The Flight Performance of the Crested Pterodactyloid Tapejara from the Early Cretaceous of Brazil

Recent discovery of soft cranial crest in some pterodactyloids has generated a great deal of speculation about its possible aerodynamic functions in life. In Tapejara wellnhoferi , an early Cretaceous pterodactyloid from Brazil, an enormous membranous cranial sail stretched upward and backward considerably from the sagittal bony crest like a thin stiff circular blade making the skull extremely tall and long. The multitasking cranial sail probably functioned in life for sexual display, species recognition, mass balancing of long jaws, aerodynamic stability and control, vertical stabilizer, rudder, and thermoregulation. The compliant membrane wings of Tapejara are long, narrow, and sweepback with high aspect ratio, reinforced by actinofibrils for structural integrity. It is likely that both cranial sail and wing membrane were richly supplied with blood vessels and nerve endings and acted as sensory organs to relay aerodynamic information to the vestibular apparatus of the inner ear, a tiny gyroscope, for flight control and stability. A computer simulation model of the flight performance of Tapejara suggests that it could takeoff under its own muscle power with a running speed of 3 m/s and a liftoff distance of 2 m. Tapejara had a significant margin of power above that needed for cruising flight, which could have provided good maneuverability. Its minimum steady turn radius under maximum aerobic power is estimated to be about 7 m at airspeed of 36 km/hr. The area of large head crest appears to be about 40 percent of wing area, but its additional friction drag does not greatly impede estimated flight performance except at high speeds. However the precise role of the crest in maneuvering flight remains uncertain.