On a Collection of Rocky Intertidal Xanthid Crabs (Crustacea, Decapoda, Xanthidae) from Taiwan, with Description of a New Species of Cyclodius Dana 1851

© 2024 Academia Sinica, Taiwan Open Access On a Collection of Rocky Intertidal Xanthid Crabs (Crustacea, Decapoda, Xanthidae) from Taiwan, with Description of a New Species of Cyclodius Dana 1851 Pan-Wen Hsueh1,* and You-Wei Tzeng2 1Department of Life Sciences, National Chung Hsing University, Taichung 402, Taiwan. *Correspondence: E-mail: [email protected] (Hsueh) 2Institute of Oceanography, National Taiwan University, Taipei 106, Taiwan. E-mail: [email protected] (Tzeng) urn:lsid:zoobank.org:pub:7A39825B-16DF-4AEC-A3A0-C4587AA59946 Received15 September 2023 / Accepted 9 September 2024 / Published 31 December 2024 Communicated by Benny K.K. Chan Over 110 specimens of xanthid crabs collected from rocky intertidal habitats in Taiwan and its offshore islands over the past 25+ years were examined in the present study. As a result, 24 species were recognized, distributed across seven subfamilies and 16 genera including one new genus record (i.e., Lioxanthodes Calman, 1909) for Taiwan. Of these recognized species, 14 have been previously reported from Taiwan, whereas five are new records for Taiwan, one new to science, and four unnamed species. The five newly recorded species are Chlorodiella barbata (Borradaile, 1900), Etisus frontalis (Dana, 1852), Lioxanthodes alcocki Calman, 1909, and Macromedaeus quinquedentatus (Krauss, 1843), and Pilodius nigrocrinitus Stimpson, 1859. The new species, Cyclodius taiwanensis sp. nov., is herein described. Key words: Brachyuran crabs, Actaeinae, Chlorodiellinae, Etisinae, Euxanthinae, Liomerinae, Xanthinae, Zosiminae, Taxonomy Citation: Hsueh P-W, Tzeng Y-W. 2024. On a collection of rocky intertidal xanthid crabs (Crustacea, Decapoda, Xanthidae) from Taiwan, with description of a new species of Cyclodius Dana 1851. Zool Stud 63:47. doi:10.6620/ZS.2024.63-47. BACKGROUND Xanthid crabs are among the most diverse taxon groups within the brachyurans (Ng et al. 2008; Lai et al. 2011; Mendoza 2021). Surveys on brachyuran diversity in Taiwanese waters have been conducted over 70 years, resulting in annotated checklists documenting the region’s brachyuran crabs. Ng et al. (2001) reported a total of 548 species from Taiwan, representing 36 families, of which 107 species belong to the Xanthidae MacLeay, 1838, distributed across 11 subfamilies and 42 genera. An updated annotated checklist by Ng et al. (2017) increased the number of reported species in Taiwanese waters to 803, spanning 74 families. Of these 803 species, 130 belong to the Xanthidae, distributed across 12 subfamilies and 53 genera. Ng et al. (2017) concluded that more brachyuran species were likely to be discovered in Taiwan’s complex reef habitats. This expectation was supported by a recent report by the author, documenting one new record genus and new species, Garthasia ludaoensis Hsueh, 2020 (family Xanthidae MacLeay, 1838, subfamily Kraussiinae Ng, 1993), and one newly recorded species, Zosimus maculatus (de Man, 1887) (family Xanthidae MacLeay, 1838, subfamily Zosiminae Alcock, 1898), from coral reef habitats in Taiwan (Hsueh 2020). In this study, the authors examined over 110 specimens of xanthid crabs collected during ecological surveys of rocky intertidal habitats in Taiwan over the past 25+ years. A total of 24 species were identified, 14 of which had been previously reported from Taiwan (Table 1). The remaining 10 species included five newly Zoological Studies 63:47 (2024) doi:10.6620/ZS.2024.63-47 1 © 2024 Academia Sinica, Taiwan recorded species, one species new to science, and four unnamed species (Table 1). The unnamed species were primarily female juveniles, with one juvenile male Etisus. Due to the lack of adult features and unknown degrees of variation and ontogenetic changes, these juveniles could not be identified to the species level. The new species, Cyclodius taiwanensis sp. nov., is described herein. MATERIALS AND METHODS Specimens of xanthid crabs were collected from rocky intertidal habitats of Taiwan and nearby offshore islands during ecological surveys conducted over the past 25+ years. Sampling was performed using hammers and chisels at the intertidal collection sites (Fig. 1; see Table 2 for coordinates of the collection sites). The collected specimens were stored in 70% ethanol. The specimens were examined under a stereo microscope (Leica MZ12.5) and a compound microscope (Leica DM2500). Photographic images of the specimens and their body parts were captured using digital cameras (Sony α 200, 10.2 megapixels; Canon EOS 6D Mark II, 26.2 megapixels; and Canon EOS 7D Mark II, 20 megapixels) and enhanced using computer software (Helicon Focus 7.0.2 and PhotoImpact 8). Drawings were created by tracing the outlines of examined body parts and appendages from digitized images using CorelDRAW 2020. The terminology for carapace regions followed Dana (1852b), while the terminology for brachyuran body parts adhered to Davie et al. (2015). Measurements were taken for carapace width and carapace length in millimeter. The abbreviations used include: CW for carapace width; G1 and G2 for the first and second gonopods of males; and P1–P5 for the first to fifth pereiopods (with P1 also referred to as chelipeds and Table 1. Xanthidae taxa identified in the present study. Information on the first record of a given species from Taiwan is based on Ng et al. (2017) Taxon First Record Actaeinae Alcock, 1898 Actaeodes tomentosus (H. Milne Edwards, 1834) Sakai 1939 Chlorodiellinae Ng and Holthuis, 2007 Chlorodiella barbata (Borradaile, 1900) present study Chlorodiella cytherea (Dana, 1852) Miyake 1938 Chlorodiella nigra (Forskål, 1775) Horikawa 1940 Cyclodius taiwanensis sp. nov. present study Liocarpilodes harmsi (Balss, 1934) Hsueh et al. 2009 Liocarpilodes sp. present study Luniella scabriculus (Dana, 1852) Hsueh et al. 2009 Pilodius nigrocrinitus Stimpson, 1859 Hsueh et al. 2009 Etisinae Ortmann, 1893 Etisus frontalis (Dana, 1852) present study Etisus sp. A present study Etisus sp. B present study Euxanthinae Alcock, 1898 Psaumis cavipes (Dana, 1852) Sakai 1939 Liomerinae T. Sakai, 1976 Liomera bella (Dana, 1852) Suzuki 1985 Liomera rugata (H. Milne Edwards, 1834) Ho et al. 2000 Xanthinae MacLeay, 1838 Atergatis floridus (Linnaeus, 1767) Maki and Tsuchiya 1923 Leptodius sanguineus (H. Milne-Edwards, 1834) Parisi 1916 Lioxanthodes alcocki Calman, 1909 present study Macromedaeus crassimanus (A. Milne-Edwards, 1867) Ho et al. 2000 Macromedaeus quinquedentatus (Krauss, 1843) present study Macromedaeus sp. A present study Paraxanthias notatus (Dana, 1852) Lin 1949 Xanthias lamarckii (H. Milne-Edwards, 1834) Horikawa 1940 Zosiminae Alcock, 1898 Zozymodes pumilus (Hombron and Jacquinot, 1846) Hsueh et al. 2009 page 2 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan P2–P5 as ambulatory legs). The name of specimen collector was indicated only when the specimen was not collected by the first author. All specimens were deposited at the National Museum of Natural Science (NMNS), Republic of China. Fig. 1. Sampling locations (in closed circles) of the present study. N Table 2. Name and coordinate of collection sites Collection site Coordinates Jialulan 22°48.17'N 121°11.95'E Jihuei 23°06.87'N 121°24.21'E Linshanbi 25°17.12'N 