Taxonomic discrimination and identification of extant blue catfishes (Siluriformes: Ictaluridae: Ictalurus furcatus Group)

" Three species of the Ictalurus furcatus Group (genus Ictalurus) are recognized: I. furcatus, I. meridionalis and I. balsanus. These species are differentially diagnosed by characters of the bony skeleton, fin-ray and vertebral counts, morphometries and coloration. Ictalurus balsanus is distinctive in having a relatively short supraoccipital process, anterior nuchal plate and posterior cleithral process, weakly developed pectoral-fin spine ornamentation, and an elongated posterolateral premaxillary process. Ictalurus furcatus and I. meridionalis are closely similar species but are clearly distinguished by features of the pectoral-fin spine ornamentation, supraoccipital process shape and texture, posterior cleithral process shape, numbers of anal-fin rays and vertebrae, and related proportional measurements of anal-fin and caudal peduncle length. Apparent differences among the three species in maximum size and coloration are also noted. A limited sample of molecular sequence data from the 12S/16S mitochondrial DNA loci is consistent with morphology-based results indicating that I. meridionalis is a species distinct from I. furcatus, and that I. balsanus is the most divergent species of the three. Ictalurus furcatus and I. meridionalis exhibit inter-river basin variation in numbers of vertebrae and anal-fin rays "