THE ORIGIN AND EARLY DIVERSIFICATION OF TETRAPODS

A series of new fossil discoveries, coupled with cladistic analysis of old and new data, is beginning to resolve the origin of tetrapods into a documented sequence of character acquisition. Devonian tetrapods were more fish-like than believed previously, whereas Lower Carboniferous tetrapod faunas contain early representatives of the amphibian and amniote lineages. These very different assemblages are separated by a 20-million-year 'Tournaisian gap' which has yielded very few tetrapod fossils.