121°30.33'E Longtou 22°00.24'N 121°35.63'E Shadao 21°54.71'N 120°50.83'E Shanfu 20°20.56'N 120°21.57'E Shihmen 25°17.84'N 121°34.23'E Shitiping 23°28.96'N 121°30.78'E Wanlitong 21°59.77'N 120°42.27'E Youzaihu 21°59.77'N 120°42.27'E RESULTS TAXONOMY Family Xanthidae MacLeay, 1838 Subfamily Actaeinae Alcock, 1898 Genus Actaeodes Dana, 1851 Actaeodes tomentosus (H. Milne Edwards, 1834) (Fig. 2A) Actaeodes tomentosus Heller 1861a: 9; 1861b: 32; A. Milne Edwards 1865: 262; Richters 1880: 145; Miers 1879: 486; Guinot 1967a: 553, 561; 1969: 237; 1971: 1072; 1976: 244, figs. 38 D, 41 C, pl. 15, fig. 1, 1a; Serène 1968: 79; 1977: 50; Serène 1984: 134, fig. 78, pl. XVIII A (for complete synonymy); Takeda and Hayashi 1973: 72; Serène et al. 1974: 22; Sakai 1976: 447, fig. 239; Peyrot-Clausade 1977a: 26; Ribes 1978: 126; Thomassin 1978: 64; Kensley 1981: 43; Ng et al. 2008: 195 [List]; Ng et al. 2017: 87 (for complete collection records from Taiwan). Material examined: 4 ♀, NMNS 8772-1–3, 6.9–12.4 × 4.6–8.0, Jihuei, Taitung County, 4–6 May 2005; 2 ♀, NMNS 8772-4, 7.6–10.7 × 4.8–6.0, Shanfu, Liuqiu Township, Pingtung County, 4 May 2007; 4 ♀, NMNS 8772-5, 3.2–4.5 × 2.0–2.6, Wanlitong, Pingtung County, 16 December 2007; 3 ♀, NMNS 8772-6, 7.7–8.2 × 4.9–5.3, Wanlitong, Pingtung County, 13 May 2009; 2 ♀, NMNS 8772-7, 4.5–10.4 × 2.9–6.6, Jihuei, Taitung County, 17 October 2009; 1 ♀, NMNS 87728, 5.5 × 3.1, Jihuei, Taitung County, 9 October 2010; 2 ♀, NMNS 8772-9, 3.8–4.2 × 2.6–2.7, Jihuei, Taitung County, 27 September 2014; 3 ♀, NMNS 8772-10, 3.4–8.0 × 2.3–6.5, Jihuei, Taitung County, 29 April 2017. Distribution: Indo-West Pacific; Red Sea; Hawaii Islands (Serène 1984). Remarks: Actaeodes tomentosus (H. Milne Edwards, 1834) (Fig. 2A) is commonly found in reef habitats in Taiwan. There are numerous reports noting the presence of this species in Taiwanese waters (Ng et al. 2017). Subfamily Chlorodiellinae Ng and Holthuis, 2007 Genus Chlorodiella Rathbun, 1897 Chlorodiella barbata (Borradaile, 1900) (Fig. 2C–G) Chlorodiella barbata Rathbun 1911: 225; Balss 1934: 515; 1938: 53; Ward 1932: 250; 1939: 10; 1942: 97; Tweedie 1950: 121; Holthuis 1953: 14; Barnard 1954: 98; Forest and Guinot 1961: 96, figs. 93, 94, 99, 100; Michel 1964: 23; Guinot 1967b: 262 [List]; Serène 1968: 81 [List]; 1984: 260, fig. 170, pl. XXXVI A (for complete synonymy); Takeda and Nunomura 1976: 74; Peyrot-Clausade 1977a: 26; 1977b: 213; 1989: 112; Chen and Lan 1978: 270, figs. 4, 7 (4–5), pl. 1, fig. 4; Ribes 1978: 126; page 3 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Fig. 2. Actaeodes tomentosus (H. Milne Edwards, 1834) (female, CW 6.9 mm; NMNS 8772-1), A; Psaumis cavipes (Dana, 1852) (female, CW 8.6 mm; NMNS 8772-45), B; Chlorodiella barbata (Borradaile, 1900) (male, CW 4.1 mm; NMNS 8772-11), C–G: A–C, habitus, dorsal view; D, right chela, external view; E, left chela, external view; F, G1, right, external view; G, G1, right, distal area, external view. Scale bars: A–B = 2.0 mm; C = 1.0 mm; D–E = 0.5 mm; F–G = 0.1 mm. page 4 of 38 Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Thomassin, 1978: 3, 64; Dai et al. 1986: 314, fig. 168 (1), pl. 45 (3) [Review]; Dai and Yang 1991: 339, fig. 168 (1), pl. 45 (3); Davie 2002: 518 [Review]; Ng et al. 2008: 196 [List]; Lasley et al. 2015: 171. Material examined: 1 ♂, NMNS 8772-11, 4.1 × 2.5, Wanlitong, Pingtung County, 13 May 2009. Distribution: Indo-West Pacific; French Polynesia (Serène 1984; Poupin 1996). Remarks: The morphology of the present specimen (Fig. 2C–G) matches key characters of Chlorodiella barbata (Borradaile, 1900) as described by Serène (1984: 257, fig. 170, pl. XXX VI A). Serène noted that this species can be easily distinguished from its congeners by the presence of a tuft of numerous setae on the external surface of the chelae at the articulation of the finger and a relatively simple, truncate tip of G1. This is the first report of this species from Taiwan. Chlorodiella cytherea (Dana, 1852) (Fig. 3A, B, D, E) Chlorodiella cytherea Holthuis 1953: 14; Forest and Guinot 1961: 95, figs. 90–92, 98a, b; Guinot 1962a: 238; 1964b: 70; 1967b: 262 (part) [List]; Michel 1964: 24; Serène 1968: 81 [List]; 1984: 259, fig. 169, pl. XXXVI C (for complete synonymy); Garth 1973: 320; Serène et al. 1976: 18; Takeda and Nunomura 1976: 74; Sakai 1976: 466, fig. 2, pl. 166; Takeda and Miyake 1976: 108; Takeda and Kurata 1977: 94; Peyrot-Clausade 1977a: 26; 1977b: 213; 1989: 112; Chen and Lan 1978: 270; figs. 5, 7 (1–3), pl. 2, fig. 5; Ribes 1978: 126; Thomassin 1978: 64; Dai et al. 1986: 316, pl. 45(6), fig. 169(4) [Review]; Titgen 1987: 107, fig. 1a– d; Holthuis 1953: 14; Peyrot-Clausade 1989: 112; Dai and Yang 1991: 340, pl. 45(6), fig. 169(4); DeFelice et al. 1998: 16; Ng et al. 2008: 197 [List]; Castro 2011: 87 [List]; Lasley et al. 2015: 171; Ng et al. 2017: 88 (for complete collection records from Taiwan). Material examined: 1 ♀, NMNS 8772-12, 5.7 × 3.7, Shanfu, Liuqiu Township, Pingtung County, 24 October 2008; 1 ♂ 3 ♀, NMNS 8772-13, 8.4–11.0 × 5.3–6.6, Wanlitong, Pingtung County, 13 May 2009; 1 ♀, NMNS 8772-14, 7.2 × 4.4, Wanlitong, Pingtung County, 13 November 2009; 2 ♀, NMNS 8772-15–16, 3.5–5.2 × 2.4–3.2, Shadao, Hengchun Township, Pingtung County, coll. H.-T. Hung, 16–17 October, 2020. Distribution: Indo-West Pacific; Red Sea; Hawaii Islands; French Polynesia (Serène 1984; Poupin 1996). Remark: The morphology of the present specimens (Fig. 3A, B, D, E) matches the description of Chlorodiella cytherea (Dana, 1852) (Dana 1852b: 213– 214). Ng et al. (2017: 87) cited Sasaki (1976) as the first report of Chl. cytherea from Taiwan. However, Serène (1984) noted Chl. laevissima, as reported by Miyake (1938), is a junior synonym of Chl. cytherea. Thus, Miyake (1938), rather than Sasaki (1976), should be considered the first report of this species from Taiwan. Chlorodiella nigra (Forskål, 1775) (Fig. 3C) Chlorodiella nigra Rathbun 1897: 157 [Nomenclature]; 1911: 225; 1923: 108; Grant and McCulloch 1906: 12; Balss 1924: 10; De Man 1929a: 1; 1929b: 4; McNeill and Ward 1930: 383; Montgomery 1931: 441; Ward 1932: 249; Gordon 1934: 50; Shen 1936: 67; Miyake 1936: 508; Sakai 1936: 166; 1939: 508, pl. 97, fig. 1; 1965: 150, pl. 75, fig. 2; 1976: 465, pl. 166, fig. 1; Chopra and Das 1937: 402, pl. 6, fig. 2; Ramadan 1936: 32; Monod 1938: 132; Barnard 1950: 213; 1955: 29, fig. 10; Holthuis 1953: 15; Guinot 1962a: 238; 1964a: 12; 1964b: 69; 1967b: 262 [List]; Forest and Guinot 1961: 95, figs. 87–89, 97a, b; Sankarankutty 1966a: 351; 1966b: 50; Michel 1964: 24; Serène 1968: 81 [List]; 1977: 51; 1984: 258–259, fig. 168, pl. XXXVI B (for complete synonymy); Serène et al. 1976: 18; Takeda and Nunomura 1976: 74; Takeda and Miyake 1976: 108; Peyrot-Clausade 1977a: 26; 1977b: 213; Chen and Lan 1978: 268, figs. 1, 7 (6–7), pl. 1, fig. 1; Ribes 1978: 126; Takeda 1978: 40; Kensley 1981: 44 [List]; Garth and Kim 1983: 687; Dai et al. 1986: 315, pl. 45(5), fig. 169(2) [Review]; Dai and Yang 1991: 339, pl. 45(5), fig. 169(2) [Review]; Davie 2002: 519 [List]; Ng et al. 2008: 197 [List]; Lasley et al. 2015: 171, fig. S4A; Ng et al. 2017: 88 (for complete collection records from Taiwan). Material examined: 1 ♀, NMNS 8772-17, 8.5 × 6.0, Linshanbi, Shihmen District, New Taipei City, 18 December 2011. Distribution: Indo-West Pacific; Hawaii Islands; French Polynesia (Serène 1984; Poupin 