The Maldanidae annelid worms are reviewed and the phylogenetic relationships of their subgroups provided, based on Hennigian principles and maximum parsimony. Characters were coded as binary and multistate (transformation series). We used 33 terminal taxa (species), and 50 characters. Characters were treated as unordered and of equal weight, and analysis was run in TNT. Three equally most-parsimonious trees were obtained with heuristic searches, with lengths of 64 steps; CI = 0.95, and RI = 0.98. The monophyly of Maldanidae was supported with 100% of bootstrap and jackknife values. As a result of our analysis, Arenicolidae remains the sister-group of Maldanidae, and both should be referred to Maldanomorpha. Maldanidae was supported by the following synapomorphies: dorsal prostomium; prostomium keel-shaped and fused to peristomium; torus globose behind median chaetigers; median chaetigers greatly elongated; number of pre-anal segments reduced. The subfamily Bogueinae was not monophyletic; Boguea and Boguella were included within Rhodininae. Clymenura, previously included in the Clymenurinae, was included within Euclymeninae. The taxa Notoproctinae, Maldaninae, Nicomachinae and Euclymeninae were grouped in the Maldanoplaca, a new taxon. Eight further new clades have been found, but were not named.
