Marine crabs new to Singapore, with a description of a new species of intertidal xanthid crab of the genus Macromedaeus Ward, 1942 (Crustacea: Decapoda: Brachyura)

Four species of marine crab (Brachyura) are reported for the first time from Singapore. Three of these have been previously reported from other localities in the Indo-West Pacific region, while one is a new species described herein. The camptandriid crab, Exagorium fidelisi Naruse, Chung & Tangah, 2015, originally described from northeastern Sabah, Malaysia, is reported from the mangroves of northern Singapore. Two xanthid crabs are newly recorded as well: Hepatoporus guinotae (Zarenkov, 1971) and Medaeops edwardsi Guinot, 1967, previously described from the Red Sea and Indian Ocean, respectively. Another xanthid crab, Macromedaeus adelus, new species, is described from the intertidal areas of Singapore. It is most similar to M. distinguendus (De Haan, 1835) and M. voeltzkowi (Lenz, 1905), primarily in having a distinctly areolated and granular carapace and having four teeth on the carapace anterolateral margin. It can, however, be distinguished from congeners by morphological features of the carapace, chelipeds, ambulatory legs, and the male first gonopods.