ABSTRACT
The order Acipenseriformes is the only extant one among Chondrostea whose origin dates back as early as Jurassic. Phylogenetic ancestry and anatomical characteristics make the order especially relevant for the reconstruction of evolutionary history of vertebrates. Acipenseriformes include two families, Acipenseridae and Polyodontidae. The first one, Acipenseridae, is commonly divided into two subfamilies, Scaphyirhynchinae and Acipenserinae. Cytogenetic and molecular data gave further insights into species differentiation processes within the order, suggesting new taxonomical and phylogenetic relationships among species groups. Chromosome-banding techniques, developed in the early 1970s, greatly contributed to the knowledge of vertebrate karyotype. However, the lack of compartimentalization in fish DNA base composition greatly limited the application of such techniques. Molecular markers can be used to directly infer the ploidy level of the genome by analysing the maximum number of alleles found at a given locus in one individual.
