Abstract

The pectoral fins in fishes are important anatomical structures for the locomotive dynamics and the identification of taxonomic groups. However, many taxa show wide intra- and inter-specific variability for this character, related with different evolutionary mechanisms and explained by successive accumulated changes. We studied the shape and form of the pectoral fin in different species of the family Characiidae, with the premise that the changes that occur in these organisms are parsimonious. First, we evaluated the shape of the pectoral fin using the geometric morphometrics landmarks. Second, we locate the samples in a space based in the centroid size and the mean size, obtaining a linear regression. The shifting morphology can be showed when we build morfoclines by applying a mathematical transformation in the relative position of the landmarks, constrained by the regression coefficient. These results are compared with the phylogeny described for the taxon to determine the relationship between congruence between species and the morphological changes observed.

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