In 1993, Chapleau proposed the first comprehensive cladistic work on interfamilial relationships of flatfishes (order Pleuronectiformes) based on anatomical data. This work has been, and still remains, a cornerstone for phylogenetic works dedicated to flatfishes. Nevertheless, this valuable work lacked important elements of the current knowledge associated with flatfish outgroups and suffered from scarcity of data for some characters. We propose here the results of a new analysis of Chapleau’s matrix with reexamination of some characters (e.g. recessus orbitalis) and addition of two fossil genera (Heteronectes and Amphistium), plus two extant genera as outgroups, chosen on the basis of recent molecular analyses. This reassessment leaves the monophyly of the Pleuronectiformes ambiguous while the interrelationships within flatfishes proposed by Chapleau are not significantly modified. Moreover, the polarity of one character (structure of the first anal-fin pterygiophore) is reviewed and enlightens differently the first steps of the evolution of flatfishes.