Zootaxa 3572: 63–68 (2012) www.mapress.com / zootaxa/ Copyright © 2012 · Magnolia Press ISSN 1175-5326 (print edition) Article ZOOTAXA ISSN 1175-5334 (online edition) urn:lsid:zoobank.org:pub:B31F6A0F-47B9-41A4-90DE-A59EAB76B373 Establishment of a new genus for Cyclograpsus lophopus Nobili, 1905, within Sesarmidae Dana, 1851 (Crustacea: Decapoda: Brachyura) TOHRU NARUSE1,3 & NGAN KEE NG2 1 Tropical Biosphere Research Center, Iriomote Station, University of the Ryukyus, 870 Uehara, Taketomi, Okinawa 907-1541, Japan. E-mail: naruse@lab.u-ryukyu.ac.jp 2 Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543. Republic of Singapore. Email: ngankee@nus.edu.sg 3 Corresponding author Abstract The examination of the type series of the poorly known Cyclograpsus lophopus Nobili, 1905, which was originally placed in the varunid genus, Cyclograpsus H. Milne Edwards, 1837, has revealed that it belongs instead to the family Sesarmidae Dana, 1851. A new genus is also described for C. lophopus because of its very distinct morphological characters, e.g. entire and nearly circular contour of the carapace with trigonal ocular peduncles, and short and flattened ambulatory legs. Key words: Cyclograpsus lophopus Nobili, 1905, Cyclorma gen. nov., Sesarmidae, Varunidae, taxonomy Introduction Cyclograpsus H. Milne Edwards, 1837, had long been placed in the family Sesarmidae Dana, 1851. Recent larval studies and molecular phylogenetic researches suggested, however, that Cyclograpsus and its allied genera are phylogenetically closer to the family Varunidae H. Milne Edwards, 1853 (see Schubart & Cuesta 1998; Schubart et al. 2000, 2002, 2006; Kitaura et al. 2002; Davie 2002). Davie (2002) resurrected Cyclograpsacea H. Milne Edwards, 1853, as a subfamily within Varunidae to accommodate Cyclograpsus H. Milne Edwards, 1837, Chasmagnathus De Haan, 1833, Helicana K. Sakai & Yatsuzuka, 1980, Helice De Haan, 1833, Helograpsus Campbell & Griffin, 1966, Metaplax H. Milne Edwards, 1852, and Paragrapsus H. Milne Edwards, 1853. This arrangement was followed in the lists of Ng et al. (2008) and De Grave et al. (2009). Cyclograpsus lophopus Nobili, 1905 (Figs. 1–3), has been one of the least studied among the 21 known species of Cyclograpsus. Although Nobili (1905, 1906) described and photographed the type specimens, the material is not known to have been subsequently studied. Work at the Muséum national d’Histoire naturelle, Paris (MNHN) provided an opportunity to examine the type specimens of this species, which resulted in the revision of its placement as a new genus in the family Sesarmidae Dana, 1851. Measurements refer to carapace length × carapace width (in mm). The material examined is deposited in the Muséum national d’Histoire naturelle, Paris (MNHN). Taxonomy Family Sesarmidae Dana, 1851 Cyclorma gen. nov. Type species. Cyclograpsus lophopus Nobili, 1905, by monotypy. Accepted by P. Castro: 29 Oct. 2012; published: 5 Dec. 2012 63