1996). Remarks: Chlorodiella nigra (Forskål, 1775) (Fig. 3C) is commonly found in reef habitats in Taiwan. Numerous reports have noted the presence of this species along the coasts of eastern and southern Taiwan (Ng et al. 2017). This study reports the occurrence of this species in northern Taiwan, where the annual surface seawater temperature in January is over 5°C lower than that of eastern and southern Taiwan (Central Weather Bureau 2023). Genus Cyclodius Dana, 1851 Cyclodius taiwanensis sp. nov. (Figs. 4A–H, 5A–D, 6A–D, 7A–F) urn:lsid:zoobank.org:act:9BC4D0FC-A342-413D-98EFFA819C794785 Material examined: Holotype, NMNS 8772-18, ♂, 8.9 × 6.2, Jihuei, Taitung County, 9 October 2010. Paratypes: 1 ♀, NMNS 8772-19, 6.6 × 4.2, Wanlitong, Pingtung County, 13 November 2009; 1 ♂, NMNS 8772-20, 4.8 × 3.3, Jihuei, Taitung County, 7 October 2010; 1 ♀, NMNS 8772-21, 4.3 × 2.7, Jihuei, Taitung County, 27 September 2014; 1 ♂ 1 ♀, NMNS 877222–23, 7.2–9.6 × 4.6–6.2, Jihuei, Taitung County, 28 April 2017. page 5 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Etymology: The name is derived from Taiwan, the island where the specimens were collected. Description: Holotype, carapace (Figs. 4A, B, 6A, B) transversely hexagonal, width about 1.44 length; dorsal surface granulate, covered with long and short simple light-colored setae; regions weakly defined. Front moderately convex, about 0.27 times carapace width, strongly deflexed ventrally, margin granulate; divided into two lobes by wide V-shaped notch, continuing posteriorly as shallow median groove on dorsal carapace. Anterolateral margin with anterolateral direct spinose teeth, separated by concave gaps; tooth 1 with 2 emergent spines, larger than supraorbital tooth, tooth 2 and 3 subequal in size, both with 2 large and 1 small anterolateral pointed spine, tooth 4 with 1 large spine and secondary spines. Posterolateral margin longer than anterolateral margin, slightly convex medially. Orbits (Figs. 4A–C, 6A, B) suboval, margins denticulate, supraorbital margin with 2 small notches medially; inner pre-frontal supraorbital and exorbital tooth weakly developed. Eyes well developed, eyestalks short, stout, corneas large. Antennular fossae transversely oval; antennules folding transversely. Basal antennal article with small lateral flange, entering less than halfway into orbital hiatus. Antennae freely entering orbital hiatus. Third maxillipeds (Figs. 4C, D, 7A) subrectangular, length to width ratio about 1.55; palp tapering distally, articles subcylindrical; merus subquadrate, length to width ratio about 0.55, anterolateral angle concave, anterior margin sinuous and granulate, few stout and simple setae; external surface with scattered granules; ischium subrectangular, about 2.58 times longer than merus, sulcate submedially, mesial margin cristate, serrated, lined with submarginal setae; exopod stout, external margin straight, internal margin denticulate, Fig. 3. Chlorodiella cytherea (Dana, 1852) (female, CW 7.2 mm; NMNS 8772-14), A; Chlorodiella cytherea (Dana, 1852) (male, CW 10.5 mm; NMNS 8772-13(1)), B, D, E; Chlorodiella nigra (Forskål, 1775) (female, CW 8.5 mm; NMNS 8772-17), C: A–C, habitus, dorsal view; D, G1, right, internal view; E, G1 distal area, right, internal view. Scale bars: A–C = 2.0 mm; D = 0.5 mm; E = 0.01 mm. page 6 of 38 Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan tapering slightly toward distal end, distal end concave. Thoracic sternum (Figs. 4G, 7B) margins cristate; sternites 1, 2 fused with low of transverse granules on suture; sternites 2, 3 separated by narrow, deep suture, margins smooth; sternites 3, 4 mostly fused, with remnants of suture only at lateral edges; sternite 4 with prominent median longitudinal line extending through entire exposed length, lateral margins slightly convex; sutures 4/5, 5/6 joining toward median longitudinal axis of thoracic sternum; small, central, triangular, noncalcified area present between sternites 6, 7 within sternopleonal cavity; press-button on anterior half of sternite 5. Chelipeds (Figs. 4E, F, 6C) subequal, moderately robust, external surfaces granulate covered with long and short simple, light-colored setae. Meri moderate long, distal end extending slightly beyond carapace anterolateral margin in dorsal view, upper margin unarmed, lower margin denticulate. Carpi rhombicshaped, covered with rows of granules. Palm external surface covered with row of granules. Fingers thick, tips hemi-cupuliform, pigmentation restricted to fingers; dactylus gently curved toward distal end, dorsal margin with 2 rows of granules proximally, 3 large teeth on cutting edge; pollex straight proximally, slightly curved upward distally, 3 or 4 large teeth on cutting edge. Ambulatory legs (Figs. 4A, H, 6D) flattened, broad, moderate in length, P3, P4 longest, P5 shortest; surfaces entirely granulate, covered with long and short simple, light-colored setae; anterior margin of meri, carpi, propodi, dactyli denticulate; posterior margin of meri, propodi, dactyli denticulate; dactyli single-tipped. P5 merus subrectangular, median length about 1.86 times greatest width; carpus curved, distal end distinctly wider than proximal end, median length about 1.11 times greatest width; propodus subrectangular, median length about 0.91 times greatest width; dactylus longer than propodus, stout proximally, tapering distally, terminating in robust, short chitinous claw with length 1.43 times greatest width. Pleon (Figs. 4G, 7C) moderate long relative to thoracic sternum, tip of telson reaching level slightly lower to sternal condyles of P1 coxae; somite 1 trapezoidal with anterior margin strongly concave, somite 2 trapezoidal, as wide as somite 1 with anterior margin strongly concave and posterior margin strongly convex; somites 3–5 fused with residue sutures reaching 1/3 to median line, base of somite 3 widest, distal somites progressively narrower, combined lateral margin gently concave; somite 6 subquadrate, width about 1.56 times length, anterior margin slightly concave, lateral margins and posterior slightly sinuous; telson subtriangular, angles round, basal width about 1.71 times median length. G1 (Figs. 5A, B, 7D–F) moderate in length, stout, distal half acutely bent lateroventrally with 5 long and 6–8 short, simple, subdistal setae, numerous short spines; distal tip lobe ovate with round-tipped. G2 sigmoidal in shape, about one-third length of G1. Female morphology: The immature female (Figs. 5C, D, 7G) is morphologically similar to the male in most body parts, except for the sexual characteristics. The pleon of the female is generally wider and more elongate-oval in shape compared to that of the male. The vulvae are oval, lack an operculum, and are located on the mesial fourth of sternite 5. Distribution: Known only from type locality and Wanlitong, Pingtung County. Remarks: The genus Cyclodius Dana, 1851 was synonymized as a junior name of Phymodius by A. Milne-Edwards (1863) but was resurrected by Davie (2002) and had been used since (Lasley et al. 2015: 173). The current recognized species within the genus include: Cyclodius drachi (Guinot, 1964), Cyc. granulatus (Targioni-Tozzetti, 1877), Cyc. granulosus de Man, 1888; Cyc. nitidus (Dana, 1852), Cyc. obscurus (Hombron and Jacquinot, 1846), Cyc. paumotensis (Rathbun, 1907), Cyc. perlatus (Nobili, 1905), and Cyc. ungulatus (H. Milne