Cryodrakon

Cryodrakon is a genus of azhdarchid pterosaur that lived during the late Campanian age of the Late Cretaceous period in what is now Canada, around 76.7 and 74.3 million years ago. Starting in 1972, fossil remains of large azhdarchid pterosaurs have been reported from Alberta. Paleontologists assigned them to the genus Quetzalcoatlus, given that it was the only known azhdarchid from North America back then and because they had limited information about its actual remains, so they simply could not deduce anything different. In 1992, a partial pterosaur skeleton was uncovered in the Dinosaur Park Formation of Alberta. It was partially described in 1995 by paleontologist Philip J. Currie and colleagues, with a subsequent and more complete description in 2005. But it was not until 2019 that it received a new genus and type species, Cryodrakon boreas, named and described by paleontologists David Hone, Michael Habib, and François Therrien. The partial skeleton was made the holotype specimen of this new pterosaur. Its generic name means "cold dragon" in Ancient Greek, in reference to its Canadian origin, while its specific name refers to the Greek god of the north winds, Boreas. All azhdarchid remains from the Dinosaur Park Formation were subsequently referred to Cryodrakon.

Most of the fossil remains of Cryodrakon belong to either young or subadult individuals, from which a wingspan of about 5 m (16 ft) could be estimated. However, much larger fossils have been unearthed, including an incomplete fifth cervical (neck) vertebra that measures 40 cm (1 ft 4 in). If complete, it could have measured at least 50 cm (1 ft 8 in). Adult individuals of Cryodrakon would have had a similar size to Quetzalcoatlus northropi based on the size of its fossils. A wingspan of about 10 m (33 ft) is the most commonly estimated for Cryodrakon, which makes it one of the largest flying animals to ever exist.

In its description, Cryodrakon was assigned to family Azhdarchidae, which includes the already mentioned Quetzalcoatlus. A phylogenetic analysis was not performed due to the fragmentary nature of its remains, but the describers pointed out certain features that would exclude Cryodrakon from being in a basal (primitive) position within Azhdarchidae. Subsequent phylogenetic analyses would place it within the subfamily Quetzalcoatlinae, though in varying position depending on the study. Cryodrakon would have coexisted with many different types of dinosaurs in the Dinosaur Park Formation, as demonstrated by the abundance of dinosaur fossils found there.