''Cryodrakon'' ("cold dragon") is a genus of

azhdarchid Azhdarchidae (from the Persian word , , a dragon-like creature in Persian mythology) is a family of pterosaurs known primarily from the Late Cretaceous Period, though an isolated vertebra apparently from an azhdarchid is known from the Early Cre ...

pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the Order (biology), order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cre ...

that lived during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

period in what is now

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...

. It contains a single species, ''Cryodrakon boreas'', recovered from the

Dinosaur Park Formation The Dinosaur Park Formation is the uppermost member of the Belly River Group (also known as the Judith River Group), a major geologic unit in southern Alberta. It was deposited during the Campanian stage of the Late Cretaceous, between about 7 ...

Discovery and history

Significant pterosaur discoveries in western North America

Since 1972, bones of large

azhdarchids Azhdarchidae (from the Persian word , , a dragon-like creature in Persian mythology) is a family of pterosaurs known primarily from the Late Cretaceous Period, though an isolated vertebra apparently from an azhdarchid is known from the Early ...

have been reported from

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

, representing the first pterosaur finds from Canada. These were sometimes referred to a ''

Quetzalcoatlus ''Quetzalcoatlus'' is a genus of pterosaur known from the Late Cretaceous period of North America (Maastrichtian stage); its members were among the largest known flying animals of all time. ''Quetzalcoatlus'' is a member of the Azhdarchidae, ...

'' sp. Later research by Michael Habib indicated that they represented a

taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

new to science. In 2019, the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

''Cryodrakon boreas'' was named and described by David William Elliott Hone, Michael Habib and François Therrien. The generic name is derived from the Greek κρύος, ''kryos'', "icy cold", and δράκων, ''drakon'', "dragon". The specific name means "belonging to '' Boreas'', the north wind", or simply "northern". Habib had considered the name ''Cryodrakon viserion'', as a reference to the ice dragon in ''

Game of Thrones ''Game of Thrones'' is an American fantasy drama television series created by David Benioff and D. B. Weiss for HBO. It is an adaptation of ''A Song of Ice and Fire'', a series of fantasy novels by George R. R. Martin, the firs ...

''. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

, TMP 1992.83, was found in a layer of the Dinosaur Park Formation dating from the late

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

. The layer is between 76.7 and 74.3 million years old, with the excavation site being located near the lower or older boundary of this range. It consists of a partial skeleton lacking the skull. It contains a fourth neck vertebra, a rib, a humerus, a pteroid bone, a fourth metacarpal, a shinbone and a metatarsal. In 1992, the skeleton was excavated in Quarry Q207 and in 1995 reported and partially described. Its bones were not articulated but associated. It represents an immature individual. It is the only pterosaur skeleton, as opposed to single bones, ever found in Canada. It was described in more detail in 2005.Currie, P.J., and E.B. Koppelhus (eds.). 2005. ''Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed''. Indiana University Press, Bloomington, Indiana, 672 pp All the known azhdarchid material from the Dinosaur Park Formation was referred to the species. The specimens consisted of the neck vertebrae TMP 1996.12.369, TMP 1981.16.107, TMP 1980.16.1367, TMP 1989.36.254 and TMP 1993.40.11; the scapulocoracoid TMP 1981.16.182; the ulna TMP 1965.14.398; fourth metacarpals TMP 1979.14.24, TMP 1987.36.16 and TMP 2005.12.156; wing finger phalanges TMP 1972.1.1, TMP 1982.19.295 and TMP 1992.36.936; and the thighbone TMP 1988.36.92. The bones represent individuals of various biological ages, among them juveniles and a large mature exemplar. Most bones are from medium-sized animals. In 2019, only the neck vertebrae were described in detail; bones from other parts of the body had already been treated in 2005.

Description

The material indicates individuals of varying size. Specimen TMP 1996.12.369, a fifth neck vertebra with a length of only , is from a juvenile animal with an estimated wingspan of about . Most bones, among them the holotype, are similar in dimensions to those of ''

lawsoni'', implying a wingspan of about . Specimen TMP 1980.16.1367, originally mistaken as a leg bone in 1982, is a fifth neck vertebra with an estimated original length of , indicating an animal equal in size to the holotype of ''Quetzalcoatlus northropi'', the wingspan of which has been initially estimated at , but then moderated at . ''Cryodrakon'' was proportionally similar to ''Quetzalcoatlus'' and other long-necked advanced azhdarchids, though its somewhat more robust bones may indicate that it was slightly heavier. ''Cryodrakon'' is distinguished from all other known azhdarchids by two features of its neck vertebrae. The lateral pneumatic fossae or pneumatopores, a pair of small openings leading to air pockets on either side of the neural canal, were positioned near the lower edge of the

neural canal In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural fold become elevated, a ...

