Early vertebrates and their extant relatives

Abstract The phylogenetic and systematic framework of extant craniates given in the preceding chapter is based on characteristics of all kinds, although morphological ones are still by far the most reliable, in the absence of the methodological stability of molecular systematics. The source of information represented by these neontological characteristics is not unlimited but it is far from thoroughly explored. Although great weight is given now to molecular sequence data, the anatomy of many of the best-known extant craniates still reveals features that had gone unnoticed by zoologists for two centuries. Our interpretation of the phylogeny of extant craniates can be expected to become more stable, and better and better corroborated, as knowledge of their structure grows.