ABSTRACT
The phylogenetic position of the Gonorynchiformes is linked to a number of more general phylogenetic problems. From the beginning of phylogenetic systematics in ichthyology, the monophyly of ostariophysans was part of the discussion of the gonorynchiform interrelationships and must be considered first, then the position of the Ostariophysi among teleosts. Results from molecular, as well as morphological, systematics of teleosteans of the last fifteen years showed that the sister group of ostariophysans was the Clupeomorpha. It then became necessary to redefine euteleosts, which, in turn, required an assessment of the position of esocoids among teleosts. Finally, some discussions among ichthyologists about the monophyly of otophysans involved hypotheses about the position of gonorynchiformes and therefore led to a discussion of the phylogeny within ostariophysans. All these problems are reviewed by considering that a molecular phylogeny obtained through a single data set is not enough to falsify a morphological one. A clade is considered reliable when it has been corroborated through several independent sources of data. In other words, morphological synapomorphies are falsified and have to be revised only when they have been contradicted by several independent molecular phylogenies. Gonorynchiformes is the sister group of otophysans, forming the monophyletic Ostariophysi. Ostariophysans and clupeomorphs are sister groups and form the Otocephala. The sister group of the Otocephala is the Euteleostei, among which esocoids are sister group of salmonoids. Finally, something new recently appeared in that general picture. The Alepocephaloidea, which is generally considered the sister group of the Argentinoidea, could be either a member of the Otocephala or the closest sister group of it. However, those two possibilities cannot be considered reliable at present and must be taken as working hypotheses. More independent data are needed to test them.
