Alternative Traditional & Phylogenetic classifications of major vertebrate groups

The traditional classification of Vertebrata recognizes seven extant taxonomic Classes, as indicated by the grouping at the top. One phylogenetic classification recognizes 13 nested clades, defined by synapomorphies at each of the numbered nodes. Among the traditional Classes, only Chondrichthyes, Aves, & Mammalia are clades; the several orders of Amphibia may or may not be a clade.