The Laevicaudata (smooth clam shrimp) are a small group of freshwater bivalved branchiopod crustaceans in need of taxonomic revision. Here the extant Laevicaudata are defined and diagnosed according to modern standards, and synapomorphies are listed, discussed, and illustrated. A catalogue of the Laevicaudata is presented with synonyms and some taxa are partially revised. One hundred and three recent laevicaudatan taxa are presented, of which 39 are considered valid species. Chresonyms are provided for taxa redescribed according to modern standards. Furthermore we designate a neotype for Lynceus brachyurus Müller, 1776. This species catalogue will provide a basis for further taxonomic revision and phylogenetic work within the Laevicaudata.