A new study, published in the journal ZooKeys, paints a startling picture about the distribution and diversity of pterosaurs of the Azhdarchidae family in the Late Cretaceous period.

The Azhdarchidan pterosaurs get their name from the Persian word Aždarha which means dragon. This group included some of the largest known pterosaurs with wingspans as large as 40 feet. The toothless animals long outlived their relatives, the toothy pterodactyloids, dominating the skies worldwide until about 60 million years ago.

“This shift in dominance from toothed to toothless pterodactyloids apparently reflects some fundamental changes in Cretaceous ecosystems, which we still poorly understand,” said Dr Alexander Averianov, the author of the study from the Zoological Institute of the Russian Academy of Sciences, in a statement.

Azhdarchidae are notoriously hard to study. Their light bones left few fossils unless it was in sedimentary deposits known as Konservat-Lagerstätten. Lagerstätten deposits are characterized by low oxygen environments with few bacteria. These environments allowed for remarkable preservation of bones and even soft tissues. Unfortunately such deposits are rare for the Late Cretaceous period, the most important for studying Azhdarchidae.

“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 undescribed for forty years.” said Dr Averianov.

Despite the rarity of fossils, enough have been found in enough areas to demonstrate that they played an important ecological role in the Cretaceous period. The researchers believe that the ‘dragons’ inhabited a wide variety of ecosystems but were most common near large bodies of water.

The article “Review of taxonomy, geographic distribution, and paleoenvironments of Azhdarchidae (Pterosauria)” can be found on the Pensoft website.