Phylogeny of flatfishes (Pleuronectiformes): comparisons and contradictions of molecular and morpho-anatomical data

Several species of flatfishes (Pleuronectiformes) have been studied by isoenzyme electrophoresis and DNA/DNA hybridization to establish the evolutionary relationships of this group of fishes. This molecular data-based phylogeny has been compared to previously described phylogenies based on morpho-anatomical criteria. A number of discrepancies are observed and discussed. The high degree of genetic divergence observed within the families of Pleuronectiformes indicates that their origin seems to be much older than suggested by their striking morphological similarity.