Avian evolution, Gondwana biogeography and the Cretaceous–Tertiary mass extinction event

Joel Cracraft

Abstract

The fossil record has been used to support the origin and radiation of modern birds (Neornithes) in Laurasia after the Cretaceous–Tertiary mass extinction event, whereas molecular clocks have suggested a Cretaceous origin for most avian orders. These alternative views of neornithine evolution are examined using an independent set of evidence, namely phylogenetic relationships and historical biogeography. Phylogenetic relationships of basal lineages of neornithines, including ratite birds and their allies (Palaeognathae), galliforms and anseriforms (Galloanserae), as well as lineages of the more advanced Neoaves (Gruiformes, Caprimulgiformes, Passeriformes and others) demonstrate pervasive trans–Antarctic distribution patterns. The temporal history of the neornithines can be inferred from fossil taxa and the ages of vicariance events, and along with their biogeographical patterns, leads to the conclusion that neornithines arose in Gondwanaprior to the Cretaceous–Tertiary extinction event.