They may have been the largest flying creatures that the Earth has known, but many pterosaurs preferred to walk, according to new research.

The biggest family of the prehistoric winged reptiles probably fed like modern storks and ground hornbills, stalking prey on foot before grabbing it with their monstrous jaws, British scientists have found.

The azhdarchids, a type of pterosaur that lived in the age of the dinosaurs and had a wingspan that could exceed 10m (33ft), have long been assumed to have been aquatic predators that grabbed fish in a fashion similar to gulls and pelicans.

A new analysis of their anatomy, distribution and footprints, however, has now suggested that they are more likely to have been ground-based predators. Even fox-sized small dinosaurs would have been suitable prey, so large were their jaws.

Azhdarchids, which take their name from the Uzbek word for dragon, lived between 230 million and 65 million years ago. The biggest forms, such as Quetzalcoatlus northropi, stood as tall as a giraffe.

Mark Witton and Darren Naish, of the University of Portsmouth, have now compared azhdarchid fossils with modern birds, revealing striking differences from those that grab prey while in flight or probe the mud for food. “Azhdarchids first became reasonably well known in the 1970s, but how they lived has been the subject of much debate,” Dr Naish said.

“Originally described as vulture-like scavengers, they were later suggested to be mud-probers — sticking their long bills into the ground in search of prey — and later still suggested to make a living by flying over the water's surface, grabbing fish.

“We argue that azhdarchids were specialised terrestrial stalkers. All the details of their anatomy, and the environment their fossils are found in, show that they made their living by walking around, reaching down to grab and pick up animals and other prey.”

Other features of the animals' anatomy, such as their stiff necks and small feet, also point towards a terrestrial lifestyle. The findings are published in the journal Public Library of Science One.

Dr Naish said: “We also worked out the range of motion possible in the azhdarchid neck. This bizarrely stiff neck has previously been a problem for other ideas about azhdarchid lifestyle, but it fits with our model, as all a terrestrial stalker needs to do is raise and lower its bill tip to the ground.”

Mr Witton said: “The small feet of azhdarchids were no good for wading around lake margins or swimming, should they land on water, but are excellent for strutting around on land.

“As for what azhdarchids would eat, they would have snapped up bite-size animals or even bits of fruit. But if your skull is over two metres in length then bite-size includes everything up to a dinosaur the size of a fox.”

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