Zoosyst. Evol. 100 (3) 2024, 965-987 | DOI 10.3897/zse.100.117859 Ge Ee BERLIN Morphological and molecular evidence for Gothus teemo gen. et sp. nov., a new xanthid crab (Crustacea, Brachyura, Xanthoidea) from coral reefs in the South China Sea, with a review of the taxonomy of Actaeodes consobrinus (A. Milne-Edwards, 1867) Zi-Ming Yuan! *>4, Wei Jiang!:*°, Zhong-Li Sha!* Department of Marine Organism Taxonomy and Phylogeny, Institute of Oceanology, Chinese Academy of Sciences, Oingdao 266071, China Laoshan Laboratory, Qingdao 266237, China Shandong Province Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China C3 ho. College of Biological Sciences, University of Chinese Academy of Sciences, Beijing 100049, China https://zoobank. org/15CA9YED4-C24C-4A D7-81AC-F699FAIS3 FES Corresponding author: Zhong-Li Sha (shazl|@qdio.ac.cn) Academic editor: M. Christodoulou # Received 27 December 2023 Accepted 13 June 2024 Published 9 July 2024 Abstract A new genus and species within the family Xanthidae MacLeay, 1838, are described from coral reefs in the South China Sea. The new genus, Gothus, with its type species G. feemo sp. nov., is distinguishable from allied genera by characteristics of the carapace, chelipeds, and male pleon. Based on morphological evidence, we tentatively place this genus within the subfamily Euxanthinae Alcock, 1898. However, molecular systematic analysis based on COI, 12S, 16S, and H3 indicates that it does not form a sta- ble monophyletic group with any related subfamily. Another species, Actaeodes consobrinus (A. Milne-Edwards, 1873), is also reclassified into this new genus, based on both morphological and molecular evidence. Key Words Euxanthinae, integrative taxonomy, Nansha Islands, Xanthidae, Xisha Islands Introduction Xanthidae MacLeay, 1838, is one of the most diverse families in Brachyura, comprising 639 species across 124 genera (updated from Ng et al. 2008). Recent molecu- lar phylogenetic studies have gradually deciphered the complex internal systematic and evolutionary relation- ships within this large taxonomic group (Lai et al. 2011; Thoma et al. 2014; Mendoza et al. 2022). However, the morphological delineation of various clades still requires further investigation. Potentially undiscovered taxa may also offer novel insights into or challenge the classifica- tion system of this group. During a recent biological research expedition to the coral reefs of the South China Sea, we discovered a small and distinctive species of Xanthidae in the Xisha Islands (Paracel Islands) and Nansha Islands (Spartly Islands), which we confirmed as a new genus and spe- cies. We discussed its taxonomic status within the family using an integrative taxonomic approach that combines morphological and molecular phylogenetics, with par- ticular focus on its subfamily affiliation. Additionally, we revisited the taxonomic status of another common species of the South China Sea coral reefs, Actaeodes consobrinus (A. Milne-Edwards, 1873), reassigning it to the present new genus. Copyright Yuan, Z.-M. et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 966 Yuan, Z.-M. et al.: Anew genus and species of Xanthidae crab from the South China sea Materials and methods Specimens were obtained during scuba diving at coral reefs in the South China Sea, subsequently photographed, and conserved in 70% ethyl alcohol. These specimens have been deposited at the Marine Biological Museum, Chinese Academy of Sciences in Qingdao, China (MBM). Mor- phology was observed using a ZEISS SteREO Discovery stereoscopic microscope. Photographs were captured using a Canon EOS 6D camera with a Canon MP-E 65 mm lens, a Nikon D800 camera with a Nikon AF-S 105 mm lens, or a ZEISS Axiocam 506 microscope camera. The terminology used in this paper mainly follows that of Serene (1984) and Davie et al. (2015). The follow- ing abbreviations were used: CW = maximum carapace width; CL = median carapace length; G1 = first gonopod of male; G2 = second gonopod of male. The molecular sequences used in this study were pri- marily obtained from NCBI, particularly from Lai et al. (2011) and Mendoza et al. (2022) (Table 1). The sequences acquired in this study were obtained through the follow- ing methods: DNA was extracted from muscle tissue using the OMEGA EZNA Tissue DNA Kit (USA). Molecular characters were derived from three mitochondrial and one nuclear markers: mitochondrial 12S rRNA (12S, approxi- mately 363 bp), 16S rRNA (16S, approximately 521 bp), cytochrome oxidase I (COI, approximately 658 bp), and nuclear histone H3 (H3, approximately 328 bp). 44 species within the family Xanthidae and two outgroup taxa were encompassed in the phylogenetic analysis (Suppl. materi- al 1). Amplification was carried out via polymerase chain reaction (PCR), employing primers 12sf and 12s1r for 12S (Buhay et al. 2007), 16Sar and 16Sbr for 16S (Palumbi, 1996), Hex-AF and Hex-AR for H3 (Svenson & Whiting, 2004), and either jgl.CO1490 and jgHCO2198 (Geller et al. 2013) or Pano-F and Pano-R (Thoma et al. 2014) for COI. The amplification protocol was as follows: initial denatur- ation at 94 °C for 3 min, followed by 35 cycles of denatur- ation at 94 °C for 30 s, annealing at 60 °C for 12 s, 48 °C for 16 s, 48 °C for COI, 66 °C for H3 for 45 s each, extension at 72 °C for 45 s, and a final extension at 72 °C for 10 min. The sequences obtained were aligned using MEGA 6 (Tamura et al. 2013) and concatenated using Sequence- Matrix 1.8 (Vaidya et al. 2011), resulting in a combined sequence length of 2019 bp. Phylogenetic trees were con- structed using the maximum likelihood (ML) method and Bayesian inference (BI). The optimal model of evolution for each dataset was determined using jModelTest 0.1.1 based on the Akaike information criterion (AIC) (Posada, 2008). Bayesian analyses were executed with MrBayes 3.2.7 (Huelsenbeck & Ronquist, 2001), employing a Mar- kov Chain Monte Carlo (MCMC) algorithm with two runs, each consisting of four chains, for 1,000,000 generations and sampling trees every 500 generations, totaling 2,000 sampled trees. The initial 500 trees were discarded as burn-in, and posterior probabilities were calculated from the remaining trees. The ML analyses were conducted on- line using W-IQ-TREE (http://iqtree.cibiv.univie.ac.at/) zse.pensoft.net (Jana et al. 2016), with clade support evaluated via 10,000 ML bootstrap replications. Multiple species delimitation methods were utilized to assess the hypothesis that the specimen is a distinct species. The COI data, comprising 17 homologous sequences, were subjected to automated barcode gap discovery (ABGD) analysis using a web-based interface (https://bioinfo.mnhn. fr/abi/public/abgd/abgdweb.html), as described by Puil- landre et al. (2012). The analysis was conducted using the Kimura 2-parameter substitution model (TS/TV = 2.0), with a prior range for maximum intraspecific divergence set be- tween 0.001 and 0.1, encompassing 10 recursive steps, and a relative gap width (X) of 1.0. Additionally, Bayesian im- plementation of the Poisson tree processes (PTP) species de- limitation model was employed as per Zhang et al. (2013), conducted on the web server of the Heidelberg Institute for Theoretical Studies, Germany (http://species.h-its.org/), using BI phylogenetic trees as the input data. Results Systematic account Family Xanthidae MacLeay, 1838 Subfamily Euxanthinae Alcock, 1898 Gothus gen. nov. https://zoobank.org/240FAE30-235A-49A 8-995D-6209A 7F6899 | Figs 1-5 Type species. Gothus teemo sp. nov., by present desig- nation. Diagnosis. Small species, CW under 10 mm. Carapace broader than long, dorsal surface bearing round granules, regions clearly defined; front wide, not protruding, divid- ed into two slightly triangular lobes by a V-shaped notch; frontal lobes and dorsal inner orbital angle separated by shallow depression; eyestalks densely granulated; area beneath outer orbital angle slightly concave, not forming a subhepatic cavity; anterolateral margin with four teeth, first tooth flattened, sometimes completely reduced to ap- pear as three teeth; posterolateral margin almost straight; subhepatic region densely granulated. Epistome central region with low median projection on posterior margin. Maxilliped 3 granulated, anterior edge of merus indented, external terminal angle expand- ed. Antennule folding transversely; basal segment of an- tenna subrectangular; contacting ventral external frontal margin and ventral internal orbital angle; antennal flagel- lum filling orbital hiatus. Chelipeds symmetrical, merus short; carpi robust, surface granulated, aggregated into nodules; outer and dorsal surfac- es of palm densely granulated; fingers elongated, with trian- gular teeth; tips sharp, crossing at extremities when closed; dorsal surface of movable finger with three granulated ridg- es. Fingers brownish-black, coloration of immovable finger extending onto inner and outer surfaces of palm in male. Zoosyst. Evol. 100 (3) 2024, 965-987 967 Table 1. Details of specimens and GenBank accession numbers used in this study. Species Locality Voucher Col 16S 12S H3 Sources Actaea pura Stimpson, 1858 Xiamen, Fujian, China APO1 PPO28728 PP024661 PP025373 PPO01490 present study Actaeodes hirsutissimus (Ruppell, 1830) Milne Bay Province, USNM:1467002 MZ560478 NA NA NA Plaisance et al. Papua New Guinea 2021 Actaeodes hirsutissimus (Ruppell, 1830) Pulau Bintan, Indonesia ZRC 2008.1143 NA HM798418 HM851287 HM798267 Laietal. 