Creating testing regimes for terrestrial origins of the avian flight stroke (919.8)

Abstract

While the ancestry of birds has been firmly established within maniraptoran theropod dinosaurs, the exact timing of the origins of the flight stroke remains elusive. Debate rages as to the drivers of this critical step in the evolution of powered flight, but little biomechanical modeling has been done to test the various hypothesis proposed. Here we seek to test three proposed pathways for a terrestrial origin of flight: flap running, Wing Assisted incline Running (W.A.I.R.) and burst leaping, to examine where, if at all, on the non‐avian to avian theropod tree the aerodynamic forces required by each are possible. Based on figures generated for in‐vivo experimental data from the literature we find that W.A.I.R. is restricted, conservatively, to the sister clade to birds while flap running is biomechanically unlikely. These results will help to shape future discussion on the ecology and drivers of the origin of flight by placing theses behavioral possibilities in their evolutionary context.