Edwards, 1834) (Lasley et al. 2015: 173). The present study introduces a new member to the genus. The present species exhibits a basal antennal article (Figs. 4C, 6B) similar to that of Cyclodius Dana, 1851, where the basal antennal article has a distolateral extension occluding less than half the length of the orbital hiatus (Serène 1984: 233; Ng and Yang 1998: 1693, fig. 5B; Clark and Ng 1999: 354, 359, fig. 6C, tabl. 1; Lai et al. 2011: 433; Lasley et al. 2015: 173, fig. S5B, D). Among known Cyclodius species, only Cyc. paumotensis (Rathbun, 1907) shares the characteristic of having the carapace and external surfaces of chelipeds covered in long and short simple, light-colored setae (Figs. 4A, B. E, F, 5C; Serène 1984: 233; Clark and Galil 1993: 1143, figs. 35B, 43A; Lasley et al. 2015: 173, fig. S1C). However, Cyc. taiwanensis sp. nov. can be distinguished from Cyc. paumotensis by: 1) weakly defined carapace regions (versus well-defined) (Figs. 4A, B, 5C; Serène 1984: 241, pl. XXXIII D; Clark and Galil 1993: 1145, fig. 35B; Lasley et al. 2015: 173, fig. S1C); 2) an anterolateral margin without apical or accessary spines (versus with apical or accessory spines) (Figs. 4A, B, 5C; Serène 1984: 241, fig. 143d; Clark and Galil 1993: 1145, fig. 10A, 35B; Lasley et al. 2015: 173, fig. S1C); 3) a greater basal width to median length ratio of the 6th somite and telson (1.63 and 1.80 versus 1.34 and 1.34, respectively) (Figs. 4G, 7C; cf. Rathbun 1907: 52, pl. 2b); and 4) the G1 acutely bent subdistally with a round-tipped distal lobe (versus gently curved page 7 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Fig. 4. Cyclodius taiwanensis sp. nov., holotype (male, CW 8.9 mm; NMNS 8772-18): A, habitus, dorsal view; B, carapace, dorsal view; C, habitus, frontal view; D, 3rd maxilliped; E, right chela, external view; F, left chela, external view; G, thoracic sternum and pleon; H, P5, right, dorsal view. Scale bars: A = 2.0 mm; B–H = 1.0 mm. page 8 of 38 Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Fig. 5. Cyclodius taiwanensis sp. nov., holotype (male, CW 8.9 mm; NMNS 8772-18), A, B; paratype (female, CW 7.2 mm; NMNS 8772-23), C, D: A, G1, external view; B, G1 distal area, internal view; C, carapace, dorsal view; D, thoracic sternum and pleon. Scale bars: A, D = 0.5 mm; B = 0.01 mm; C = 1.0 mm. subdistally with a sharp distal lobe) (Figs. 5A, B, 7D–F; Serène 1984: 241, fig. 145; Clark and Galil 1993: 1143, fig. 10D–G; Lasley et al. 2015: 173, fig. S3B). The G1 structure is considered a reliable distinguishing characteristic among Cyclodius species (Lasley et al. 2015: 173). Although the G1 form in Cyc. taiwanensis sp. nov. is unique within the genus, it shows some resemblance to that of Pilodius luomi Serène, 1971 (= Pilodius miersi (Ward, 1936)), as described by Serène (1971: 914–914) (Figs. 5A, B, 7D–F; Serène and Van Luom 1959: 307, fig. 2E, F; Serène 1971: 58; Serène 1984: 245, figs. 153–158; Clark and Galil 1993: page 9 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Genus Pilodius Dana, 1851 Pilodius nigrocrinitus Stimpson, 1859 (Fig. 11A–E) Pilodius nigrocrinitus Stimpson 1859: 34; 1907: 58, pl. 7, fig. la, b; Balss 1938: 57 [List]; Forest and Guinot 1961: 89 [List]; Sakai 1965: 148, pl. 73, fig. 5; 1976: pl. 164, fig. 2, text-figs. 248a–b; Serène 1968: 80 [List]; Serène 1984: 235 [Key]; Dai et al. 1986: 307, pl. 43(5), text-fig. 166(2); McNeill 1968: 73 (part); Takeda and Nunomura 1976: 73; Dai and Yang 1991: 330, pl. 43(5), text-fig. 166(2); Clark and Galil 1993: 1139, figs. 9A–G, 24, 35A, 42B, C (for complete synonymy); Ng et al. 2008: 197 [List]; Lasley et al. 2015: 172, fig. S4B. Material examined: 1 ♂, NMNS 8772-38, 8.4 × 5.6, Shihmen, New Taipei City, 3 October 2008; 1 ♀, NMNS 8772-39, 5.2 × 3.4, Jihuei, Taitung County, 13 December 2012. Distribution: Indo-West Pacific; Pacific Ocean (Clark and Galil 1993: 1140–1142). Remarks: The morphology of the present specimens (Fig. 11A–E) largely aligns with the description of P. nigrocrinitus Stimpson, 1859 provided by Clark and Galil (1993: 1139–1140, figs. 9A–G, 35A, 42B–C). Notably, it features an enlarged distolateral flange on the basal antennal article that completely blocks the orbital hiatus and moderately stout G1 with numerous stout subdistal setae and a hooked apical Fig. 10. Luniella scabricula (Dana, 1852) (male, CW 4.4 mm; NMNS 8772-37): A, habitus, dorsal view; B, G1 of male, right, external view; C, close-up of G1 distal area, right, external view; E, G1 of male, right, internal view; F, close-up of G1 distal area, right, internal view. Scale bars: A = 2.0 mm; B = 0.5 mm; C = 0.05 mm. page 16 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Fig. 11. Pilodius nigrocrinitus Stimpson, 1859 (male, CW 8.5 mm; NMNS 8772-38): A, habitus, dorsal view; B, habitus, anterior view; C, right chela, external view; D, left chela, external view; E, G1, right, internal view; F, G1, right, distal area, internal view; G, G1, right, apex area, internal view. Scale bars: A = 2.0 mm; B = 1.0 mm; C, D = 0.5 mm; E = 0.2 mm; F, G = 0.05 mm. page 17 of 38 Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Fig. 12. Etisus frontalis (Dana, 1852) (female, CW 8.7 mm; NMNS 8772-40): A, habitus, dorsal view; B, right chela, external view. Scale bars: A = 2.0 mm; B = 0.5 mm. lobe. This is the first recorded occurrence of this species in Taiwan. Subfamily Etisinae Ortmann, 1893 Genus Etisus H. Milne Edwards, 1834 Etisus frontalis (Dana, 1852) (Fig. 12A, B) Etisus frontalis Guinot 1964b: 50–56, figs. 23, 25–27, 31a–c, 35, pl. V, fig. 2; Serène 1968: 80; 1984: 229, fig. 139, pl. XXXI E (for complete synonymy); Ng et al. 2008: 198 [List]. Material examined: 1 ♀, NMNS 8772-40, 8.7 × 6.3, Shanfu, Liuqiu Township, Pingtung County, 18 November 2017. Distribution: Aldbra (Seychelles); Hikueru (French Polynesia); Jolo Sea (Philippines) (Guinot 1964); Xiao Liuqiu Island, southwestern Taiwan. Remarks: The morphology of the present specimen (Fig. 12A, B) matches description of E. frontalis (Dana, 1852), characterized by similarly sized submedian and lateral lobules of the front and the black coloration of the fixed finger of the chelipeds extending slightly onto the palm (Guinot 1964b: 51, 53, figs. 23, 26–27; Serène 1984: 224, pl. XXXI E). This species is reported for the first time from Taiwan. Etisus sp. A (Fig. 13A–H) Material examined: 1 ♀, NMNS 8772-41, 5.2 × 3.6, Jialulan, Taitung County, coll. Y.