2011 Actaeodes tomentosus (H. Milne-Edwards, Pulau Sapi, Sabah, ZRC 2000.1673 HM750947 HM798420 HM851289 HM798269 Laietal. 2011 1834) Malaysia Atergatis integerrimus (Lamarck, 1818) Beting Bronok Reef, ZRC 2007.0252 HM750950 HM798423 HM851292 HM798271 Laietal. 2011 Singapore Banareia nobili (Odhner, 1925) Bolod, Panglao Island, = ZRC 2010.0131 HM750954 HM798429 HM851299 HM798277 Laietal. 2011 Philippines Chlorodiella nigra (Forskal, 1775) Bar Al Hikman Peninsula, UF 17948 HM750961 HM798437 HM851307 HM798286 Laiet al. 2011 Oman Cymo quadrilobatus Miers, 1884 NA ZRC 2009.1173 HM750969 HM798443 HM851314 HM798292 Laietal. 2011 Demania intermedia Guinot, 1969 Northwest coast of ZRC 2009.0187 HM750972 HM798448 HM851319 HM798297 Laietal. 2011 Panglao, Philippines Eriphia gonagra (Fabricius, 1781) NA ULLZ 5463 HM638035 HM637964 HM637933 HM596633 Direct Submission Ftisus anaglyptus H. Milne-Edwards, 1834 Paya Beach, Paya Beach, ZRC 1999.0931 HM750975 HM798451 HM851322 HM798300 Laietal. 2011 Malaysia Euxanthus exsculptus (Herbst, 1790) Paya Beach, Pulau ZRC 2002.0535 HM750983 HM798460 HM851332 HM798310 Laietal. 2011 Tioman, Malaysia Euxanthus herdmani Laurie, 1906 Looc, Panglao Island, NMCR 27334 ~HM750984 HM798461 HM851333 HM798311 Laietal. 2011 Philippines Euxanthus huonii (Hombron & Jacquinot, Pontod Isle, Panglao ZRC 2008.1376 HM750985 HM798462 HM851334 HM798312 Laietal. 2011 1846) Island, Philippines Euxanthus ruali Guinot, 1971 E Aoré Island, Aimbué ZRC 2009.1178 HM750986 HM798463 HM851335 HM798313 Laietal. 2011 Bay, Vanuatu Forestiana depressa (White, 1848) NA ZRC1998.404 NA MZ412992 NA MZ823053 Mendoza et al. 2022 Gaillardiellus rueppelli (Krauss, 1843) Weizhou Island, Guangxi, G02 PPO28729 PP024662 PPO025374 PPOO1491 present study China Gothus consobrinus comb. nov. Yongshu Reef, Nansha NS-YS-2022-1336 PP028733 PP024664 PP025376 PPO001493 present study Islands, China Gothus consobrinus comb. nov. Meiji Reef, Nansha NS-MJ-2022-1438 PP028736 NA NA NA present study Islands, China Gothus consobrinus comb. nov. Qilianyu, Xisha Islands, | XS-QL-2022-1014 PP028737 NA NA NA present study China Gothus teemo sp. nov. Meiji Reef, Nansha NS-MJ-2022-1287 PP028734 NA NA NA present study Islands, China Gothus teemo sp. nov. Meiji Reef, Nansha 2304278486 NA PPO24665 PPO025377 PPO01494 present study Islands, China Hepatoporus orientalis (Sakai, 1935) Off western coast ZRC 2008.1379 HM750994 HM798471 HM851343 HM798321 Laietal. 2011 ofBatangas, Philippines Hypocolpus abbotti (Rathbun, 1894) NA UF 14978 HM750995 HM798472 HM851344 HM798322 Laietal. 2011 Hypocolpus diverticulatus (Strahl, 1861) Northwest of Nosy UF 14076 HM750997 HM798474 HM851346 HM798324 Laietal. 2011 Komba, Madagascar Hypocolpus pararugosus Crosnier, 1996 Balicasag Island, ZRC 2008.1389 HM750998 HM798475 HM851347 HM798325 Laietal. 2011 Philippines Liagore rubromaculata (De Haan, 1835) Cortes, Bohol Island, ZRC 2010.0143 HM751006 HM798484 HM851356 HM798334 Laietal. 2011 Philippines Liomera cinctimanus (White, 1847) Apra harbour, Guam ZRC 2000.0730 HM751008 HM798486 HM851358 HM798336 Laietal. 2011 Lybia tessellata (Latreille in Milbert, 1812) Southwest of Orote ZRC 2000.0710 HM751017 HM798497 HM851369 HM798346 Laietal. 2011 Peninsula, Guam Macromedaeus crassimanus H. Milne Balicasag Island, ZRC 2003.0369 HM751018 HM798498 HM851370 HM798347 Laietal. 2011 Edwards, 1834 Philippines Menippe rumphii (Fabricius, 1798) Labrador Beach, ZRC 2003.0211 HM638051 HM637976 HM637946 HM596626 = Laiet al. 2011 Singapore Neoliomera striata Buitendijk, 1941 Yuzhuo Reef, Xisha TX02 PP028735 PP024666 NA PPOO1495 __ present study Islands, China Neoxanthias michelae Seréne & Vadon, Pichai fishing port, ZRC 1999.0516 HM751038 HM798522 HM851394 HM798371 Laietal. 2011 1981 Phuket, Thailand Novactaea bella Guinot, 1976 Pulau Bintan, Indonesia ZRC 1998.0981 HM751044 HM798529 HM851401 HM798378 Laietal. 2011 Olenothus uogi Ng, 2002 Guam ZRC 2002.0176 HM751046 HM798531 HM851403 HM798380 Laiet al. 2011 Paractaea rufopunctat(H. Milne Edwards, Pago Bay, Guam ZRC 2000.0718 HM751048 HM798535 HM851407 HM798383 Laiet al. 2011 1834) Paractaeopsis quadriareolata (Takeda & NA UF 16755 MZ400990 MZ413003 NA MZ823064 Mendoza et al. Miyake, 1968) 2022 Paratergatis longimanus Sakai, 1964 Taichi Port, Han county, ZRC 1998.0047 HM751051 HM798538 HM851410 NA Lai et al. 2011 Taiwan Island, China zse.pensoft.net 968 Yuan, Z.-M. et al.: Anew genus and species of Xanthidae crab from the South China sea Species Locality Voucher Col 16S 12S H3 Sources Platypodia pseudogranulosa Seréne, 1984 — Cyrene Reef, Singapore ZRC 2008.0492 HM7/51058 HM798546 HM851418 HM798393 Laietal. 2011 Psaumis cavipes (Dana, 1852) Yongle blue hole, Xisha AOPO3 PP028730 NA NA NA present study Islands, China Psaumis cavipes (Dana, 1852) Panglao Island, Sungcolan ZRC 2010.0157 NA HM798549 HM851421 HM798395 = Laietal. 2011 Bay, Philippines Pseudoliomera granosimana (A. Milne- NA UF 10496 MZ400994 MZ413006 NA MZ823067 Mendoza et al. Edwards, 1865) 2022 Pseudoliomera speciosa (Dana, 1852) Zhongsha Islands, China ZS57 PP028732 PP024663 PP025375 PPO01492 present study Pulcratis reticulatusNg & Huang, 1997 Ping-tung County, Taiwan ZRC 1997.0402 HM751064 HM798553 HM851425 HM798399 Laietal. 2011 Island, China Rizalthus anconis Mendoza & PKL Ng, 2008 Meiji Reef, Nansha NS-MJ-2022-1457 PP0O28731 NA NA NA present study Islands, China Rizalthus anconis Mendoza & PKL Ng, 2008 = Pontod lagoon, Panglao ZRC 2008.0215 NA HM798555 HM851427 HM798401 _Laietal. 2011 Island, Philippines Visayax osteodictyon Mendoza & Ng, 2008 Panglao Island, ZRC 2008.0753 HM751070 HM798559 HM851432 HM798405 = Laietal. 2011 Philippines Xanthias canaliculatus Rathbun, 1906 Sodwana Bay, South ULLZ 4381 MZ400999 EU863382 EU863316 GU144502 Mendoza et al. Africa 2022; Thoma et al. 2009; Felder and Thoma 2010 Xanthias joanneaeMendoza, 2013 NA ZRC 2013.0435 MZ400998 MZ413008 NA MZ955031 Mendoza et al. 2022 Xanthias latifrons (De Man, 1887) Tepungan Channel, Guam ZRC 2000.0728 HM751072 HM798561 HM851434 HM798407 Laietal. 2011 Zalasius sakaii Balss, 1938 Mitou, Kaoshiung county, ZRC 1997.0399 HM751077 HM798566 HM851439 HM798413 Lai etal. 2011 Taiwan,China Zosimus aeneus (Linnaeus, 1758) Heng Chun Peninsula, ZRC 1998.0388 HM751078 HM798567 HM851440 HM798414 Laietal. 2011 Taiwan Island, China Ambulatory legs with meri flattened, granulated along anterior and posterior edges; dactyli elongated, margins with granules and setae, terminal end chitinous, sharp, slightly curved backward, dactylo-propodal lock present but underdeveloped. Male thoracic sternum with sternites 1 and 2 com- pletely fused, suture between sternites 2 and 3 straight, complete, sternites 3 and 4 mostly fused, suture between them visible only at margins, sternites 3 short, sternite 4 with central longitudinal groove, tubercle of sterno-ple- onal lock located on posterior of sternite 5. Male pleon narrow, pleonites 3 to 5 completely fused, lateral margins of pleonite 6 slightly concave. Telson long, broad, trun- cated oval, base margin wider than terminal margin of pleonite 6. G1 slender, curving slightly outward, distal lobe spoon-shaped, long setae on inner subdistal part, small spines on outer part. G2 not exceeding 1/6 length of G1, distal lobe elongated. Etymology. The genus is named after the game of Go, alluding to the intermingled black and white patterns on the carapace, beneath which lie circular granules resembling the pieces of the game. “-thus” is a common suffix for species names within the Xanthidae family. Gender masculine. Comparative material. Rizalthus anconis Men- doza & PKL Ng, 2008 (Fig. 6A). CHtNA « 1 female; CW 4.2 mm, CL 2.7 mm; Meiji Reef, Nansha Islands; 9°52'38.19"N, 115°31'17.08"E; 8 