The origin of vertebrates represents one of the most fundamental events in animal evolution. This occurs not only because this episode represents the establishment of our own evolutionary lineage, but because it coincides with one a singularly dramatic episode in genetic and developmental evolution. Hence, it is the focus of interest of researchers from a great variety of disciplines, including palaeontologists, comparative anatomists, embryologists, as well as developmental geneticists and molecular phylogeneticists.

Figure: interrelationships of fossil and living early vertebrates and their immediate invertebrate kin. The fossil taxa demonstrate that the transition from jawless to jawed vertebrates was a protracted episode of gradual character acquisition, not a dramatic leap driven my genome duplication. From Donoghue and Purnell (2005).

Our aim is to provide an integrated framework for understanding the sequence of events in which the body plan of vertebrates and jawed vertebrates was established. This is achieved through comparative analysis of living and fossil vertebrates, and their immediate relatives among the invertebrates. This is used as a basis for the development of schemes of their evolutionary relationships, and the resulting patterns of character evolution, used subsequently to constrain hypotheses of developmental evolution.

In particular, we have focussed on the evolution of development of the vertebrate skeleton, uncovering the sequence and nature of appearance of each of the component embryological systems that comprise the skeleton. This has revealed that what is taken to be a single coherent 'vertebrate skeleton' is actually an evolutionary and embryological chimaera that is characteristic of the group of living jawed vertebrates alone.