Alternative tree topologies. T
Consensus (left) represents a conservative consensus estimate of avian familial relationships  (AICc = 421460.9166). T
Optimal (right) is our optimal topology derived from a partitioned model maximum likelihood search in RAxML (AICc = 414160.2536). Some topological constraints were implemented in this search (see additional file 1). Solid circles and numbers indicate the placement of calibration points (see Table 5 for ages). Letters denote nodes whose age estimates are provided in Table 3.