m; 7 May 2022; Ziming Yuan, Yuli Sun, Shaobo Ma coll.; NS-MJ-2022-1457. Aypocolpus haanii Rathbun, 1909 (Fig. 6B). Cui- NA * 1 male; CW 45.3 mm, CL 34.2 mm; Lingao Cape, Hainan Island; 15—30 m; 20 Aug. 2018; Yunhao Pan coll.; MBM286755. zse.pensoft.net Euxanthus exsculptus (Herbst, 1790) (Fig. 6C). CHINA * 1 male; Wenchang, Hainan Island; 20 Dec. 2018; Yunhao Pan coll.; Xan016 « 1 male; Yongxing Is- land, Xisha Islands; 15—17 May 1957; MBM163793 « 2 males; Wood Island, Xisha Islands; 1957; MBM163791 ¢ 1 male, 2 females; Wood Island, Xisha Islands; 15-17 May 1957; MBM163788 ¢ 3 males, 3 females; East Is- land, Xisha Islands; 28-31 May 1980; MBM163785 « 1 female; Yongxing Island, Xisha Islands; 11—13 Jun. 1980; MBM163784 ¢ 1 female; East Island, Xisha Islands; 12 Jun. 1975; Xianqiu Ren coll.; MBM163792. CW 15-52.8 mm, CL 9.7—33.2 mm. Euxanthus huonii (Hombron & Jacquinot, 1846) (Fig. 6D). CuiNa * 1 male; Dengqing Island, Xisha Is- lands; 11-17 Apr. 1958; MBM163762 « 1 female; Tree Island, Xisha Islands; 1 May 1958; MBM163761 « 1 female; Yongxing Island, Xisha Islands; 7 May 1980; MBM163780 « 2 females; Drummond Island, Xisha Is- lands; 1980; MBM163781 ¢ 1 male; Meiji Reef, Nansha Islands; 9°53'30.84"N, 115°34'22.05"E; 10 m; 10 May 2022; Ziming Yuan, Yuli Sun, Shaobo Ma coll.; NS- MJ-2022-1734. CW 19.3-37.3 mm, CL 13.1—26.4 mm. Psaumis cavipes (Dana, 1852) (Fig. 6E). CHINA ¢ | female ovigerous; Xisha Islands, Jinging Island; 10 Jul. 2019; azp0O1 * 1 male, 3 females; Sanya Station Front, Hainan; 30 Apr. 2021; Zhang Xu coll.; aop01 * 2 males; Xisha Islands, Yongle blue hole; 10 Jul. 2019; aop02 ¢ | female ovigerous; Xisha Islands, Yongle blue hole; 10 Jul. 2019; aop03 ¢ 1 male; Phoenix Island, Sanya, Hainan; Zhang Xu coll.; 2022010 * 1 juvenile; Xisha Islands, Yu- zhuo Reef; 9 Jul. 2019; aop04 * 2 males; Hainan, subtidal 9-10 m; 21 Nov. 2016; Xan020-2. CW 5.1—17.4 mm, CL 3.3-10.6 mm Zoosyst. Evol. 100 (3) 2024, 965-987 969 Figure 1. Gothus teemo sp. nov. A-C. Holotype, male, CW 3.7 mm, CL 2.6 mm, MBM287027; D-F. Paratype, CW 3.2 mm, CL 2.2 mm, MBM287026; A, D. Dorsal view; B, E. Frontal view; C, F. Carapace. Scale bar: 1 mm. Remarks. Gothus gen. nov. exhibits the closest re- semblance to the subfamily Euxanthinae, particularly to Eux 1, as defined and morphologically summarized in the molecular systematic study by Lai et al. (2011)., mainly considering its anterolateral margin of the cara- pace, which does not clearly meet the orbit but instead continues down to the subhepatic region, presenting an ambiguous starting point (Fig. 1B). Other characteristics justifying its inclusion are chelipeds almost completely symmetrical, which can be coapted against the carapace (Fig. 1A); male pleon long, with the telson reaching to the level above the coxo-sternal condyles of pereiopod 1, and base of somite 3 only slightly wider than tip of somite 5 (Figs 2F, 3F) (see also Serene, 1984; Lai et al. 2011). However, its ambulatory legs do not form a similar per- fect coapted structure, especially since the corresponding posterolateral margin is nearly non-concave (Fig. 1A, C). Other features notably distinguishing it from any member of the subfamily Euxanthinae are its extremely narrow male pleon with a long and broad, overall truncated oval telson (Figs 2F, 3F), the base of which is wider than the width of the end of the sixth pleonite, the terminal end wide and rounded, with the lateral edges barely converg- ing inward but rather forming two opposing arcs, unlike the typically triangular telson common in the Euxanthinae. Gothus gen. nov. shares the closest similarities with the genus Rizalthus Mendoza & PKL Ng, 2008, due to both possessing a granule-covered carapace surface, zse.pensoft.net 970 Yuan, Z.-M. et al.: Anew genus and species of Xanthidae crab from the South China sea Figure 2. Gothus teemo sp. nov. A, C, E. Holotype, male, CW 3.7 mm, CL 2.6 mm, MBM287027; B, D, F, G. Paratype, female, CW 3.2 mm, CL 2.2 mm, MBM287026; A. Male chelipeds; B. Female chelipeds; C. Male thoracic sternites; D. Female thoracic sternites; E. Male pleon; F. Female pleon; G. Female vulva. Scale bar: 1 mm (A—F); 0.2 mm (G). similar carapace outlines and front, developed cheliped carpus, and analogous G1 structures. However, Gothus can be easily distinguished from Rizalthus by several key characteristics: its anterolateral margin with four teeth, first tooth flattened, sometimes completely reduced to zse.pensoft.net appear as three teeth (Figs 1A, C, 3A) (vs. no clearly de- fined teeth in Rizalthus, Fig. 6A; cf. Mendoza and Ng 2008: fig. 1A); absence of etched depressions on body (Fig. 1A) (vs. distinct etched depressions on thoracic ster- num in Rizalthus; cf. Mendoza and Ng 2008: fig. 1C); Zoosyst. Evol. 100 (3) 2024, 965-987 re gine Pant c ae exe Corb oS oO Cee ee wee e Kreg Oe 971 Figure 3. Gothus teemo sp. nov. A-C, F, G—L. Holotype, male, CW 3.7 mm, CL 2.6 mm, MBM287027; D, E. Paratype, female, CW 3.2 mm, CL 2.2 mm, MBM287026; A. Carapace; B. Maxilliped 3; C. Cheliped; D. Pereopod 5; E. Female pleon; F. Male pleon; G. right G1, ventral view; H. Same, dorsal view; I. Right G1, distal part, ventral view; J. Same, dorsal view; K. Right G2, ventral view; L. Same, dorsal view. Scale bar: 1 mm (A, C, D); 0.5 mm (B, E, F, G, H); 0.1 mm (I-L). central part of epistome raised (Fig. 1B) (vs. central part of epistome not protruding in Rizalthus; cf. Mendoza and Ng 2008: fig. 1B); robust cheliped carpus, sometimes slightly expanded (Fig. 1A) (vs. strongly expanded and protruding in Rizalthus, Fig. 5A; cf. Mendoza and Ng 2008: fig. 1A); male pleon with a long, broad, truncated oval telson (Figs 2F, 3F) (vs. a smaller, triangular telson in Rizalthus; cf. Mendoza and Ng 2008: fig. 2C); G1 dis- tal lobe curved inwards (Fig. 3G—J) (vs. nearly straight, not curved inwards in Rizalthus, cf. Mendoza and Ng zse.pensoft.net 972 Yuan, Z.-M. et al.: Anew genus and species of Xanthidae crab from the South China sea x _ Pana a Aa 2008: fig. 2F—H) and G2 with a longer, straighter distal lobe (Fig. 3K, L) (vs. shorter and curved in Rizalthus;, cf. Mendoza and Ng 2008: fig. 21). Due to its similar carapace outline, particularly the less concave posterolateral margins, Gothus also resem- bles Visayax Mendoza & Ng, 2008. However, it can be zse.pensoft.net Pes. Figure 4. Gothus teemo sp. nov. A, B. Holotype, male, CW 3.7 mm, CL 2.6 mm, MBM287027; C-E. Paratypes, 2 juvenile, CW 1.8—2.2 mm, CL 1.3—1.5 mm, MBM287023; A-D. Live coloration; E. Habitat and substrate conditions. Scale bar: 1 mm. a ame * d - t - « wy easily differentiated by the following characteristics: Go- thus lacks erosive depressions across body (Fig. 1A) (vs. chelipeds, ambulatory legs, carapace, and thoracic ster- num with erosive depressions in Visayax; cf. Mendoza and Ng 2008: figs 3-6); carapace regions more flattened (Fig. 1A, C) (vs. carapace regions more pronounced in Zoosyst. Evol. 100 (3) 2024, 965-987 ge! ie : 9 ag X J) Wy) t lira t > Figure 5. Gothus teemo sp. nov., paratype, female, CW 3.2 mm, CL 2.2 mm, MBM287026, artistic illustration, displaying live coloration. Drawn by Fei Gao. Visayax, cf. Mendoza and Ng 2008: figs 3A, C, 5A, C); posterior three teeth on anterolateral margin of carapace well-developed (Fig. 1A, C, 3A) (vs. absence of devel- oped teeth on anterolateral margin in Visayax; cf. Men- doza and Ng 2008: figs 3A, 5A); male abdominal telson larger, truncated oval (Figs 2F, 3F) (vs. smaller, semi-cir- cular in Visayax; cf. Mendoza and Ng 2008: figs 4E, 6D); G1 more slender (Fig. 3G—J) (vs. G1 more robust in Vi- sayax; cf. Mendoza and Ng 2008: figs 4F, G, 6F, G). The new genus exhibits a general morphological simi- larity to typical Euxanthinae members such as Euxanthus Dana, 1851, and Hypocolpus Rathbun, 1897. In addition to the existing comparative specimens, Guinot-Dumortier (1960) provided excellent descriptions and photographs of species from the above two genera. Subsequently pub- lished species also have relatively clear morphological descriptions and images available for comparison (cf. Guinot 1971b; Galil and Vannini 1990; Crosnier 1996). The new genus can be easily distinguished from Euxan- thus by the following features: entire body covered with granules and short pubescence (Fig. 1A) (vs. relatively smooth in Euxanthus, Fig. 6C, D; cf. Guinot-Dumortier 1960: pl. VIII, figs 42, 44, 46, pl. IX, figs 48-52); cara- pace anterolateral margin with four teeth, first tooth flat- tened, sometimes completely reduced to appear as three teeth (Figs 1A, C, 3A) (vs. 4-6 teeth on anterolateral margin in Euxanthus; Fig. 