Flight, symmetry and barb angle evolution in the feathers of birds and other dinosaurs.

There has been much discussion over whether basal birds (e.g. and exhibited active flight.

Phylogenetics and ecomorphology of emarginate primary feathers.

Wing tip slots are a distinct morphological trait broadly expressed across the avian clade, but are generally perceived to be unique to soaring raptors. These slots are the result of emarginations on the distal leading and trailing edges of primary feathers, and allow the feathers to behave as individual airfoils. Research suggests these emarginate feathers are an adaptation to increase glide efficiency by mitigating induced drag in a manner similar to aircraft winglets.