-W. Tzeng, 23 July 2013. Description: Carapace (Fig. 13A–C) transversely ovate, width to length ratio about 1.45, dorsal area slightly convex transversely, longitudinally; dorsal surface well covered by microscopic granules, except 3M, 4M, L, P, R regions, stout long setae scattered at anterior regions and lined with grooves of posterior regions; regions well defined, divided by wide, deep grooves; subhepatic, pterygostomial regions granulate, long setae scattered. Front strongly advanced, about 0.33 times as long as carapace width, slightly deflexed ventrally, margin granulate, outer angles well marked and separated by V-shaped notch from orbital rim; divided into 2 lobes by shallow V-shaped notch, continuing posteriorly as deep median groove on dorsal carapace, each lobe with 2 subequal lobules. Anterolateral margin convex, granulate, divided into 4 lobes, separated from each other by wide V-shaped notches; first lobe highest, gradually reducing in height thereafter; third lobe base widest, anterior margin slightly shorter than posterior; fourth lobe smallest, posterior margin continuous with carapace posterolateral margin. Posterolateral margin slightly longer than anterolateral margin, central region slightly concave. Orbits (Fig. 13A–C) suboval, margins granulate, continuous; inner pre-supraorbital tooth prominent, supraorbital margin with low tooth adjacent to exorbital tooth, separated from pre-supraorbital tooth and from exorbital tooth by V-shaped notch; exorbital tooth sharply triangular. Eyes well developed, eyestalks short, stout, corneas large. Antennular fossae transversely oval; antennules folding transversely. Basal article of antenna short, triangular; flagellum freely entering orbital hiatus, long, tip far exceeding exorbital tooth. Third maxillipeds (Fig. 13D) subrectangular, length to greatest width ratio about 2.22; palp tapering distally, articles subcylindrical; merus subquadrate, page 18 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Fig. 13. Etisus sp. A (female, CW 5.2 mm; NMNS 8772-41): A, habitus, dorsal view; B, carapace, dorsal view; C, habitus, anterior view; D, 3rd maxillipeds; E, left chela, internal view; F, left chela, external view, arrow pointing acetabulum-like structure; G, P5, left, dorsal view; H, pleon. Scale bars: A = 1.0 mm; B–H = 0.5 mm. page 19 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan length to greatest width ratio about 0.67, anterolateral angle rounded, slightly projecting, anterior margin straight, cristate, granulate, stout setae scattered, external surface with patched granules, long, thin setae scattered; ischium subrectangular, about 1.83 times longer than merus, sulcate submedially, mesial margin cristate, serrated, lined with submarginal setae, external surface scattered with long setae; exopod stout, margins slightly convex, tapering slightly toward distal end, distal end slightly convex. Thoracic sternum margins cristate; sternites 1, 2 fused, external surface smooth; sternites 2, 3 and 3, 4 separated by deep and shallow sutures, respectively; sternite 4 with row of long setae at anterior margin, lateral margins clearly convex; sutures 4/5, 5/6 joining toward median longitudinal axis of thoracic sternum; vulvae oval, without operculum, located mesial third of sternite 5. Left cheliped (Fig. 13E, F) moderately robust. Meri moderate long, distal end clearly extending beyond carapace anterolateral margin in dorsal view. Carpi dorsal margin granulate, subdistal end with large tubercle, internal distal angle with one row of 3 small spines. Palm dorsal margin granulate, with small tubercle proximally, external surface granules compacted, forming perpendicular lines or stripes, proximal end of lower margin with large acetabulumlike structure, distal end of lower margin with shallow groove extending anteriorly to middle of pollex. Finger thick, tips rounded; dactylus brownish in alcohol except distal end, dorsal margin with granulate submargin crests, forming longitudinal groove toward medial region of dorsal margin, distal area moderately recurved, external surface lower submargin with longitudinal shallow groove, extending two-thirds of dactylus from proximal end, three large teeth on proximal end of cutting edge, 2 thin, blade-like low teeth on distal end of cutting edge; pollex beige in alcohol, proximal end of cutting edge with 2 small, low teeth and 3 larger blunt teeth, distal end with 2 medium-sized low teeth. Ambulatory legs (Fig. 13G) flattened, broad, moderate in length, P2, P3 longest, coxa-to-dactylus length about 0.94 times carapace width, P5 shortest, coxa-to-dactylus length about 0.81 times carapace width; surfaces entirely smooth, anterior margin of meri spinose, anterior margin of carpi, propodi, dactyli granulate, anterior submargin of meri, carpi, propodi, dactyli lined with many short and long setae, posterior margin of meri, carpi smooth, submargin lined with short and long setae, posterior margins of propodi denticulate, submargin lined with short and long setae, posterior margins of dactyli spinose, with single large tubercle posterior to chitinous claw, single-tipped. P5 merus subrectangular, median length about 1.54 times greatest width; carpus curved, distal end distinctly wider than proximal end, median length about 1.60 times greatest width; propodus subrectangular, median length about as long as greatest width; dactylus longer than propodus, stout proximally, tapering distally, terminating in sharp, short chitinous claw with length about 1.86 times greatest width. Pleon (Fig. 13H) moderate long relative to thoracic sternum, tip of telson reaching anterior margin of sternite 4; somites 1, 2 trapezoidal, much wider than long; somites 3–5 subrectangular, not fused, subequal in width, combined lateral margin gently convex; somite 6 subrectangular, much wider than long, angles rounded, lateral margins convex; telson subtriangular, angles rounded, basal width about 1.5 times median length. Distribution: Known only from the coast of East Taiwan. Remarks: Interestingly, Etisus sp. A possesses an acetabulum-like structure on external, lower proximal margin of the propodus of the left chela (Fig. 13F). This feature might be a scar from a previous injury. The morphology of Etisus sp. A is somewhat resembles that of E. anaglyptus (H. Milne Edwards, 1834), which has subquadrate frontal lobes extending beyond the supraorbital angles and separated by a deep V-shaped notch (Fig. 13A, B; A. Milne-Edwards 1873: 80 (4), pl. 12 (1), fig. 3; Serène 1984: 227–228, pl. XXXII A, E). However, Etisus sp. A differs from E. anaglyptus in the following ways: 1) frontal lobes extending well beyond the supraorbital angles (versus slightly beyond); 2) a greater fronto-orbital to carapace width ratio (0.33 versus 0.19); 3) anterolateral tooth N, T and S (2nd to 4th) with blunt-tipped (versus acute tips); and 4) outer edge of ambulatory legs covered in granules (versus strong spines) (Fig. 13A, B, G; Serène 1984: 228, pl. XXXII A). More adult male and female specimens are needed to determine the true identity of this distinct Etisus species. The current description is based on a single juvenile female specimen, and it remains uncertain whether there are variations between sexes or ontogenetic morphological changes. Etisus sp. B (Figs. 14A–H, 15A–H, 16A–F) Material Examined: 1 ♀, NMNS 8772-42, 5.3 × 3.8, Shanfu, Liuqiu Township, Pingtung County, 4 May 2007; 1 ♂, NMNS 8772-43, 5.7 × 4.1, Shanfu, Liuqiu Township, Pingtung County, 24 October 2008; 1 ♀, NMNS 8772-44, 4.1 × 2.9, Shanfu, Liuqiu Township, Pingtung County, 5 November 2011. Description: Carapace (Fig. 14A, C, E) transversely ovate, width to length ratio about 1.38, dorsal area slightly convex transversely, longitudinally; dorsal page 20 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan surface well covered by microscopic granules, short setae scattered at anterior regions and level with grooves at posterior regions; regions moderately divided by shallow grooves; subhepatic, pterygostomial regions granulate, glabrous. Front moderately advanced, about 0.41 times as long as carapace width, strongly deflexed ventrally, margin granulate, outer angles well marked, separated by V-shaped notch from orbital rim; divided into two lobes by deep V-shaped notch, continuing