lifestyle, instead suggesting that Quetzalcoatlus scavenged like the marabou stork (which will scavenge, but is more of a terrestrial predator of small animals), but then on the carcasses of titanosaur sauropods such as Alamosaurus. Lawson had found the remains of the giant pterosaur while searching for the bones of this dinosaur, which formed an important part of its ecosystem. In 1996, Lehman and Langston rejected the scavenging hypothesis, pointing out that the lower jaw bent so strongly downwards that even when it closed completely a gap of over remained between it and the upper jaw, very different from the hooked beaks of specialized scavenging birds. They suggested that with its long neck vertebrae and long toothless jaws Quetzalcoatlus fed like modern-day skimmers, catching fish during flight while cleaving the waves with its beak. While this skim-feeding view became widely accepted, it was not subjected to scientific research until 2007 when a study showed that for such large pterosaurs it was not a viable method because the energy costs would be too high due to excessive drag. In 2008 pterosaur workers Mark Witton and Darren Naish published an examination of possible feeding habits and ecology of azhdarchids. Witton and Naish noted that most azhdarchid remains are found in inland deposits far from seas or other large bodies of water required for skimming. Additionally, the beak, jaw, and neck anatomy are unlike those of any known skimming animal. Rather, they concluded that azhdarchids were more likely terrestrial stalkers, similar to modern storks, and probably hunted small vertebrates on land or in small streams. Though Quetzalcoatlus, like other pterosaurs, was a quadruped when on the ground, Quetzalcoatlus and other azhdarchids have fore and hind limb proportions more similar to modern running ungulate mammals than to their smaller cousins, implying that they were uniquely suited to a terrestrial lifestyle. Flight The nature of flight in Quetzalcoatlus and other giant azhdarchids was poorly understood until serious biomechanical studies were conducted in the 21st century. One early (1984) experiment by Paul MacCready used practical aerodynamics to test the flight of Quetzalcoatlus. MacCready constructed a model flying machine or ornithopter with a simple computer functioning as an autopilot. The model successfully flew with a combination of soaring and wing flapping; the model was based on a then-current weight estimate of around , far lower than more modern estimates of over . The method of flight in these