Aerodynamic performance of the feathered dinosaur Microraptor and the evolution of feathered flight

Abstract

Understanding the aerodynamic performance of feathered, non-avialan dinosaurs is critical to reconstructing the evolution of bird flight. Here we show that the Early Cretaceous five-winged paravian Microraptor is most stable when gliding at high-lift coefficients (low lift/ drag ratios). Wind tunnel experiments and flight simulations show that sustaining a high-lift coefficient at the expense of high drag would have been the most efficient strategy for Microraptor when gliding from, and between, low elevations. Analyses also demonstrate that anatomically plausible changes in wing configuration and leg position would have made little difference to aerodynamic performance. Significant to the evolution of flight, we show that Microraptor did not require a sophisticated, 'modern' wing morphology to undertake effective glides. This is congruent with the fossil record and also with the hypothesis that symmetric 'flight' feathers first evolved in dinosaurs for non-aerodynamic functions, later being adapted to form lifting surfaces.

Mosaic evolution in an asymmetrically feathered troodontid dinosaur with transitional features

“…Furthermore, the presence of large feathers on the tail, forelimbs and hindlimbs in Jianianhualong confirms that these feathering characteristics were widely present in basal paravians54. This provides a robust troodontid basis for deepening understanding of the aerodynamic capabilities of this condition, beyond the gliding-related insights from the Jehol dromaeosaurid Microraptor 5556.…”

Aerodynamic Characteristics of a Feathered Dinosaur Measured Using Physical Models. Effects of Form on Static Stability and Control Effectiveness

“…[57] also found this posture to be stable. In contrast, Xu et al (as described on television in [34]), found the biplane to be unstable in wind tunnel tests except at high angle of attack.…”

The Origin and Diversification of Birds

“…Biomechanical study of the four-winged dromaeosaurid Microraptor suggests that it was a capable glider, although probably not capable of the kind of muscle-driven powered flight of living birds [61]. In further support of Microraptor's volant capabilities, it is the only taxon with asymmetrical hindlimb feathers (flight feathers are asymmetrical with a short and stiff leading vane and are optimized to withstand the force of the airstream), and the only non-avian with an elongated coracoid, a feature of all early birds in which a sternum is present (Jeholornis, Confuciusornis, and ornithothoracines) [62].…”