The Oxyporus species from the Malay Peninsula are revised. The following two species are recognised: O. pendleburyi (= O. intermedius new synonym; O. atratus new synonym) and O. cameronianus, new species. All species are (re-)described with illustrations of the taxonomically important characters and photographs of their habitus.

Twenty-one species of Thinophilus Wahlberg, 1844 are recorded from mangroves and fresh water habitats in Singapore. Fourteen new species for science are described and illustrated from Singapore: Thinophilus apicatus sp. nov., Thinophilus chaetulosus sp. nov., Thinophilus comatus sp. nov., Thinophilus evenhuisi sp. nov., Thinophilus lenachanae sp. nov., Thinophilus meieri Grootaert & Evenhuis sp. nov., Thinophilus minor sp. nov., Thinophilus nigrilineatus sp. nov., Thinophilus pallitarsis sp. nov., Thinophilus puniamoorthyae sp. nov., Thinophilus simplex sp. nov., Thinophilus singaporensis sp. nov., Thinophilus superbus sp. nov., and Thinophilus yeoi sp. nov. Following four species are reported for the first time from Singapore: Thinophilus nitens Grootaert & Meuffels, 2001; Thinophilus parmatus Grootaert & Meuffels, 2001; Thinophilus setiventris Grootaert & Meuffels, 2001; and Thinophilus spinatus Samoh et al., 2017. New data are given on Thinophilus asiobates Evenhuis & Grootaert, 2002; Thinophilus longicilia Evenhuis & Grootaert, 2002; Thinophilus murphyi Evenhuis & Grootaert, 2002; and the non-Singaporean Thinophilus clavatus Zhu, Yang & Masunaga, 2006; Thinophilus parvulus Samoh et al., 2017; and Thinophilus variabilis Samoh et al., 2017. Thinophilus peninsularis Parent, 1935 from peninsular Malaysia is re-described. A key is provided for the male Thinophilus of the Malay Peninsula (southern Thailand, peninsular Malaysia including Singapore). NGS barcodes (313 base pairs) are given for most of the species. Only three species do occur in terrestrial freshwater habitats: T. singaporensis sp. nov. is exclusive for these habitats while T. nitens and T. setiventris are ubiquitous flies with a preference for anthropogenic habitats such as drains and inundated fall land. The other 18 species are exclusive in mangroves.

Twenty-one species of Thinophilus Wahlberg, 1844 are recorded from mangroves and fresh water habitats in Singapore. Fourteen new species for science are described and illustrated from Singapore: Thinophilus apicatus sp. nov., Thinophilus chaetulosus sp. nov., Thinophilus comatus sp. nov., Thinophilus evenhuisi sp. nov., Thinophilus lenachanae sp. nov., Thinophilus meieri Grootaert & Evenhuis sp. nov., Thinophilus minor sp. nov., Thinophilus nigrilineatus sp. nov., Thinophilus pallitarsis sp. nov., Thinophilus puniamoorthyae sp. nov., Thinophilus simplex sp. nov., Thinophilus singaporensis sp. nov., Thinophilus superbus sp. nov., and Thinophilusyeoi sp. nov. Following four species are reported for the first time from Singapore: Thinophilus nitens Grootaert & Meuffels, 2001; Thinophilus parmatus Grootaert & Meuffels, 2001; Thinophilus setiventris Grootaert & Meuffels, 2001; and Thinophilus spinatus Samoh et al., 2017. New data are given on Thinophilus asiobates Evenhuis & Grootaert, 2002; Thinophilus longicilia Evenhuis & Grootaert, 2002; Thinophilus murphyi Evenhuis & Grootaert, 2002; and the non-Singaporean Thinophilus clavatus Zhu, Yang & Masunaga, 2006; Thinophilus parvulus Samoh et al., 2017; and Thinophilus variabilis Samoh et al., 2017. Thinophilus peninsularis Parent, 1935 from peninsular Malaysia is re-described. A key is provided for the male Thinophilus of the Malay Peninsula (southern Thailand, peninsular Malaysia including Singapore). NGS barcodes (313 base pairs) are given for most of the species. Only three species do occur in terrestrial freshwater habitats: T. singaporensis sp. nov. is exclusive for these habitats while T. nitens and T. setiventris are ubiquitous flies with a preference for anthropogenic habitats such as drains and inundated fall land. The other 18 species are exclusive in mangroves

Opinions and declarations Rendered by the International Commission on Zoological Nomenclature

The taxonomy of spider crabs of the genus Maja Lamarck, 1801, is revised, and a total of 36 species in 10 genera are now recognised from the eastern Atlantic, Mediterranean and Indo-West Pacific. The present revision describes seven genera and 17 species as new. Two genera previously synonymised under Maja: Paramaya De Haan, 1837, and Paramaja Kubo, 1936, are here treated as valid taxa. The confused nomenclature of Cancer cornutus Linnaeus, 1758, is resolved, and the name replaces Maja capensis Ortmann, 1894, and Mamaia queketti Stebbing, 1908.