The systematics of the genus Syncomistes Vari, 1978 endemic to freshwater habitats of remote northwestern Australia, is reviewed in light of recent collections in the region and a fine scale molecular study of the group that identified new taxa. Based primarily on external morphology, seven taxa are described as new: Syncomistes bonapartensis sp. nov., S. carcharus sp. nov., S. dilliensis sp. nov., S. holsworthi sp. nov., S. moranensis sp. nov., S. wunambal sp. nov. and S. versicolor sp. nov. The species complexes Syncomistes butleri Vari, 1978 and S. trigonicus Vari, 1978 are resolved and redescribed, and S. kimberleyensis Vari, 1978 and S. rastellus Vari & Hutchins, 1978 are redescribed based on juvenile and adult specimens. Finally, a neotype is provided for S. trigonicus sensu stricto in place of the destroyed holotype. Meristic and morphometric data are collected and analysed for the entire genus. Syncomistes have a broad range of meristic and morphometric character differences between species, and juveniles and adults, as well as variations in colour. The head, particularly feeding structures such as the jaw and dentition, were found to be the most important morphological features in discriminating between taxa. Some characters undergo distinct ontogenetic shifts in form, which are discussed. Of note, four of the new species, and seven from the entire genus, are narrow-range endemics, each found in single river systems, and are thus of conservation concern.
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