Hemigrammopetersius barnardi (Teleostei: Characiformes: Alestidae): a study of skeletal ontogeny and identification of homology for phylogenetic analysis

Abstract

Members of Alestidae, a family of characiforms found in sub–Saharan Africa, have a wide range ofadult body sizes. Because of this range of adult size, phylogenetic characters for the group may be difficult to distinguish from ontogenetic features, resulting in groups being united based on body size rather than evolutionary relatedness. Although previous studies have presented the morphology and osteology of some small and miniature taxa, these were pre–cladistic and did not attempt to distinguish between phylogenetic and ontogenetic features. Here we provide a study on the external morphology and osteology of a small alestid, Hemigrammopetersius barnardi which has reductions and losses of osteological features. We compared this species to juveniles of Alestes dentex, an alestid that attains much larger adult size, to identify characters in H. barnardi that potentially result from a decrease in body size rather than shared ancestry. We found that the loss of particular bones of the circumorbital series and postcranium, as well as a reduction of the sensory canal system, are likely the result of small body size, and therefore are not useful in establishing phylogenetic relationships among alestids.