A timeline for early avian evolution. Maximum clade credibility (MCC) chronogram inferred using the non-autocorrelated model of rate evolution in BEAST while allowing topology to vary (T
Flexible). Time is given in millions of years before present. The vertical dashed line indicates the K-Pg boundary. Error bars (blue and green) represent 95% posterior credibility intervals and are only given for nodes that were present on more than 50% of the posterior sampled trees. An unambiguous ancient diversification is indicated by 37 credibility intervals restricted to the Cretaceous (green bars).