6C, D; cf. Guinot-Dumortier 1960: pl. VIII, figs 42, 44, 46, pl. IX, figs 48-52); front not prominent, divided by a V-shaped notch (Figs 1C, 3A) (vs. more protruding, divided by a narrow fissure in Euxanthus, Fig. 6C, D; cf. Guinot-Dumortier 1960: pl. VIII, figs 42, 44, 46, pl. EX, figs 48-52); male abdominal telson large and truncated oval (Figs 2F, 3F) (vs. small and triangular in Euxanthus; cf. Guinot-Dumortier 1960: pl. VIII, fig. 47); G1 with a prominent, spoon-shaped dis- tal lobe, and long setae on inner subdistal part (Fig. 3G—J) (vs. G1 with a short, non-protruding distal lobe, inward- ly curved and encircling, with short setae on inner sub- distal part in Euxanthus, cf. Guinot-Dumortier 1960: pl. VI, figs 36-39). Similarly, the new genus is easily distin- guishable from Hypocolpus by the absence of a devel- oped subhepatic cavity (Fig. 1B) (vs. a developed subhe- patic cavity in Hypocolpus; cf. Guinot-Dumortier 1960: pl. I, figs 40-41); posterior three teeth on anterolateral margin well-developed (Figs 1C, 3A) (vs. underdevel- oped teeth in Hypocolpus, Fig. 6B; cf. Guinot-Dumortier 1960: pl. VII, figs 40-41); front not prominent, divided by a V-shaped notch (Figs 1C, 3A) (vs. more protruding, divided by a narrow fissure in Hypocolpus; Fig. 6B; cf. Guinot-Dumortier 1960: pl. VII, figs 40-41); male ab- dominal telson large and truncated oval (Figs 2F, 3F) (vs. small and triangular in Hypocolpus; cf. Guinot-Dumort- ier 1960: pl. IX, fig. 53, pl. X, fig. 55); G1 with a prom- inent, spoon-shaped distal lobe (Fig. 3G—J) (vs. G1 with a short, non-protruding distal lobe, inwardly curved and encircling in Hypocolpus; cf. Guinot-Dumortier 1960: pl. VI, figs 32-35). The new genus slightly resembles Psaumis Koss- mann, 1877, and Paractaeopsis Serene, 1984, but can be readily distinguished. Gothus can be easily distinguished from Psaumis by lack of erosive depressions across body (Fig. 1A) (vs. chelipeds, ambulatory legs, carapace with strong erosive depressions in Psaumis; Fig. 6E; cf. Serene 1984: pl. XVII, fig. E); front divided by a V-shaped notch (Figs 1C, 3A) (front divided by a narrow fissure in Psaumis, Fig. 6E; cf. Serene 1984: pl. XVIII, fig. E); anterolateral zse.pensoft.net 974 Yuan, Z.-M. et al.: Anew genus and species of Xanthidae crab from the South China sea Figure 6. Euxanthinae and Actaeodes species in comparative material. A. Rizalthus anconis Mendoza & PKL Ng, 2008, female; CW 4.2 mm, CL 2.7 mm, NS-MJ-2022-1457; B. Hypocolpus haanii Rathbun, 1909, 1 male, CW 45.3 mm, CL 34.2 mm, MBM286755; C. Euxanthus exsculptus (Herbst, 1790), 1 male, CW 52.6, CL 33.2 mm, MBM163793; D. Euxanthus huonii (Hombron & Jacquinot, 1846), CW 34.0 mm, CL 24.0 mm, NS-MJ-2022-1734; E. Psaumis cavipes (Dana, 1852), 1 male, CW 13.8 mm, CL 8.6 mm, aop01; F. Actaeodes mutatus Guinot, 1976, 1 female, CW 20.8 mm, CL 12.5 mm, BFO2; G. Actaeodes hirsutissimus (Ruppell, 1830), 1 male, CW 31.9 mm, CL 21.0 mm, MBM164298; H. Actaeodes tomentosus (H. Milne Edwards, 1834), 1 male, CW 35.8 mm, CL 22.5 mm, Xan041. Scale bar: 1 mm (A); 5 mm (E, F); 10 mm (B_D, G, F). zse.pensoft.net Zoosyst. Evol. 100 (3) 2024, 965-987 margin with four teeth, first tooth flattened, sometimes completely reduced to appear as three teeth (Figs 1A, C, 3A) (anterolateral margin with very flat teeth, except for fourth tooth at junction of anterior and posterior lateral margins, which is more prominent in Psaumis, Fig. 6E; cf. Serene 1984: pl. XVIII, fig. E). It can be distinguished from Paractaeopsis by anterolateral margin with four teeth, first tooth flattened, sometimes completely reduced to appear as three teeth (Figs 1A, C, 3A) (anterolateral margin with four well development teeth in Paractaeopsis, cf. Takeda and Miyake 1968: fig. 1a); carapace broad, approximately 1.5 times as wide as long, with a relatively flat dorsal sur- face (Figs 1A, C, 3A) (carapace narrower, with a width not exceeding 1.4 times the length, and dorsal surface convex both anteroposteriorly and laterally in Paractaeopsis;, cf. Serene 1984: pl. XVII, fig. E); carapace 2M region divided into two lobes (Figs 1A, C, 3A) (carapace 2M region di- vided into four lobes tn Paractaeopsis, cf. Takeda and Mi- yake 1968: fig. 1a); ambulatory legs comparatively slender (Figs 1A, 3D) (ambulatory legs very short and stout in Par- actaeopsis, cf. Takeda and Miyake 1968: fig. 1c). Given the above comparisons, the current species can- not be placed within any known genera, necessitating the establishment of a new genus. The main morphological characteristics comparing Gothus gen. nov. with closely related genera are listed in Table 2. A>) Gothus teemo sp. nov. https://zoobank.org/9A4FA 138-D3F0-4FC0-8687-844B52C5BA 15 Figs 1-5 Type material. Holotype. CHINA « 1 male; CW 3.7 mm, CL 2.6 mm; Triton Island, Xisha Islands; 15°46'52.61"N, 111°12'28.62"E; 5 m; 10 May. 2024; Ziming Yuan coll.; 2404189149; MBM287027. Paratypes. CHINA * 1 female; CW 3.2 mm, CL 2.2 mm; Meiji Reef, Nansha Islands; 9°52'57.47"N, 115°33'48.59"E; 27 Apr. 2023; Aiyang Wang, Bingq- in Liu coll.; 2304278379; MBM287026 « 1 male (de- calcified); CW 3.2 mm, CL 2.4 mm; Meiji Reef, Nan- Sha Islands; 9°53'1.15"N, 115°33'37.42"E; 27 Apr. 2023; Aiyang Wang, Bingqin Liu coll.; 2304278461; MBM287024 ¢ 1 male (partially crushed); CW 4 mm, CL 2.7 mm; Meiji Reef, Nansha Islands; 9°53'1.15"N, 115°33'37.42"E; 27 Apr. 2023; Aiyang Wang, Bingq- in Liu coll.; 2304278486; MBM287025 « 2 juveniles; CW 1.8—2.2 mm, CL 1.3-1.5 mm; Meiji Reef, Nansha Islands; 9°54'25.75"N, 115°29'49.44"E; 3 m; 6 May 2022; Ziming Yuan, Yuli Sun, Shaobo Ma coll.; NS- MJ-2022-1287; MBM287023 « 1 juvenile; CW 2 mm, CL 1.3 mm; Meiji Reef, Nansha Islands; 9°53'30.84"N, 115°34'22.05"E; 5 m; 11 Apr. 2024; Ziming Yuan coll.; 2404188048; MBM287022. Table 2. Comparison of the characters of Gothus gen. nov. and six related genera included in the subfamily Euxanthinae. Character Gothus gen. nov. Rizalthus Visayax Euxanthus Hypocolpus Psaumis Paractaeopsis carapace dorsal with round with large granules, with distinct or faint relatively with granules and _ densely covered with pearly surface granules, with surrounded by reticulate pattern = smooth, without setae with granules granules, clustered long short setae basally of fused granules well-developed scattered long setae or scattered granules. tubular setae short setae carapace with four without clearly absence of with four to six —_ anterolateral teeth with very flat with four anterolateral margin anterolateral defined developed anterolateral teeth underdeveloped anterolateral teeth, developed teeth, first tooth anterolateral teeth anterolateral teeth only fourth tooth anterolateral teeth flattened, posterior prominent three teeth well developed carapace non-concave concave concave concave concave concave non-concave posterolateral margin front not protruding, not protruding, not protruding, _ protruding, divided protruding, divided _not protruding, _ protruding, divided divided by a divided by a divided by a by anarrow fissure by a narrow fissure divided by anarrow _ by a V-shaped V-shaped notch V-shaped notch V-shaped notch fissure notch epistome central part central part not central part not central part central part central part unknown protruding protruding protruding or protruding protruding protruding slightly protruding subhepatic cavity absent absent absent absent present absent absent etched depressions absent present on thoracic present on absent present on thoracic present on absent sternum chelipeds, sternum chelipeds, ambulatory legs, ambulatory legs carapace, and and carapace thoracic sternum male telson broad, truncated — smaller, triangular smaller, semi smaller, triangular smaller, triangular smaller, semi- unknown oval circular circular cheliped carpus robust, sometimes — strongly expanded robust robust robust slightly robust robust slightly expanded and protruding ambulatory leg comparatively comparatively comparatively comparatively comparatively comparatively very short and slender slender slender slender slender slender stout male first gonopod slender, distal lobe slender, distal lobe robust, distal lobe slender, distal lobe slender, distal lobe slender, distal lobe robust, distal lobe prominent, spoon- prominent, spoon- prominent, nearly normprotruding, normprotruding, | prominent, spoon- prominent, nearly shaped, curved inwards, with long setae on inner subdistal part shaped, nearly straight, with long setae on inner subdistal part setae on Inner subdistal part straight, with long inwardly curved and encircling, with short setae on inner subdistal part inwardly curved shaped, nearly and encircling, with straight, with long long setae on inner setae on inner subdistal part subdistal part straight, with long setae on inner subdistal part zse.pensoft.net 976 Yuan, Z.