FLIGHT-INITIATING QUADRUPEDAL JUMPS IN THE GIANT PTERODACTYLOID QUETZALCOATLUS: FACT OR FANTASY?

Large pterosaurs could takeoff from an elevated perch by diving into the air to initiate flight, but to take off from level ground was arduous. Our estimated mass of the giant Quetzalcoatlas from the Late Cretaceous Big Bend National Park of Texas is about 70 kg, which is close to the theoretical upper mass limit for a flying animal. Quetzalcoatlus could run bipedally downhill to pick up flying speed, a technique used by albatrosses and hang glider pilots. It has been proposed recently that Quetzalcoatlus with a new calibrated mass of 250 kg was capable of initiating flight directly from the ground using forelimbs as a catapult similar to the style of common vampire bat (~ 25 g). One issue is scaling. What is possible for a lightweight bat appears impossible for a 10,000 times heavier pterodactyloid, which, due to surface-to-volume ratios, will have approximately 0.01 times the muscle force per unit mass of the bat. Another is the height achieved by such a “pole-vault:” the maximum ballistic jump height of 2 to 3 meters would not be high enough to allow a significant downstroke, where most lift and thrust is produced. With a wingspan of 10.4 m, Quetzalcoatlus would not have been able to flap vigorously for lift generation from such a jump without smashing its delicate wings on the ground. Moreover, the animal would need about 2440 watts to fly level after jumping; the estimated maximum mechanical power available, however, even with a few seconds of maximal anaerobic muscle contraction, was approximately 1600 W, far below the flying speed that would result in crash landing. Indeed, the body mass of 250 kg itself appears to be largely overestimated, as powered flight and ground takeoff seem unlikely for an animal that heavy.