Osteological observations of the vertebral column in some species of South American Atherinids (Osteichthyes, Atheriniformes)

The shape of haemal arches of the vertebral column in several species of South American atherinids was analyzed. A large amount of variation was found, from species showing greatly expanded haemal arches connected to one another forming a cone or funnel, to others with completely unexpanded arches. The first case is hypothesized as the specialized (apomorphic) condition within the Atherinidae, on the basis of ontogenetic development.