Interpreting the fossil record and the origination of birds

Abstract

The fossil record is essential for understanding when lineages originate and their pace of diversification. However, numerous taphonomic biases in the fossil record can hinder interpretation, creating discord between palaeontological and phylogenetic estimates of clade origination dates. Here, I use the recently published Bayesian Brownian Bridge method to infer the age of birds using occurrence data from the Paleobiology Database. I also estimate the age of the speciose sub-clade Telluraves to compare age estimates with previous tip-dating analyses of the same group. Analyses of all birds show place the root age approximately 100 Ma, approximately 26 Myr before the oldest fossil occurrences. Increasing the time bin size from 2.5 to 5 Myr produced significantly older and less precise estimates. Divergence estimates for Telluraves were strikingly consistent with tip-dating analyses, placing origination of the group in the latest Cretaceous. Although these dates are consistent with a hypothesis of Mesozoic origination and Cenozoic diversification, significant diversification was estimated before the end-Cretaceous mass extinction suggesting analyses using pooled species counts may produce spurious results. Overall, these analyses provide further evidence to a growing consensus that several major avian lineages survived the end-Cretaceous mass extinction before diversifying into the most speciose extant tetrapod radiation.