Análise cladística de táxons atribuídos aos peixes euteleósteos basais

Abstract

Teleostei is the most diversified group among vertebrates and its oldest record dates from the Jurassic. It is currently divided into four clades, from which Euteleostei is the most derived and varied one. Despite all the studies on this group, precise diagnosis, definition, and composition are still lacking. The nine different phylogenetic hypotheses proposed in the last 30 years demonstrate the disagreement among authors. Several Cretaceous fossil fishes are assigned to basal euteleosteans due to the lack of morphological data, whereas some others possess a controversial taxonomic classification, and/or share anatomical features with basal euteleosteans. In this context, the goals of the present dissertation are to verify the monophyly of basal euteleosteans and to recover phylogenetic relationships within the taxa from Northeastern Brazil, Africa, Europe, Asia, and North America assigned to basal euteleosteans. Seven Brazilian taxa (i.e., Beurlenichthys ouricuriensis, Britoichthys marizalensis, Clupavus brasiliensis, Santanasalmo elegans, Santanichthys diasii, Scombroclupeoides scutata, and new euteleostean from the Pelotas Basin) and 14 from foregoing localities (i.e., Avitosmerus canadensis, Barcarenichthys joneti, Chanoides macropoma, Clupavus maroccanus, Gaudryella gaudryi, Humbertia operta, Kermichthys daguini, Leptolepides spratiiformis, Lusitanichthys characiformis, Nybelinoides brevis, Orthogonikleithrus leichi, Pattersonella formosa, Wenzichthys congolensis, and Tchernovichthys exspectatum) were analyzed by direct observation, as well as by means of photographs, drawings, and descriptions. After that, these taxa were submitted to a cladistic analysis using the principle of parsimony. Three living species (i.e., Elops saurus, Hoplias malabaricus, and Salmo trutta) were chosen to the outgroup. Sixtytwo characters were selected and, as a result, six equally parsimonious trees were obtained, with a length of 325 steps, consistency index (CI) of 0.2523, and retention index (RI) of 0.4309. The strict consensus tree is represented by the following topology: ((C. marocanus), (C. brasiliensis, (H. malabaricus + S. diasii))) ((G. gaudryi, (C. macropoma + L. characiformis)), (K. daguini), ((A. canadensis, (new euteleostean, (S. elegans + W. congolensis), (B. ouricuriensis + B. marizalensis)), (L. spratiiformis, (S. scutata, (N. brevis + P. formosa))), (B. joneti), (O. leichi), (H. operta + T. exspectatum), indicating that basal euteleosteans are not a monophyletic group and that the current synapomorphies are insufficient to support it.