-M. et al.: Anew genus and species of Xanthidae crab from the South China sea Description. Carapace (Figs 1, 3A) broader than long, CW about 1.5 times the CL, dorsal surface bearing round granules, regions well defined, 1M separated from 2M by shallow transverse groove; 2M indistinct divid- ed, lateral lobe with elevated pointed tuberosity; 3M distinct, undivided; 4M indistinct; 1L, 3L, 4L indistinct; 2L, 51, 6L distinct, with elevated sharp tuberosity each on 2L, 5L; 1P distinct, 2P indistinct, flat; 2M, 5L, and 6L regions each with a tuft of setae; front wide, about 0.4 times CW, not protruding, divided into two slightly triangular lobes by a V-shaped notch, a small pore visi- ble from front introduced from median notch (Fig. 1B), frontal lobes and dorsal inner orbital angle separated by shallow depression; eyestalks densely granulated; area behind outer orbital angle slightly concave, not form- ing a subhepatic cavity; anterolateral margin starting from subhepatic region; first tooth nearly completely reduced; subsequent three teeth developed; second and third teeth nearly equal; fourth tooth smaller; carapace widest at second tooth; posterolateral margin almost straight; subhepatic region densely granulated; posterior margin nearly straight. Epistome (Fig. 1B, E) central region with short me- dian projection on posterior margin pronounced; lateral regions with undulating posterior margins; maxilliped 3 (Figs 1B, E, 3B) granulated; ischium subrectangular; pre- senting submedian groove; merus subquadrate; anterior margin indented; external anteroexternal angle expanded. Antennule (Fig. 1B, E) folding transversely; basal seg- ment of antenna subrectangular; contacting ventral ex- ternal frontal margin and ventral internal orbital angle; antennal flagellum filling orbital hiatus. Chelipeds (Figs 2A, B, 3C) symmetrical; meri short; carpi robust, with square-shaped outward expansion, surface granulated, aggregated into nodules; palms dor- sally with three protuberances, outer and dorsal surfaces densely granulated; fingers elongated, with triangular teeth, tips sharp, crossing at extremities when closed; dorsal surface of movable finger with three granular ridges; outer surface of immovable finger with two granular ridges. Ambulatory legs (Figs 1A, D, 3D) meri flattened, P5 merus length about 3.6 times width of distal end, granulated dorsally and along anterior and posterior edges; carpi granulated dorsally and along anterior edge, dorsal surface with a grooved indentation near anterior edge; propodi granulated dorsally and along edges; dactyli elongated, margins armed with gran- ules and setae, terminal end chitinous, sharp, slight- ly curved backward, dactylo-propodal lock very weak and inconspicuous. Male thoracic sternum (Fig. 2C) with sternites 1 and 2 completely fused, suture between sternites 2 and 3 straight, complete, sternites 3 and 4 mostly fused, su- ture between them visible only at margins, sternites 3 short, sternite 4 with central longitudinal groove, tu- bercle of sterno-pleonal lock (press-button mechanism) zse.pensoft.net located on posterior of sternite 5. Male pleon (Figs 2C, E, 3F) narrow; pleonites 3 to 5 completely fused, lateral margins of pleonite 6 slightly concave, telson long and broad, width slightly greater than length, truncated oval, basal margin wider than terminal margin of pleonite 6; paired tufts of setae present on margins of middle part and terminal margin of pleonites 3—5 and terminal mar- gin of pleonite 6. Female pleon (Figs 2D, F, 3E) oval- shaped, margins of pleonite 6 slightly concave; telson triangular; vulva longitudinally ovate, located at upper of sternite 6, occupying anteromedial half, near sternites 5/6 (Fig. 2G). G1 (Fig. 3G, H, I, J) slender, distal lobe prominent but not excessively elongated, long setae on inner subdistal side, small spines on outer side. G2 (Fig. 3K, L) short, distal lobe elongated, slightly curved upwards. Live coloration. Overall white to coral pink in col- oration, carapace adorned with symmetrical black to brown stripes, ambulatory legs and chelipeds bear- ing stripes of similar coloration, anterior part of che- lipeds carpus red (Figs 4, 5). Fingers brownish-black, the coloration of immovable finger extending onto the palm along both the inner and outer surfaces in male (Fig. 2A, B). Etymology. The new species is named after Teemo, a character from the MOBA (Multiplayer Online Battle Arena) video game League of Legends. This character, modeled after a raccoon, has a fluffy, diminutive stat- ure with a brown and white intermingled fur coat. This alludes to the new species’ small size, densely covered short setae, and brown-striped coloration. Distribution. Currently known from the type locality at Triton Island, Xisha Islands (Paracel Islands), and Mei- ji Reef (Mischief Reef), Nansha Islands (Spratly Islands), it inhabits crevices in shallow coral reefs. Remarks. Apart from the members of the subfamily Euxanthinae already compared in the remarks of Gothus gen. nov., the species is most similar to Actaeodes con- sobrinus (A. Milne-Edwards, 1873). They share similar- ities in the carapace outline, the shape of the male pleon, and even in the pattern of the live coloration. However, G. teemo sp. nov. can be differentiated from A. consobri- nus by the following features: the first tooth on the an- terolateral margin of the carapace is completely reduced, almost invisible (Figs 1A, C, 3A) (vs. the first tooth low but still visible in A. consobrinus;, Figs 7A, B, 8A, 9A, B); carapace regions more pronounced, with tufts of se- tae (Figs 1C, 3A) (vs. carapace regions flatter, without tufts of setae in A. consobrinus, Figs 7A, B, 8A, 9A, B):; cheliped carpus with square-shaped outward expansion (Fig. 1A) (vs. cheliped carpus nearly spherical in A. con- sobrinus, Figs 7A, 8A, B); male pleon relatively broader, telson width slightly greater than length (Figs 2F, 3F) (vs. pleon very narrow, telson longer than wide in A. conso- brinus;, Figs 7D, 8E); G1 distal lobe shorter (Fig. 3G—J) (vs. G1 distal lobe significantly elongated in A. consobri- nus, Fig. 8F—G). Zoosyst. Evol. 100 (3) 2024, 965-987 Gothus consobrinus (A. Milne-Edwards, 1873), comb. nov. Figs 7-10 Actaea consobrina A. Milne-Edwards, 1873: 255; de Man, 1896: 503; Odhner, 1925: 67, pl. 4, fig. 14; Ward, 1933: 246; Sakai, 1939: 491, pl. 94, fig. 2; Tweedie, 1950: 118; Serene & Lang, 1959: 291, fig. 2, A1-A3; Guinot, 1967a: 260 Actaea suffuscula Rathbun, 1911: 220, pl. 17, figs 10-11; Ward, 1934: 18; Estampador, 1959: 81. Actaeodes consobrinus Guinot, 1967b: 561; Guinot, 1976: 246, pl. 15, fig. 5; Sakai, 1976: 448, pl. 158, fig. 3; Takeda & Miyake, 1976: 108; Serene, 1984: 133(key), 134(key), 135, pl. 18 C; Galil & Vannini, 1990: 37. Actaeodes consobrina Guinot, 1971a: 1072. Non Actaea consobrina Nobili, 1907: 390. = Pseudoliomera ruppellioides (Odhner, 1925). Material examined. CHINA ¢ 1 male; CW 3.0 mm, CL 1.9 mm; Yongshu Reef, Nansha Islands; 9°39'51.97"N, 113°0'S2.98"E; 10 m; 6 May 2022; Ziming Yuan, Yuli Sun, Shaobo Ma coll.; NS-YS-2022-1226 * 1 male; CW 7.6 mm, CL 5.2 mm; same collection data as for preced- ing; 14 May 2022; NS-YS-2022-1227 « 2 juveniles; CW 2.1-2.2 mm, CL 1.5—1.6 mm; same collection data as for preceding; NS-YS-2022-1263 « 1 male; CW 6.7 mm, CL 4.4 mm; same collection data as for preceding; NS- YS-2022-1336 1 juvenile; CW 2.5 mm, CL 1.7 mm; Mei- ji Reef, Nansha Islands; 9°52'38.19"N, 115°31'17.08"E; 8 m; 7 May 2022; NS-MJ-2022-1438 « 1 juvenile; CW 2.2 mm, CL 1.5 mm; same collection data as for pre- ceding but at 9°53'30.84"N, 115°34'22.05"E; 10 m; 10 May 2022; NS-MJ-2022-1789 « 1 female; CW 4.5 mm, CL 2.9 mm; Qilianyu, Xisha Islands; 16°58'04.2"N, 112°16'11.0"E; 10 m; 19 May 2022; XS-QL-2022-1014 ¢ 1 juvenile; CW 2.9 mm, CL 2.0 mm; Bei Reef, Xisha Islands; 17°07'00.5"N 111°32'03.2"E; 8 May 2023; Ai- yang Wang, Bingqin Liu coll.; 2305089358 « 1 male; not measured; Zhongsha Islands; 18—23 m; dead coral: 5 Jun. 2021; Geng Qin coll.; C13-5 « 1 male; not measured; same collection data as for preceding, 9 Jun. 2021; C57- 3 * 1 male; CW 5.4 mm, CL 3.6 mm; Zhongsha Islands; 15°53'10.5"N, 114°47'29.76"E, 20 m; 26 Jun. 2020; Wei Jiang, Geng Qin coll.; ZS233C07. Comparative material. Actaeodes mutatus Guinot, 1976 (Fig. 6F). CHINA * 1 male; Lingao, Hainan Island; 25 Nov. 2007; Xan074 * 1 female; Hainan Island; 