posteriorly as shallow median groove on dorsal carapace. Anterolateral margin convex, granulate, divided into 4 or 5 lobes, separated from each other by V-shaped or U-shaped notches with intercalated denticles; right anterolateral margin with 5 lobes, first lobe very low, feebly demarcated from second lobe; second lobe low; third lobe base widest, apex pointing anteriorly, anterior margin much shorter than posterior; fourth lobe similar to third but smaller; fifth lobe triangular, posterior margin continuous with carapace posterolateral margin; left anterolateral margin with 4 lobe, all lobes in equilateral triangle, apex of lobes 1–3 pointed anterolaterally, fourth lobe pointing laterally. Posterolateral margin slightly longer than anterolateral margin, with central region slightly concave. Orbits (Fig. 14A, C, E) suboval, margins granulate; inner pre-frontal supraorbital and exorbital tooth weakly developed; supraorbital margin with one closed fissure. Eyes well developed, eyestalks short, stout, corneas large. Antennular fossae transversely oval; antennules folding transversely. Basal article of antenna short, subrectangular; flagellum freely entering orbital hiatus, short, tip slightly exceeding exorbital tooth. Third maxillipeds (Fig. 16B, D) subrectangular, length to greatest width ratio about 2.05; palp tapering distally, articles subcylindrical; merus subquadrate, length to greatest width ratio about 0.83, anterolateral angle rounded, slightly projecting, anterior margin slightly sinuous, cristate and granulate, stout and thin setae scattered, external surface well covered with granules; ischium subrectangular, about 1.85 times longer than merus, sulcate submedially, mesial margin cristate, serrated, lined with submarginal setae; exopod stout, margins slightly convex, inner margin cristate, tapering slightly toward distal end, distal end slightly concave. Thoracic sternum (Fig. 14G) margins cristate; sternites 1, 2 fused, external surface smooth; sternites 2, 3 and 3, 4 separated by deep and shallow sutures, respectively; sternite 4 with prominent median longitudinal line extending through half of exposed length, lateral margins slightly convex; median longitudinal line interrupted on sternite 4 within anterior region of sternopleonal cavity, continued at posterior limit of sternite 4, absent in sternites 5, 6, continued in sternites 7, 8 without interruption; sutures 4/5, 5/6 joining toward median longitudinal axis of thoracic sternum; vulvae oval, without operculum, located mesial third of sternite 5; small, central, triangular, non-calcified area present between sternites 6, 7 within sternopleonal cavity; press-button on anterior half of sternite 5. Chelipeds (Figs. 14A, 15A–D) subequal, moderately robust, external surface almost fully granulate, except distal areas of fingers. Meri moderate long, distal end extending slightly beyond carapace anterolateral margin in dorsal view, dorsal margin granulates, with triangular projection distally. Carpi dorsal margin granulate, with 2 large, triangular tubercles subdistally. Palm dorsal margin granulate, granules raised forming as crest, with two triangular tubercles sub-proximally and 1 rounded tubercle distally, external surface granules compacted, forming reticulated pattern, or arranged in longitudinal rows. Fingers thick, tips hemi-cupuliform; dactylus dorsal margin with 2 parallel crests, forming groove extending toward subdistal end, proximal end with triangular tubercle, distal area strongly deflexed, meeting only at tip with pollex, leaving large gap between fingers, 3 large teeth on proximal end of cutting edge; pollex distal area slightly deflexed, 1 small, 2 large teeth on proximal end of outer cutting edge, 1 small tooth on proximal end of inner cutting edge. Ambulatory legs (Figs. 14A, 16A) flattened, broad, moderate in length, P3, P4 longest, coxa-todactylus length about 0.91 times carapace width, P5 shortest, coxa-to-dactylus length about 0.71 times carapace width; surfaces entirely smooth; anterior margin of meri spinose, submargin lined with short and long setae, carpi, propodi, dactyli denticulate, submargin lined with short and long setae; posterior margin of meri, submargin lined with long setae, carpi, propodi smooth, without setae, dactyli spinose, with single medium-sized spine posterior to chitinous claw, singletipped. P5 merus subrectangular, median length about 1.72 times greatest width; carpus curved, distal end distinctly wider than proximal end, median length about 1.25 times greatest width; propodus subrectangular, median length about 1.19 times greatest width; dactylus longer than propodus, stout proximally, tapering distally, terminating in sharp, short, slender chitinous claw with length about 2.0 times greatest width. Pleon (Fig. 14G) moderate long relative to thoracic sternum, tip of telson reaching level to anterior sternal condyles of P2 coxae; somites 1, 2 trapezoidal, much wider than long; somites 3–5 fused, base subequal in width, combined lateral margin straight; somite 6 subquadrate, slightly longer than wide, lateral margins page 21 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Fig. 14. Etisus sp. B, male (CW 5.8 mm; NMNS 8772-42), A, C, E, G; female (CW 4.1 mm; NMNS 8772-44), F, G: A, B, habitus, dorsal view; C, D, carapace, dorsal view; E, F, habitus, anterior view; G, male pleon; H, female pleon. Scale bars: A, C–D = 1.0 mm; B = 2.0 mm; E–H = 0.5 mm. page 22 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Fig. 15. Etisus sp. B, male (CW 5.8 mm; NMNS 8772-42), A–D; female (CW 4.1 mm; NMNS 8772-44), E–H: A, E, right chela, external view; B, F, right chela, internal view; C, G, left chela, external view; D, H, left chela, internal view. Arrows indicate the second row of tooth on the proximal end of the cutting edge’s internal margin. Scale bars: A–H = 0.5 mm. page 23 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Fig. 16. Etisus sp. B (male, CW 5.8 mm; NMNS 8772-42), A, B, D–F; paratype (female, CW 4.1 mm; NMNS 8772-44), C: A, P5, left, dorsal view; B, C, right 3rd maxilliped; D, anterior area of the right 3rd maxilliped; E, G1, right, external view; F, G1, right, distal area, external view. Scale bars: A– D = 0.2 mm; E = 0.5 mm; F = 0.05 mm. straight; telson subtriangular, angles rounded, basal width about as long as median length. Female morphology: The female (Figs. 14B, D, F, H, 15E–H, 16C) is morphologically similar to the male in most body parts, with differences in the carapace, sexual characters, and chelipeds. The female’s carapace is less concave compared to that of the male. The front of the female shows only traces of submedian lobules and is slightly retreated laterally, whereas the male has broader submedian lobules that are moderately retreated. The female's pleon is generally wider and more triangular than the male’s. Additionally, the sternopleonal cavity of the female is wider but shallower. The vulvae are oval and located on the mesial third of sternite 5. The female’s chelipeds are less robust and nearly equal in size, in contrast to the male’s, which are robust and subequal. The dactylus of both chelae in the female is slightly recurved distally, leaving a smaller gap when close, whereas in the male, it is strongly recurved and leaves a larger gap. Distribution: Known only from the Liuqiu Island, offshore from southwestern