Toothless pterosaurs, flying dinosaurs, once held dominance over the skies during the Cretaceous Period, the last age of the dinosaurs.

Azhdarchidan pterosaurs sported wings 30 to 40 feet in length, giving them the distinction of being one of the largest animals to ever take to the skies. The giant flying creatures learned to live in many parts of the world, just before the end of the age of dinosaurs.

The Cretaceous Period started 145 million years ago, and ended in a global disaster, as an asteroid the size of Mount Everest struck the Earth 65 million years ago. The earliest flying dinosaurs possessed teeth - it was not until later toothless varieties of the transitional creatures between true dinosaurs and birds became dominant.

Azhdarchidans lived near waterways, including rivers and lakes.

Paleontologists from the Zoological Institute of the Russian Academy of Sciences analyzed the remains of many Azhdarchidae fossils, showing how the family of flying dinosaurs maintained air superiority millions of years ago.

"This shift in dominance from toothed to toothless pterodactyloids apparently reflects some fundamental changes in Cretaceous ecosystems, which we still poorly understand," Alexander Averianov, from the Russian Academy of Sciences, said.

Toward the end of the age of dinosaurs, toothless varieties of pterosaurs took over the skies from their toothed cousins.

The species is named after the Persian word for dragon, "Aždarha." Although they lived in many parts of the world, few fossils of the species have been found, making study of the animals a challenge. The bones of the creatures were extremely fragile, meaning they were not often preserved after death. Certain sedimentary deposits, known as Konservat-Lagerstätten layers, were the only method of fossilization for the creatures. However, these formations rarely formed during the late Cretaceous, when the toothless flying dinosaur lived.

"Azhdarchidae currently represent a real nightmare for paleontologists: most taxa are known from few fragmentary bones, which often do not overlap between named taxa, the few articulated skeletons are poorly preserved, and some of the best available material has remained un-described for forty years," Averianov told the press.

The Night Fury, a form of flying reptile from How to Train Your Dragon, was said to be a cross between "lightning and death itself." Night Furies are said to be the smartest, fastest and rarest of all dragons. The only known member of that fictional species was an individual named Toothless.

Investigation of the dominance of toothless pterosaurs at the end of the Cretaceous Period was detailed in the journal ZooKeys.