2022: Xu Zhang coll.; BFO1 * 1 female; Phoenix Island, Sanya, Hainan Island; 2021; Xu Zhang coll.; BFO2. CW 14.8- 20.8 mm, CL 8.6—12.5 mm. Actaeodes hirsutissimus (Riippell, 1830) (Fig. 6G). CHINA * 3 males; Zhao Shu Island, Xisha Islands; 15 Apr. 1976; MBM164262 « 1 female; north of Dong Island, X1- sha Islands; 9 Jun. 1975; MBM164166 « 2 males, 3 ovig- erous females; Dong Island, Xisha Islands; 9 Jun. 1975; MBM164155 ¢ 1 male, 1 female, 3 juveniles; Northeast of Dong Island, Xisha Islands; 10 Jun. 1975; MBM164148 « Ot 4 males, 2 females; Rocky Island, Xisha Islands; 2—4 Jun. 1981; MBM164151 « 1 female; Dong Island, Xisha Is- lands; 28-30 May 1980; MBM164140 « 2 juveniles; Jin- qing Island, Xisha Islands; 10 Jul. 2019; MFO1 ¢ 2 males; E Xuan Port, Danzhou, Hainan Island; 7 Nov. 2021; Xan179« 1 male; Yuzhuo Reef, Xisha Islands; 9 Jul. 2019; MFO02 « 9 males, 9 females; Rocky Island, Xisha Islands; 9 May 1975; Xianqiu Ren coll.; MBM164298 « 8 males, 5 females, 2 juveniles; Coral Island, Xisha Islands; 19—23 May 1980; MBM164189 « 2 males, 4 females, 1 juvenile; Jinging Island, Xisha Islands; 9 May 1980; MBM164190 ¢ 1 female; Xian’e Reef, Nansha Islands; 12 May 1989; MBM164196 « 2 males, 2 females; Jinyin Island, X1- sha Islands; 14 May 1980; MBM164185 « 2 ovigerous females; Northeast of Dong Island, Xisha Islands; 10 Jun. 1975; MBM164261 « 5 males, 4 females; Jinging Island, Xisha Islands; 19 May 1981; MBM164225. CW 7.7-34.2 mm, CL 5.2—22 mm. Actaeodes tomentosus (H. Milne Edwards, 1834) (Fig. 6H). Cutna * 1 male; Wenchang, Hainan Island; 24 Jul. 2021; RFO1 ¢ 1 male; Xincun, Hainan Island; 29 Mar. 2008; Ping Lan, Yongqiang Wang coll.; MBM282509 « 3 males; Xiaodonghai, Hainan Island; 23 Mar. 2008; MBM282414 ¢ 4 males, 4 females; same collection data as for preceding; 25 Dec. 2007; MBM283216 * 9 males, 6 females; same collection data as for preceding; 24 Dec. 2007; Xan045, MBM283218 « 2 males, 1 female; same collection data as for preceding; 23 Mar. 2008; Wei Jiang coll.; Xan041 ¢ 1 fe- male; Langhua Reef, Xisha Islands; 11 May 2015; Xan126 ¢ 1 male; Houhai, Sanya, Hainan Island; 22 Mar. 2018; Xan048 ¢ 1 female; Dadonghai, Hainan Island; 2021; Xu Zhang coll.,; RFO3 ¢ 1 male; Sanya, Hainan Island; 2022: Xu Zhang coll.; RFO4 « 1 female; Sanya, Hainan Island; 20 Aug. 2019; Yunhao Pan coll.; RFO5 « 1 male; Yuzhuo Reef, Xisha Islands; 9 Jul. 2019; RFO6 « 1 male; Lingyang Reef, Xisha Islands; 11 Jul. 2019; RFO7 « 1 male; Yongxing Is- land, Xisha Islands; 27 Mar. 1980; MBM164194 « 1 female; Sanya Bay, Hainan Island; 22 Nov. 1990; MBM164492. CW 11.2-37.4 mm, CL 7.4-24.9 mm. Description. Carapace (Figs 7A, B, 8B, 9A, D, G) broader than long, CW about 1.5 times the CL, dorsal sur- face bearing round granules, granules interspersed with short pubescence; regions well defined, grooves wide and deep, 1M separated from 2M; 2M completely divided; 3M distinct, divided into three lobes; 4M distinct; 1L, 4L indistinct; 2L, 3L, 51, 6L distinct, 5L, 6L partially divid- ed; 1P, 2P distinct; front broad, about 0.3 times CW, not protruding, divided into two slightly triangular lobes by a wide and deep V-shaped notch, frontal lobes and dorsal inner orbital angle separated by shallow depression; eye- stalks densely granulated; Anterolateral margin divided into four teeth by narrow but sometimes opened fissures; first tooth extremely flattened, second tooth broader, sometimes obtuse, third tooth prominent, fourth tooth slightly smaller than third; carapace widest at third tooth; posterolateral margin almost straight; subhepatic region densely granulated; Posterior margin nearly straight. zse.pensoft.net 978 Yuan, Z.-M. et al.: Anew genus and species of Xanthidae crab from the South China sea Figure 7. Gothus consobrinus (A. Milne-Edwards, 1873), male, CW 6.7 mm, CL 4.4 mm, NS-YS-2022-1336. A. Dorsal habitus; B. Carapace; C. Frontal view; D. Thoracic sternites and pleon; E. Chelipeds. Scale bar: 2 mm. Epistome (Figs 7C, 9B, E, H) Central region with me- dian projection on posterior margin; lateral regions with undulating posterior margins. Maxilliped 3 (Figs 7C, 8B) granulated, ischium subrectangular, presenting submedi- an groove; merus subquadrate; anterior margin indented; anteroexternal angle square-shaped expanded. Antennule (Fig. 7C, 9B, E, H) folding transversely; basal segment of antenna subrectangular; contacting ventral external frontal margin and ventral internal orbital angle; antennal flagellum filling orbital hiatus. zse.pensoft.net Chelipeds (Figs 7E, 8C) symmetrical, meri short; carpi robust, nearly spherical, surface granulated, aggre- gated into nodules; outer and dorsal surfaces of palms densely granulated; fingers elongated, with triangular teeth, tips sharp, crossing at extremities when closed; dorsal surface of movable finger with three granular ridges; outer surface of immovable finger with two ridg- es. Fingers brownish-black, coloration of immovable finger extending onto palm along both inner and outer surfaces in male. Zoosyst. Evol. 100 (3) 2024, 965-987 979 5 \ Ese eae 9 a fa Figure 8. Gothus consobrinus (A. Milne-Edwards, 1873), male, CW 6.7 mm, CL 4.4 mm, NS-YS-2022-1336. A. Carapace; B. Maxilliped 3; C. Cheliped; D. Pereopod 5; E. Pleon; F. Left G1, ventral view; G. Left G1; H. Left G2, ventral view. Scale bar: 2 mm (A); 0.5 mm (B, F, H); 1 mm (C, D, E); 0.1 mm (G). zse.pensoft.net 980 Ambulatory legs (Figs 7A, 8D) with meri flattened, P5 merus length about 3 times as wide as distal end, gran- ulated dorsally and along anterior and posterior edges; carpi granulated dorsally and along anterior edge; dorsal surface with a grooved indentation near anterior edge; propodi granulated dorsally and along edges: dactyli elongated, margins armed with granules and setae, termi- nal end chitinous, sharp, slightly recurved, dactylo-prop- odal lock present. Male thoracic sternum (Fig. 7D) with sternites 1 and 2 completely fused, suture between sternites 2 and 3 straight, complete, sternites 3 and 4 mostly fused, suture between them visible only at margins, sternites 3 short, sternite 4 with central longitudinal groove, tubercle of sterno-pleonal lock (press-button mechanism) located on posterior of sternite 5. Male pleon (Figs 7D, 8E) very narrow; pleonites 3 to 5 completely fused; lateral margins of pleonite 6 slightly concave; telson long, broad, longer than wide; truncated oval; basal margin wider than termi- nal margin of pleonite 6. G1 (Fig. 8F-G) slender, distal lobe prominent, elon- gated, curved upwards, long setae on inner subdistal side, small spines on outer side. G2 (Fig. 8H) short, distal lobe elongated, slightly curved upwards. Live coloration. Overall white to ivory-colored, car- apace adorned with symmetrical black to brown stripes and orange spots, ambulatory legs and chelipeds bearing black to brown stripes, cheliped palm dorsal surface and anterior part of carpus sometimes coral pink (Fig. 10). Fingers brownish-black, coloration of immovable finger extending onto inner and outer surfaces of palm in male (Fig. 7E). Distribution. Distributed in the Zhongsha (=Maccles- field Bank), Xisha (=Paracel Islands), and Nansha Islands (=Spratly Islands) of the China Sea; widely found in the Indo-West Pacific, with the type locality at Upolu Island, inhabiting crevices in shallow coral reefs. Remarks. This report constitutes the first record of this species in the Chinese sea. Alphonse Milne-Edwards (1873: 255 [79]) briefly described “Actaea consobrina” from Upolu in present-day Samoa and provided the car- apace measurements of one specimen (CW 10 mm, CL 7 mm), though they did not indicate the sex of the specimen nor how many other specimens they examined. This spe- cies remained in the genus Acfaea until Guinot (1967b) transferred it to Actaeodes. As part of her revision of some Actaeinae genera, including Actaeodes, Guinot (1976: 246) examined two female specimens collected by A. Milne-Edwards and deposited in the MNHN (MP- B3885S from Upolu and a specimen without a collection number from “Samoa?”). She pointed out that based on the measurements (CW 10 mm, CL 7 mm), this specimen MP-B3885S could be the holotype of Actaeodes conso- brinus. For the purposes of this study, we consider this specimen to be typical of A. consobrinus and use it for our comparisons (Fig. 9A—C). It exhibits a nearly truncat- ed second anterolateral tooth with open fissures between zse.pensoft.net Yuan, Z.