Taiwan. Remarks: Of the known congeners, Etisus sp. B shares morphological similarities with E. demani Odhner, 1925 and E. odhneri Takeda, 1971, notably in the following features: 1) a bi-lobed front separated by a median V-shaped notch with frontal lobes being slightly sinuous and fringes with pearly granules; 2) intercalated denticles between the anterolateral lobes of the carapace; and 3) strongly recurved distal fingers of chelipeds (Figs. 14A–D, 15A–D; Gordon 1941: 135–136, fig. 9c; Guinot 1964b: 51, 53, figs. 19, pl. VI, fig. 1; Takeda 1971: 193– 195, pl. 3, figs. 1–2; Serène 1984: 219, 223). However, Etisus sp. B can be distinguished from E. demani by the page 24 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan following: 1) a smaller carapace width/length ratio (1.38 versus 1.46–1.48) (Fig. 14A–D; Guinot 1964b: 51, fig. 19, pl. VI, fig. 1); 2) a single-rimmed front fringed with one row of pearly granules (versus double-rimmed with two rows of pearly granules) (Fig. 14A–D; Gordon 1941: 134, fig. 9d); 3) a granulate supraorbital margin with one fissure (versus smooth and with two fissures) (Fig. 14C–D; Gordon 1941: 134, fig. 9d; Guinot 1964b: 51, figs. 19, pl. VI, fig. 1); 4) a shallow, longitudinal groove dividing the middle of the 3M region in males (versus undivided) (Fig. 14A, C; Guinot 1964b: 51, figs. 19, pl. VI, fig. 1); 5) three uneven-sized teeth on the proximal half of the major chela’s dactylus cutting edge (versus two) (Fig. 15A–H; Gordon 1941: 134, fig. 9c); 6) two rows of teeth on the proximal cutting edge of the major chela’s pollex, with the outer and inner rows featuring three uneven conical teeth and one small teeth, respectively (versus with one row of one large and several minute teeth) (Fig. 15B, D, F, H; Gordon 1941: 134, fig. 9c); 7) a mosaic of granules on upper region and two rows of small conical granules on lower region of the minor chela’s palm (versus smooth) (Fig. 15C; Gordon 1941: 134, fig. 9c); 8) conical granules on the outer margins of the fourth ambulatory leg (versus strong spines) and a smooth inner margin on the fourth leg’s merus (versus spines) (Fig. 16A; Gordon 1941: 134, fig. 9a); 9) a smaller dactylus width/length ratio of the fourth ambulatory leg (0.33 versus 0.43) (Fig. 16A; Gordon 1941: 134, fig. 9a); 10) a smaller ischium width/length ratio of the third maxilliped (1.13 versus 1.48) (Fig. 16B–D; Guinot 1964b: 53, fig. 24, pl. VI, fig. 1); 11) a fully granulated outer surface of the third maxilliped’s merus and palp (versus smooth) (Fig. 16B– D; Guinot 1964b: 53, fig. 24, pl. VI, fig. 1); and 12) a strongly curved posteroventrally G1 distal part and subapex with eight short, stout setae (versus moderately curved with five long and two short setae) (Fig. 16E, F; Gordon 1941: 135, fig. 10d; Takeda 1971: 192, fig. 3C, D; Serène 1984: 222, fig. 140). Etisus sp. B differs from E. odhneri by: 1) broader submedian lobules on the front, single-rimmed with one row of pearly granules (versus feeble submedian lobules and double-rimmed with two rows) (Fig. 14A–D; Takeda 1971: 193, 209, pl. 3); 2) a divided middle 3M region by a shallow, longitudinal groove (versus undivided) (Fig. 14C; Takeda 1971: 193, 209, pl. 3, fig. 1); 3) a granulate supraorbital margin with one fissure (versus with two notches) (Fig. 15A–H; Takeda 1971: 193, 209, pl. 3, fig. 1); 4) three uneven teeth on the proximal cutting edge of the major chela’s dactylus (versus two) (Fig. 15A–H; Takeda 1971: 194, 209, pl. 3, fig. 2); 5) two rows of teeth on the major chela’s pollex, with the outer and inner rows having three uneven sized conical teeth and one small teeth (versus one row and four uneven teeth) (Fig. 15B, D, F, H; Takeda 1971: 194, 209, pl. 3, fig. 2); and 6) a strongly curved posteroventrally G1 distal area and a spatulate apex (versus moderately curved) (Fig. 16E, F; Takeda 1971: 192, fig. 3E–F; Serène 1984: 222, fig. 141). The described characteristics of Etisus sp. B are based on juvenile specimens, leaving the possibility of ontogenetic morphological changes as the species matures. Subfamily Euxanthinae Alcock, 1898 Genus Psaumis Kossmann, 1877 Psaumis cavipes (Dana, 1852) (Fig. 2B) Psaumis cavipes Serène 1984: 129–130, fig. 76, pl. XVIII F (for complete synonymy); Ng et al. 2008: 196 [List]; Ng et al. 2017: 87 (for complete collection records from Taiwan). Material examined: 1 ♂ 1 ♀, NMNS 877245–46, 3.8–5.1 × 2.3–3.3, Shanfu, Liuqiu Township, Pingtung County, 3–4 May 2007; 1 ♂, NMNS 8772-47, 5.8 × 3.5, Shanfu, Liuqiu Township, Pingtung County, 24 October 2008; 1 ♀, NMNS 8772-48, 8.5 × 5.4, Wanlitong, Pingtung County, 13 November 2009. Distribution: Indo-West Pacific; Fiji and Samoa (Dana 1852b; Serène 1984). Remarks: Psaumis Kossmann, 1877 was previously classified within the subfamily Actaeinae (Serène 1984: 92–94). However, Lai et al. (2011) proposed that this genus belongs to the subfamily Euxanthinae Alcock, 1898 based on both morphological and molecular evidence. Serène (1984: 129) reinstated the genus, following discussions on the identification of A. cavipes (Dana, 1852) by Guinot (1976: 203). The genus is a small taxonomic group represented by only two species: P. cavipes (Dana, 1852) (type locality: Fiji and Samoa) and P. fossulata (Girard, 1859) (type locality: Red Sea) (Serène 1984). While Serène (1984: 130) synonymized P. fossulata as junior name of P. cavipes, Ng et al. (2008) considered P. fossulata as a valid species. Alcock (1898: 148) distinguished Actaea fossulata (Girard, 1859) (= P. fossulata) (collection location: Great Coco Island and East Island, Andamans) from P. cavipes based on differences in the morphology of the front projections, carapace lobes, chelipeds, and ambulatory legs. The morphology of the current species (Fig. 2B) matches with diagnosis features of Psaumis cavipes, which include numerous small cavities on the dorsal carapace and ambulatory legs, and three distinct cavities on the suborbital and subhepatic regions (Serène 1984: 129). page 25 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Genus Paraxanthias Odhner, 1925 Paraxanthias notatus (Dana, 1852) (Fig. 17H) Paraxanthias notatus Odhner 1925: 84; Balss 1938: 51; Sakai 1939: 470, 1965: 142, pl. 71, fig. 3, 1976: 430–43, pl. 155, fig. 3; Edmondson 1946: 291, fig. 177e; Guinot 1964b: 30, 1968: 718, fig. 47; Dai et al. 1986: 277, fig. 156B(2), pl. 38(4); Dai and Yang 1991: 299, fig. 156B(2), pl. 38(4) (for complete synonymy); Ng et al. 2008: 204 [List]; Ng et al. 2017: 94 (for complete collection records from Taiwan). Material examined: 2 ♂, NMNS 8772-61, 8.8–9.8 × 5.9–6.5, Shadao, Hengchun Township, Pingtung County, coll. H.