The authors take into consideration general morphological analogies of the skeleton, coating of scales, and dentition that exist between the Pycnodontiformes and the Platysomiformes. Through analysis of new fossil samples, the authors establish that the characters showing similarities between the two groups are at least the following: (i) structure of vertebrae, (ii) post-abdominal bone, (iii) squamation reduced to bar-scale; furthermore, the structure and arrangement of the teeth is also compared between the two groups. The existence of these anatomical and structural analogies allow us to re-propose the opinion by earlier authors (Agassiz, Egerton, Young, Stensiö, Berg, Gardner) that the Paleozoic ancestors of the Pycnodontiformes would have had close anatomical, structural and ecological affinities to those of some fish close to the Platysomiformes.