-M. et al.: Anew genus and species of Xanthidae crab from the South China sea the anterolateral teeth, which is also observed in some of the current specimens (Fig. 9G—I). Compared to the specimens from the China Sea, it has deeper grooves on the carapace, which may be attributed to growth-related differences considering its larger size. The other female individual (MNHN-IU-2024-3483) found together with this specimen is likely the one collected by A. Milne-Ed- wards that lacks a collection number (Guinot, 1976: 246; CW 8.5 mm, CL 6 mm), based on its measurements (CW 8.8 mm, CL 5.7 mm; Fig. 9D-F). This specimen possess- es triangular anterior lateral teeth and shallower grooves on the carapace (Fig. 9D-F). There are some issues regarding the classification of this species within its genus: Alphonse Milne-Edwards (1873) put the species in Actaea De Haan, 1833, and initially compared it with Actaea hirsutissimus (Rip- pell, 1830) (presently known as Actaeodes) and Actaea kraussi (Heller, 1860) (presently known as Banareia) and primarily considered it similar to the former. Sakai (1939) considered the species to be close to Paractaea tumulosa (Odhner, 1925). Guinot (1967b, 1976) op- posed the similarity to P. tumulosa but acknowledged its relationship with Actaeodes, and upon reviewing Actae- odes, Actaea consobrina was classified into the genus Actaeodes Dana, 1851, and supplemented its morpho- logical characteristics. In Guinot’s review (1976), the definition of Actaeodes includes the following characteristics: 1) carapace wide to very wide; 2) long anterolateral margins curving back over branchial regions, divided into lobes by fissures that extend as grooves into the subhepatic region; 3) very short posterolateral margins with a strong concavity that coapted against the last three pairs of ambulatory legs; 4) developed areolation of the dorsal surface with granular and pilosity lobules; 5). The frontal edge slopes down- ward with a central notch leading to the anterior tip of the epistome; the frontal lobes barely form a canopy above the antennules; 6) orbits round and relatively small, with specific fissures on supraorbital and exorbital edges; no infraorbital fissure 7) Equal and short chelipeds, with fin- gers either ending in a spoon-shaped tip or crossing at tips; 8) antenna fitting between front and orbit or with a closed orbit in Actaeodes semoni (Ortmann, 1894); 9) small and slightly depressed epistome, with the anterior tip projecting forward to join the anterior median groove of the dorsal face; 10) short ambulatory legs; 11) sub-he- patic region grooved; 12) thoracic sternite 4 traversed by two transverse grooves and two oblique grooves, and with a very clear longitudinal groove, hidden by telson; a median line present at levels of sternites 6, 7, and 8; 13) male pleon with fused pleonites 3-5, elongated and pro- jecting forward, featuring a median longitudinal swelling from 3 to 6 pleonites; 14) Gl with a tapered distal lobe adorned with relatively short bristles. Actaeodes currently comprises six species, among which the type species A. tomentosus, A. semoni (Ortmann, 1894), A. hirsutissimus (Ruppell, 1830), and Zoosyst. Evol. 100 (3) 2024, 965-987 981 Figure 9. Gothus consobrinus (A. Milne-Edwards, 1873). A-C. Female, CW 10.5 mm, CL 6.8 mm, MNHN-IU-2000-3885 (=MP- B3885S); D-F. Female, CW 8.8 mm, CL 5.7 mm, MNHN-IU-2024-3483; photographed by Sébastien Soubzmaigne; G—I. Female, CW 4.5 mm, CL 2.9 mm, XS-QL-2022-1014. Scale bar: 2 mm (A-F); 1 mm (G—I). A. mutatus Guinot, 1976 share a relatively similar appear- ance and match the description above. The most direct similarity is likely due to the very short posterolateral margins with a strong concavity that coapted against the last three pairs of ambulatory legs. However, A. conso- brinus and A. quinquelobatus Garth & Kim, 1983 exhibit morphologies that differ significantly and may not fit well within the genus Actaeodes. For the current species A. consobrinus, it indeed exhib- its several features similar to typical Actaeodes species, which mainly include a carapace with developed dorsal areolation with granular and setae, longer anterolateral margins and shorter posterolateral margins, symmetrical chelipeds with sharply crossing tips, an elongated male pleon, and a GI that is overall similar in morphology. However, this similarity 1s superficial, and there are some undeniable differences between A. consobrinus and typi- cal Actaeodes species. A. Milne-Edwards, in the original description, compared A. consobrinus with A. hirsutissi- mus, noting the absence of a pronounced concavity in its posterior margin. In current observations, the posterior margin of this species is almost straight (Figs 7A, B, 8A, 9A, D, F), which significantly deviates from Ac- taeodes (Fig. 6F—-H; cf. Guinot 1976: pl. XV, figs 1-4). Furthermore, the morphology of the thoracic sternum in the current species markedly differs from Actaeodes, with its third sternite being very short (Fig. 7D) (vs. elongat- ed third sternite in Actaeodes; cf. Guinot 1976: fig. 41C) and the fourth sternite lacking oblique grooves (Fig. 7D) (fourth thoracic sternite of Actaeodes traversed by two transverse grooves and two oblique grooves; cf. Guinot 1976: fig. 41C). Other differences include A. consobrinus having an elongated pleon that barely extends beyond the coxo-sternal condyles of pereiopod 1 (Fig. 7D) (vs. ple- on being significantly elongated, clearly surpassing the coxo-sternal condyles of pereiopod 1 in Actaeodes, cf. Guinot 1976: fig. 41C); like other species in Actaeodes, A. consobrinus has an elongated telson, but its overall shape is truncate-oval, with relatively arcuate lateral edg- es (Fig. 7D) (vs. triangular telson with converging lat- eral edges in Actaeodes, cf. Guinot 1976: fig. 41C); A. consobrinus has the first tooth flattened and the subse- zse.pensoft.net Yuan, Z.-M. et al.: Anew genus and species of Xanthidae crab from the South China sea Figure 10. Gothus consobrinus (A. Milne-Edwards, 1873). A. Male, CW 6.7 mm, CL 4.4 mm, NS-YS-2022-1336; B. Female, CW 4.5mm, CL 2.9 mm, XS-QL-2022-1014, displaying live coloration. Scale bar: 2 mm. zse.pensoft.net Zoosyst. Evol. 100 (3) 2024, 965-987 quent three teeth prominent (Figs 7A, B, 8A, 9A, D, F) (vs. anterolateral margin divided into four distinct but not very prominent lobes in Actaeodes; Fig. 6F—H; cf. Guinot 1976: pl. XV, figs 1-4); the cheliped carpus is more ro- bust in A. consobrinus (Figs 7A, 9A, D, F) (vs. propor- tionally more slender carpus in Actaeodes, Fig. 6F—H; cf. Guinot 1976: pl. XV, figs 1-4). It is worth mentioning that although body color is generally not used as a basis for defining genera within the family Xanthidae, the vibrant and high-contrast living coloration of A. consobrinus 1s also quite unique in Actaeodes (Fig. 10). Based on the aforementioned reasons, A. consobrinus is not suitable for placement within the genus Actaeodes. Another genus worth considering is Meractaea Serene, 1984, characterized by almost straight posterolat- eral margins, developed areolation on the dorsal surface of the carapace, and four underdeveloped small teeth on the anterolateral margins, all of which are similar to the current species. However, there are also differences be- tween this genus and A. consobrinus, including an almost straight, quadrilobate frontal margin with a rounded cen- tral notch (cf. Serene 1984: pl. XIX, fig. C) (vs. front not very prominent but not straight, divided by a V-shaped notch into two inclined rounded lobes in A. consobri- nus, Figs 7A, B, 8A, 9A, D, F); markedly slender am- bulatory legs (cf. Serene 1984: pl. XIX, fig. C) (vs. flat and robust ambulatory legs in A. consobrinus, Figs 7A, 8D); a completely smooth dorsal surface of the carapace with irregularly sized granules, sometimes connected (cf. Serene 1984: pl. XIX, fig. C) (vs. carapace dorsal surface with setae, regularly sized granules, never connected in A. consobrinus, Figs 7A, B, 8A, 9A, D, F); G1 distal lobe slightly curved outward (cf. Serene 1984: fig. 63) (vs. G1 distal lobe curved inward in A. consobrinus; Fig. 8F—G). Considering these significant differences, A. consobrinus also cannot be placed within this genus. Compared with the species of Actaeodes and Merac- taea, A. consobrinus 1s actually more closely related to G. teemo. Beyond the most noticeable similarity in vibrant living coloration, both share similar carapace contours, flattened first anterolateral teeth, robust cheliped carpus, similar states of thoracic sternum, and special male ab- dominal morphology, particularly the truncate-oval tel- son (see the comparison in the remarks of G. teemo). We believe that placing this species into the current new ge- nus and new combination is more