Taxonomic revision of the genera Achiroides, Brachirus, Dexillus, and Paradicula (Pleuronectiformes: Soleidae)

The objective of this study was to taxonomically revise the 41 nominal species found within the Brachirus species complex (Order Pleuronectiformes; Family Soleidae). This complex is recognizable by a combination of characters: the structure of the supracranial portion of the dorsal fin which lack pterigiophores with their proximal ends directly over the cranium, by the joined dorsal, anal and caudal fins, and by the anterior tip of the dorsal fin almost reaching the upper jaw. This revision is based on the morphological and meristic examination of 34 type and 717 non-type specimens for all available nominal species. The type material was examined for twenty species. The remaining species were assessed from the original type description. It was found that the Brachirus species complex is made up of four genera including 19 valid species: Brachirus (14), Achiroides (1), Dexillus (3), and Paradicula (1). Eight of the nominal species do not belong to the Brachirus species complex and have been removed from the scope of this study. Achiroides, characterized by the rudimentary pectoral fins, contains a single valid species, A. melanorhynchus (Bleeker 1851) and three synonyms (Synaptura aenea Smith 1931, Anisochirus harmandi Sauvage 1878, and Plagusia leucorhynchos Bleeker 1851). Dexillus , characterized by the close proximity of the eyes, contains three valid species: D. macrolepis (Bleeker 1858), D. megalepidoura (Fowler 1934), and D. muelleri (Steindachner 1879). D. muelleri is a senior synonym of the nominal species Synaptura arafurensis Gunther 1880. Paradicula, unique in having the gill openings restricted to the base of the pectoral fins, contains a single valid species, P. setifer Paradice & Whitley 1927. The remaining Brachirus species cannot yet be defined as being monophyletic. Brachirus contains 14 valid species: B. aspilos (Bleeker 1852) (synonyms: Synaptura heterolepis Bleeker 1856, S. marmorata Bleeker 1853, and S. sorsongonensis Evermann & Seale 1907), B. sundaicus (synonyms: Bleeker 1870--75) (Synaptura cinerea De Vis 1883 and S. nigra MacLeay,1880), B. selheimi (Macleay 1882) (synonyms: B. salinarum Ogilby 1910, and Synaptura villosus Weber 1907), B. foliacea (Gunther 1862) (synonym: Synaptura filamentosa Sauvage 1878), B. siamensis (Sauvage 1878) (synonyms: Synaptura krempfi Durand 1940 and Chabanaudetta smithi Joglekar 1971), B. breviceps Ogilby 1910, B. cinerascens (Gunther 1862), B. fitzroiensis (De Vis 1882), B. orientalis (Bloch & Schneider 1801), B. pan (Hamilton 1822), B. panoides (Bleeker 1851), B. dicholepis Peters 1877, B. swinhonis Steindachner 1867, and B. canus Gray 1854. An identification key of valid species belonging to the Brachirus species complex is provided.