-T. Hung, 17 October, 2020. Distribution: Indo-Pacific (Dai and Yang 1991). Remarks: The morphology of the present specimen (Fig. 17H) aligns with the description of Paraxanthias notatus (Dana, 1852) provided by Dai and Yang (1991: 299, pl. 38 (4)). Collection records from Taiwan suggest that the distribution of this species is predominantly confined to the southern tip of Taiwan and nearby offshore islands (Ng et al. 2017). Genus Xanthias Rathbun, 1897 Xanthias lamarckii (H. Milne Edwards, 1834) (Fig. 20A) Xanthias lamarckii Serène 1984: 195–196, fig. 112, pl. XXVII B (for complete synonymy); Ng et al. 2008: 204 [List]; Ng et al. 2017: 94 (for complete collection records from Taiwan). Material examined: 1 ♀, NMNS 8772-62, 9.2 × 5.2, Shanfu, Liuqiu Township, Pingtung County, 3 May 2007; 1 ♀, NMNS 8772-63, 9.2 × 5.2, Shanfu, Liuqiu Township, Pingtung County, 24 October 2008; 1 ♀, NMNS 8772-64, 5.8 × 3.8, Wanlitong, Pingtung County, 13 May 2009; 1 ♀, NMNS 8772-65, 6.3 × 4.2, Jihuei, Taitung County, 13 December, 2012. Fig. 20. Xanthias lamarckii (H. Milne-Edwards, 1834) (female, CW 6.3 mm; NMNS 8772-65), A; Atergatis floridus (Linnaeus, 1767) (female, CW 5.8 mm; NMNS 8772-66), B; Zozymodes pumilus (Hombron and Jacquinot, 1846 [in Hombron and Jacquinot, 1842–1854]), female (CW 9.1 mm; NMNS 8772-70); male (CW 5.6 mm; NMNS 8772-67), C, D: A–C, habitus, dorsal view; D, G1, right, distal area, external view. Scale bars: A = 2.0 mm; B = 1.0 mm; C = 3.0 mm; D = 0.1 mm. page 32 of 38 Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan Distribution: Indo-Pacific (Serène 1984). Remarks: Xanthias lamarckii (H. Milne Edwards, 1834) (Fig. 20A) has been frequently documented in Taiwanese waters (Ng et al. 2017). This study reports a new collection location for this species along the eastern coast of Taiwan. Subfamily Zosiminae Alcock, 1898 Genus Atergatis De Haan, 1833 Atergatis floridus (Linnaeus, 1767) (Fig. 20B) Cancer floridus Linnaeus 1767: 1041. Atergatis floridus Dai et al. 1986: 261, text-fig. 150A(1), pl. 35(8); Dai and Young 1991: 282, text-fig. 150A(1), pl. 26(8); Ng and Davie 2007: 169–172, figs. 2A–C, 3A, 4A, C (for the discussion of synonymy); Ng et al. 2008: 205, 209; Ng et al. 2017: 94 (for complete collection records from Taiwan). Material examined: 1 ♀, NMNS 8772-66, 5.8 × 4.0, Jihuei, Taitung County, 13 December 2012. Distribution: Widely distributed in the Indo-West Pacific (Dai and Young 1991). Remarks: The morphology of the present specimen (Fig. 20B) aligns with the neotype of this species as designated by Ng and Davie (2007). Reports of this species in Taiwan have been documented over the past century (Ng et al. 2017). Genus Zozymodes Heller, 1860 Zozymodes pumilus (Hombron and Jacquinot, 1846) (Fig. 20C, D) Zozymodes pumilus Serène 1984: 153, fig. 90, pl. XIX E (for complete synonymy); Hsueh et al. 2009: 1026; Ng et al. 2008: 206 [List]; Ng et al. 2017: 95. Material examined: 1 ♂ 1 ♀NMNS 8772-67, 5.5–5.6 × 3.7–3.8, Shanfu, Liuqiu Township, Pingtung County, 4 May 2007; 1 ♂ 3 ♀NMNS 8772-68, 6.5–9.2 × 4.1–5.6, Jihuei, Taitung County, 7–9 October, 2010; 1 ♂ 7 ♀ (including 2 ovigerous individuals) NMNS 8772-69–72, 5.4–10.0 × 3.1–5.3, Jihuei, Taitung County, 28–29 April, 2017. Distribution: Indo-Pacific (Serène 1984). Remarks: The morphology of the present specimens (Fig. 20C, D) matches the key characteristics of Zozymodes pumilus (Hombron and Jacquinot, 1846) (Serène 1984: 152, fig. 90, pl. XIX E; Lasley and Ng 2013: 8–9, fig. 4B). Hsueh et al. (2009) first recorded this species based on specimens collected from Wanlitong, Pingtung County, southern Taiwan. Li et al. (2010) reported it from Liuqiu Island, off southwestern Taiwan. This study documents a new collection location for the species along the coasts of eastern Taiwan. DISCUSSION The size of xanthid crabs varies greatly among species. The adult carapace width of some species (i.e., Lioxanthodes alcocki Calman, 1909) can be as small as a few millimeters, whereas in others (i.e., Atergatis latissimus (H. Milne-Edwards, 1834), it can exceed 100 millimeters (Serène 1984). Specimens from the present study were excavated from small rock crevices in intertidal habitats, and their sizes tended to be small, with carapace widths not exceeding 15 millimeters. This suggests that most of them are likely in their juvenile or adolescent of life stage. Evidence supporting this observation includes the triangular or oval shapes of the female pleon in most specimens (Figs. 5D, 7G, 9H, 13H, 14H, 18D). Exceptions include two egg-bearing females (Liocarpilodes harmsi, CW 6.7 and 4.8 mm; NMNS 8772-29, 36), one egg-bearing female (Lioxanthodes alcocki, CW 6.2 mm; NMNS 8772-56), and two egg-bearing females (Zozymodes pumilus, CW 9.4 and 10.4 mm; NMNS 8772-71, 72). Proper identification of juvenile xanthid crabs can be challenging due to potential ontogenetic morphological changes. CONCLUSION The present study reviews xanthid crabs collected from rocky intertidal habitats in Taiwan and nearby offshore islands during ecological surveys conducted over the past 25+ years. A total of 24 species are recognized, represented by seven subfamilies and 16 genera in the family Xanthidae MacLeay, 1838. The subfamilies are Actaeinae Alcock, 1898, Chlorodiellinae Ng and Holthuis, 2007, Etisinae Ortmann, 1893, Euxanthinae Alcock, 1898, Liomerinae T. Sakai, 1976, Xanthinae MacLeay, 1838, and Zosiminae Alcock, 1898. The 16 genera include Actaeodes Dana, 1851, Atergatis De Haan, 1833, Chlorodiella Rathbun, 1897, Cyclodius Dana, 1851, Etisus H. Milne Edwards, 1834, Leptodius A. Milne-Edwards, 1863, Liocarpilodes Klunzinger, 1913, Liomera Dana, 1851, Lioxanthodes Calman, 1909, Luniella Lasley, Klaus and Ng, 2015, Macromedaeus Ward, 1942, Paraxanthias Odhner, 1925, Pilodius Dana, 1851, Psaumis Kossmann, 1877, Xanthias Rathbun, 1897, and Zozymodes Heller, 1860. Lioxanthodes is recorded from Taiwan for the first time. Of the 24 recognized species, 14 have been previously page 33 of 38Zoological Studies 63:47 (2024) © 2024 Academia Sinica, Taiwan reported from Taiwan, five are new record to Taiwan, one is new to science, and four unnamed species. The new records include Chlorodiella barbata (Borradaile, 1900), Etisus frontalis (Dana, 1952), Lioxanthodes alcocki Calman, 1909, Macromedaeus quinquedentatus (Krauss, 1843), and Pilodius nigrocrinitus Stimpson, 1859. The new species, Cyclodius taiwanensis sp. nov., is described herein. Acknowledgments: This study was partially supported by the Ministry of Science and Technology, Republic of China (MOST 108-2621-B-005-004MY3) awarded to PWH. We extend our gratitude to Mr. J-H Chang, H-T Hong, K-R Li, Y-H Li, and J-H Zhu for their assistance with field collections. We also appreciate the valuable comments on this manuscript provided by Drs J.C.E. Mendoza and P.K.L. Ng. Authors’ contributions: The first author is responsible for specimen collection and examination, drafting the manuscript, and creating most of figures and tables. The co-author contributed to field collections and produced all the line drawings included in this manuscript. Both authors reviewed and approved the final draft prior to its submission to Zoological Studies. Competing interests: PWH and YWT declare that they have no conflict of interest. Availability of data and materials: Not applicable. Consent for publication: Not applicable. Ethics approval consent to participate: Not applicable. REFERENCES Alcock A. 1898. Material for a carcinological fauna of India. No. 3. The Brachyura Cyclometopa. Part I. The Family Xanthidae. J Asia Soc Bengal 67:67–233. Alcock A, Anderson ARS. 1894. Natural History Notes from H.M. Indian Marine Survey Steamer « Investigator ». Ser. II. N° 17. List of the Shore and Shallow-water Brachyura collected during the Season 1893–1894. J Asiat Soc Beng 63:197–209 [l–13]. Balss H. 1922. Ostasiatische Decapoden. IV. Die Brachyrhynchen (Cancridea). Arc Naturgesch 88:94–166, figs. 1–2, pls. 1–2. Balss H. 1924. Decapoden des Roten Meeres. III. Die Parthenopiden, Cyclound Catometopen. 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