appropriate. Regarding the status of A. quinquelobatus, in the ab- sence of specimens, we hereby present some limited que- ries. Similar to the new combination G. consobrinus, the morphology of A. quinquelobatus also appears to devi- ate from the definition of Actaeodes sensu stricto, fea- turing 5 instead of 4 anterolateral teeth and possessing non-concave posterior margins (cf. Garth and Kim 1983: fig. 5A). As Garth and Kim (1983) noted, A. quinquelo- batus has carapace partitioning similar to G. consobrinus. However, current evidence does not affirm its placement within the genus Gothus, given it has 5 anterolateral teeth 983 (cf. Garth and Kim 1983: fig. 5A) (vs. 3 or 4 in Gothus, Figs 1C, 7A), and the carapace and chelae exhibit a mul- titude of developed nodules (cf. Garth and Kim 1983: fig. SA, B) (vs. surfaces have granules but lack nodules in Gothus; Figs 1A, 7A). Further examination is necessary to confirm its taxonomic status. Molecular data analysis To further confirm the taxonomic status of the new genus, new species, and new combination, we conducted mo- lecular phylogenetic studies. The topologies of the ML and BI phylogenetic trees differed, yet both consistently supported the formation of a high-confidence clade com- prising G. teemo and G. consobrinus (100/100), distinct from any related genera (Fig. 11). The species delimita- tion based on both ABGD and bPTP methods has validat- ed the new species’ legitimacy (Fig. 12). In the previous study of Lai et al. (2011), the genera Euxanthus, Hepatoporus Serene, 1984, Hypocolpus, Olenothus Ng, 2002, Rizalthus, Visayax, and Psaumis were grouped into a monophyletic clade, referred to as Eux 1. Similar monophyletic clades were observed in the molecular systematic studies of the Xanthoidea by Mendoza et al. (2022), with the addition of the genus Paractaeopsis. This clade has been recognized as the Euxanthinae sensu stricto. However, in current research, neither phylogenetic tree supports the monophyly of Eu- xanthinae sensu stricto. In the ML tree, Gothus clustered with the subfamily Liomerinae Sakai, 1976, but with low bootstrap support (BS=67), and some species of the ge- nus Xanthias Rathbun, 1897, disrupted the monophyly of Euxanthinae sensu stricto. In the BI tree, Gothus, certain species of Xanthias, and part of the Euxanthinae sensu stricto species clustered together with low posterior prob- ability (PP=51), also disrupting the monophyly of the previous Euxanthinae sensu stricto species. In current re- search, the scope of Euxanthinae sensu stricto may need to be further narrowed, excluding Rizalthus and Visayax. Discussion The results of integrative taxonomy suggest that G. teemo and G. consobrinus together constitute a distinct genus within the family Xanthidae. Despite molecular phylogenetic results indicating that Gothus does not form a stable monophyletic group with any related subfamily and is not well integrated into Euxanthinae sensu stricto, we have nonetheless decided to tentatively maintain its placement within Euxanthinae, albeit with reservations. This decision 1s based on the spe- cies’ close morphological congruence with the traditional understanding of Euxanthinae, and molecular systematic studies have also shown it to have a closer phylogenetic relationship with Euxanthinae sensu stricto. zse.pensoft.net 984 Yuan, Z.-M. et al.: Anew genus and species of Xanthidae crab from the South China sea A =: Actaeodes hirsutissimus | Actaeodes = Actaeodes tomentosus Gothus consobrinus comb. nov. | Gothus gen. nov Gothus teemo sp. nov. . Liomera cinctimana Paratergatis longimanus = Xanthias latifrons ‘i a Sunttinr jodinece | “Xanthias” 57 a Psauiis cavipes j , Paractaeopsis quadriareolata 67 | Liomerinae 75) Hepatoporus orientalis Olenothus uogi tal a Hypocolpus pararugosus Hypocolpus abbotti 54 63 700 Euxanthus ruali Euxanthinae mn Euxanthus exsculptus Euxanthus herdmani | ear Hypocolpus diverticulatus Fi Euxanthus huoniti Rizalthus anconis — Visayax osteodictyon Demania intermedia ba Neoxanthias michelae _ —— Puleratis reticulatus Liagore rubromaculata 98 100 7 —— Neoliomera striata Pseudoliomera granosimana Pseudoliomera speciosa 100 TT Paractaea rufopunctat 70 — —— Gaillardiellus ruppelli Atergatis integerrimus 100 700 Platypodia pseudogranulosa Zosimus aeneus 8 aa Novactaea bella —— Xanthias canaliculatus Forestiana depressa Zalasius sakaii er Banareis nobili sus and, MS 10 2 22 Macromedaeus erassmanus Chlorodieila nigra eT Cymo quadrilobatus Xanthidae Actaea pura 98 73 98 Lybia tessellata 700 — Menippe rumphii Eriphia gonagra Outgroup i B Actaeodes hirsutissimus ee Actaeodes tomentosus Demania intermedia 100 aa Neoxanthias michelae Pulcratis reticulatus Liagore rubromaculata Gothus consobrinus comb. nov. | Gothus gen. nov. Gothus teemo sp. nov. Bs aT Spat te latifrons | “Nanthias” “ anthias joanneae Psaumis cavipes 74 aractaeopsis quadriareolata Hepatoporus orientalis Olenothus uogi 100 Hypecolpus abbotti 50 Hypocolpus pararugosus : 78 ao Euxanthus ruali Euxanthinae Euxanthus exsculptus Euxanthus herdmani Hypocolpus diverticulatus Euxanthus huonii Rizalthus anconis Visayax osteedictyon Liomera cinctimana Paratergatis longimanus Pseudoliomera speciosa 700 Paractaea rufopunctat [ 100 x - 7 81 Gaillardiellus ruppelli Atergatis integerrimus 700 5 Platypodia pseudogranulosa Zosimus aeneus 700 - Neoliomera striata 5 Pseudoliomera granosimana Xanthidae Novactaea bella Actaea pura | Actaeodes 100 100 90 63 100 100 | Liomerinae 100 Zalasius sakaii_ eal - Banareia nobili Forestiana depressa Xanthias canaliculatus s Etisus anaglyptus _ 100 Macromedaeus crassimanus Chlorodiella nigra Cymo quadrilobatus Lybia tessellata 100 100 Eriphia gonagra Menippe rumphii Outgroup | 0.05 Figure 11. Phylogenetic relationships inferred from combined 12S, 16S, COI, and H3 sequences among Gothus gen. nov. and re- lated species in Xanthidae, analyzed by Bayesian Inference (BI) and maximum likelihood (ML) analyses. A. BI tree, with posterior probabilities (PP) labeled; B. ML tree, with bootstrap replications (BS) labeled; values below 50 are hidden. Most data are derived from Lai et al. (2011) and Mendoza et al. (2022), as shown in Table 1. Mendoza et al. (2022) had already pointed out the may further corroborate the taxonomic status of the non-monophyly of the Euxanthinae subfamily. Our new genus and the internal relationships within the study also challenges the monophyly of the primary subfamily Euxanthinae. monophyletic group within the subfamily as identified Current research suggests that for complex and diverse in the previous research, or the previous Euxanthinae taxonomic groups like the family Xanthidae, potential- sensu stricto. Considering the limited number of mo- _ ly undiscovered taxa could offer new insights into their lecular markers currently used, unaccounted species, classification systems. The integration of morphological and the potential impact of incomplete lineage sort- and molecular phylogenetic analyses may aid in further ing (ILS), the inclusion of additional taxa and data taxonomic revisions of these groups. zse.pensoft.net Zoosyst. Evol. 100 (3) 2024, 965-987 79 99 99 99 93 97 - 100 100 92 96 55 100 0.02 985 bPTP ~ Hypocolpus abbotti Olenothus uogi - Hypocolpus pararugosus ~ Rizalthus anconis Visayax osteodictyon - Hepatoporus orientalis - Psaumis cavipes ~ Paractaeopsis quadriareolata ~ Euxanthus exsculptus ~ Buxanthus ruali - Euxanthus herdmani Aypocolpus diverticulatus ~ Euxanthus huonii ~ Gothus consobrinus NS-YS-2022-1336 ~ Gothus consobrinus NS-MJ-2022-1438 -- Gothus consobrinus XS-QL-2022-1014 Gothus teemo sp. nov. ~ Cymo quadrilobatus ; outgroup ~ Lybia tessellata Figure 12. Bayesian inference (BI) phylogenic tree based on COI showing the phylogenetic relationship between Gothus teemo sp. nov., G. consobrinus, and related Euxanthinae species, with bootstrap replications (BS) labeled and values below 50 not shown. The results of automated barcode gap discovery (ABGD) and Bayesian implementation of the Poisson tree processes (BPTP) species delimitation methods are shown on the right of the figure; each circle or capsule shape represents one species. Acknowledgements The authors express their gratitude to Yuli Sun, Shaobo Ma, Aiyang Wang, and Bingqin Liu for their significant contributions to the sample collection. The authors would also like to thank Xu Zhang and Yunhao Pan for pro- viding samples. The authors also wish to acknowledge and thank Fei Gao for the exquisite artistic illustrations provided for the new species. 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