Monomia rubromarginata (Lanchester, 1900) and M. lecromi (Moosa, 1996) are morphologically closest to M. calla sp. nov. due to the presence of one tooth on the posterior margin of the cheliped merus, with sharp and distinct frontal teeth, and with a similar shape of the merus of the third maxilliped. There are nevertheless some significant differences between these two species and the new species: males have the abdomen with a trapezoid penultimate segment (relatively quadrangular in the new species), with its lateral outline clearly continuing to the lateral borders of the telson, and an almost straight, distally simple, male first gonopod (twisted gonopod with a funnel-shaped tip in the new species) (cf. Lanchester 1900; Stephenson & Campbell 1959; Moosa 1996). The closest congeners of M. calla sp. nov. are from the Western Pacific: M. lecromi was reported only from the Chesterfield Islands, Coral Sea (Moosa 1996), whereas M. rubromarginata has been recorded from Singapore (Lanchester 1900), the South China Sea and the Malay Archipelago (Shen 1937), as well as the northern half of Australia (Stephenson & Campbell 1959). The wide geographical distance between the localities of the new species, Madagascar and Philippines, together with some morphological distinctions reported above, is intriguing. While the observed morphological differences are not very major, the fact remains that only two specimens are known, and their male first gonopod structures are very similar. More specimens will need to be obtained to ascertain the degree the variation, perhaps also with additional genetic studies conducted. The species name ��� Portunus (Monomia) calla ��� was first used by Nguyen (2013) in his thesis, but as the work is not published, the name is not available. With the description of Monomia calla sp. nov., 12 species are now known in the genus. Distribution. Known from the type locality, south off Madagascar, the western Indian Ocean and Bohol Island, Philippines, the Sulu Sea., Published as part of Koch, Milan, Nguyen, Thanh Son & ��uri��, Zden��k, 2015, Monomia calla, a new species of swimming crab (Decapoda, Portunidae) from Madagascar and the Philippines, pp. 405-412 in Zootaxa 3981 (3) on pages 406-411, DOI: 10.11646/zootaxa.3981.3.6, http://zenodo.org/record/234737, {"references":["Gistel, J. (1848) Naturgeschichte des Thierreiches fur hohere Schulen bearbeitet. Hoffmann'she Verlags Buchhandlung, Stuttgart, xvi, 216 pp., pls. 1 - 32.","Barnard, K. H. (1950) Descriptive catalogue of South African decapod Crustacea (crabs and shrimps). Annals of the South African Museum, 38, 1 - 837.","Chertoprud, E. S., Spiridonov, V. A., Ponomarev, S. A., Mokievsky, V. O. (2012) Commercial crabs (Crustacea Decapoda Brachyura) from Nhatrang Bay (Vietnam). In: Britaev, T. A. (Ed.), Benthic fauna of the Nhatrang Bay. Vol. 2. KMK Scientific Press, Moscow, pp. 301 - 349.","Stephenson, W. (1961) The Australian portunids (Crustacea: Portunidae). V Recent collections. Australian Journal of Marine and Freshwater Research, 12, 92 - 128. http: // dx. doi. org / 10.1071 / MF 9610092","Alcock, A. (1899) Materials for a carcinological fauna of India. No. 4. The Brachyura Cyclometopa. Part II. A revision of the Cyclometopa with an account of the families Portunidae, Cancridae and Corystidae. Journal of the Asiatic Society of Bengal, 68, 1 - 104.","Stephenson, W. & Cook, S. (1973) Studies of Portunus gladiator complex and related species of Portunus (Crustacea: Decapoda). Memoirs of the Queensland Museum, 16 (3), 415 - 434.","Laurie, R. D. (1906) Report on the Brachyura collected by Professor Herdman, at Ceylon, in 1902. In: Herdman, W. A. (Ed.), Report to the Government of Ceylon on the Pearl Oyster Fisheries of the Gulf of Manaar with Supplementary Reports Upon the Marine Biology of Ceylon by Other Naturalists, Part 5, 40 (Supplement), 349 - 432, pls. 1 - 2.","Ward, M. (1939) The Brachyura of the second Templeton Crocker-American Museum Expedition to the Pacific Ocean. American Museum Novitates, 1049, 1 - 13.","Jensen, M. T. (Ed.) (2006) Crustacea types by J. C. Fabricius at the Zoological Museum, University of Copenhagen. ZMUC, Invertebrate Department. Available from: http: // www. zmuc. dk / inverweb / invertebrater / Crustacea % 20 databases / Fabricius % 20 collection. htm (accessed 10 January 2015)","Lanchester, W. F. (1900) On a collection of crustaceans made at Singapore and Malacca. Part I. Crustacea Brachyura. Proceedings of the General Meetings for Scientific Business of the Zoological Society of London, 1900 (3), 719 - 770, pls. 44 - 47.","Moosa, M. K. (1996) Crustacea Decapoda: deep-water swimming crabs from the south-west Pacific, particularly New Caledonia (Brachyura, Portunidae). In: Crosnier, A. (Ed.), Resultats des Campagnes MUSORSTOM. Vol. 15. Memoires du Museum national d'Histoire naturelle, Paris, 168, pp. 503 - 530.","Stephenson, W. & Campbell, B. M. (1959) The Australian portunids (Crustacea: Portunidae). III The genus Portunus. Australian Journal of Marine and Freshwater Research, 10, 84 - 124. http: // dx. doi. org / 10.1071 / MF 9590084","Shen, C. J. (1937) Notes on a collection of swimming crabs (Portunidae) from Singapore. Bulletin of the Raffles Museum, 13, 96 - 139.","Nguyen, T. S. (2013). An annotated checklist of the crabs of the superfamily Portunoidea Rafinesque, 1815, from The Philippines (Crustacea: Decapoda: Brachyura). Unpublished M. Sc. Thesis, National University of Singapore. [unknown pagination]"]}