: ci:v': -":^^- ' ;■;•■. 151 



relationships). However, Howes based his cladogram on the degree of vertebral 

 fusion, structure of the swimbladder, and the ESA, based primarily on data obtained 

 from Chardon (1968), to demonstrate how misleading a phylogenetic hypothesis can 

 be if based on relatively few weighted characters. In the case of each putatively 

 derived character state, Howes (1983) was able to provide evidence that conflicted 

 with some of the relationships suggested by his cladogram. In the case of taxa with 

 an ESA, Howes noted that no other groups except the neotropical doradoids 

 (although he erroneously excluded ageneiosids) had epioccipitals contacting the 

 vertebral parapophyses. Howes (1983) repeated the suggestion made by Alexander 

 (1964) that the ESA may have been independently derived in several lineages. 

 Moreover, Howes presented evidence to support the idea that increased vertebral 

 fusion and swimbladder encapsulation has occurred independently in two or more 

 lineages. In spite of his detailed arguments, Howes (1983) was unable to provide 

 any significant hypotheses of relationships outside of the Hypophthalmidae and 

 Pimelodidae. , ?*' -'^^ 



Convergence of an ESA suggested by Alexander (1964) and Howes (1983) 

 was apparently not seriously considered by Royero (1987) and Curtan (1989), both 

 of whom invoked the presence of an ESA as a synapomorphy of some or all of the 

 famiUes listed at the beginning of the previous paragraph. Ferraris (1988) was more 

 cautious in interpreting the taxonomic distribution of an ESA; he used it only to 

 define doradids, auchenipterids, and ageneiosids, but he did not rule out the 

 possibiUty that it may be synapomorphic at a higher level of generality. 



As evident from the brief summary presented above, there has been undue 

 emphasis on the ESA in uniting families of catfishes. The morphological diagnosis 

 of the neotropical doradoids made by Regan (1911) still stands as the first definitive 

 study to support a hypothesis that a Uneage including the Doradidae, 

 Auchenipteridae, and Ageneiosidae is monophyletic. In addition to the ESA, the 