, while those of other azhdarchids (with the purported exception of ''

Eurazhdarcho ''Eurazhdarcho'' is a genus of azhdarchid pterosaur from the Late Cretaceous period ( Maastrichtian stage) of what is now the Transylvanian Basin of Romania. Its fossil remains dated back 69 million years ago. Discovery and naming In 2009, M ...

'') were positioned higher up. The second distinguishing feature related to its postexapophyses, large bony knobs adjacent to the protruding rear connection surface of each vertebra, the cotyle. ''Cryodrakons postexapophyses were prominent in width but short in length, clearly separated from the cotyle, and their facets were directed downwards.

Classification

''Cryodrakon'' was placed in the Azhdarchidae in 2019. No exact

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived ch ...

analysis was given clarifying the precise relationships with other azhdarchids. It would have been one of the oldest known azhdarchids of North-America. Then in 2021, Brian Andres performed a phylogenetic analysis on ''

'', including ''Cryodrakon'' in the study. It was in a trichotomy with '' Wellnhopterus brevirostris'' and ''Quetzalcoatlus northropi'', ''Q. lawsoni'', '' Hatzegopteryx thambena'', and '' Arambourgiania philadelphiae''. Below are the results of the study.

Paleobiology

''Cryodrakon'' is thought to have been capable of flight, and if it was, it would have been one of the largest flying animals known to have existed. Azhdarchid pterosaurs similar to ''Cryodrakon'' are currently thought to have fed by hunting for smaller animals while on the ground, similar to modern day

marabou storks The marabou stork (''Leptoptilos crumenifer'') is a large wading bird in the stork family Ciconiidae native to sub-Saharan Africa. It breeds in both wet and arid habitats, often near human habitation, especially landfill sites. It is someti ...

Palaeoenvironment

The Dinosaur Park Formation, where fossils of ''Cryodrakon'' have been excavated, preserves many fossils from alluvial and coastal plain environments. Both of these environments would have experienced high precipitation, warm temperatures, and high humidity, with conditions becoming more swamp-like as time progressed. There was a great diversity of herbivorous dinosaurs including both

lambeosaurine Lambeosaurinae is a group of crested hadrosaurid dinosaurs. Classification Lambeosaurines have been traditionally split into the tribes or clades Parasaurolophini (''Parasaurolophus'', '' Charonosaurus'', others (?).) and Lambeosaurini ('' ...

and

saurolophine Saurolophinae is a subfamily of hadrosaurid dinosaurs. It has since the mid-20th century generally been called the Hadrosaurinae, a group of largely non-crested hadrosaurs related to the crested sub-family Lambeosaurinae. However, the name Had ...

hadrosaurs,

centrosaurine Centrosaurinae (from the Greek, meaning "pointed lizards") is a subfamily of ceratopsid dinosaurs, a group of large quadrupedal ornithischians. Centrosaurine fossil remains are known primarily from the northern region of Laramidia (modern day ...

and

chasmosaurine Chasmosaurinae is a subfamily of ceratopsid dinosaurs. They were one of the most successful groups of herbivores of their time. Chasmosaurines appeared in the early Campanian, and became extinct, along with all other non-avian dinosaurs, during ...

ceratopsians, and

nodosaurid Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous period in what is now North America, South America, Europe, and Asia. Description Nodosaurids, like their close relatives the ankylosaurids, w ...

and

ankylosaurid Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. The oldest known Ankylosaurids date to around 122 million years ago and went extinct 66 million years ago during the Cretaceous–Pal ...

ankylosaurs, which could have been able to feed on different vegetation levels from one another. The predatory niches were occupied by small

maniraptoran Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to ''Ornithomimus velox''. It contains the major subgroups Avialae, Deinonychosauria, Oviraptoros ...

theropods Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

, medium-sized juvenile

tyrannosaurids Tyrannosauridae (or tyrannosaurids, meaning " tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to thirteen genera, including the eponymous '' Tyrannosaurus''. The exact number of ...

, and fully grown tyrannosaurids. A partial skeleton was found to have been scavenged by a

dromaeosaurid Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

, possibly ''

Saurornitholestes langstoni ''Saurornitholestes'' ("lizard-bird thief") is a genus of carnivorous dromaeosaurid theropod dinosaur from the late Cretaceous of Canada ( Alberta) and the United States ( Montana, New Mexico, Alabama, North Carolina, and South Carolin ...

''. A broken tooth was found in one of the bones, which according to the authors, meant that the thin-walled bone "must have been very tough."

References