Azhdarchidae

Azhdarchids Temporal range: Ma PreꞒ Ꞓ O S D C P T J K Pg N Possible Early Cretaceous record[1]
Reconstructed skeleton of Quetzalcoatlus northropi
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Order:	†Pterosauria
Suborder:	†Pterodactyloidea
Clade:	† Azhdarchiformes
Family:	†Azhdarchidae Nesov, 1984
Type species
† Azhdarcho lancicollis Nesov, 1984
Genera
†Alanqa? †Argentinadraco? †Bogolubovia? †Montanazhdarcho? †Navajodactylus? †Palaeocursornis †Tethydraco? †Volgadraco? †Azhdarchinae †Aerotitan? †Albadraco? †Azhdarcho †Mistralazhdarcho? †Quetzalcoatlinae †Aralazhdarcho? †Arambourgiania †Cryodrakon †Eurazhdarcho? †Hatzegopteryx †Phosphatodraco? †Quetzalcoatlus †Thanatosdrakon †Wellnhopterus †Zhejiangopterus?
Synonyms
"Titanopterygiidae" Padian, 1984 (preoccupied)

Azhdarchidae (from the Persian word azhdar, اژدر, 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 Cretaceous as well (late Berriasian age, about 140 million years ago).^[1] Azhdarchids are mainly known for including some of the largest flying animals discovered, but smaller cat-size members have also been found.^[2] Originally considered a sub-family of Pteranodontidae, Nesov (1984)^[3] named the Azhdarchinae to include the pterosaurs Azhdarcho, Quetzalcoatlus, and Titanopteryx (now known as Arambourgiania). They were among the last known surviving members of the pterosaurs, and were a rather successful group with a worldwide distribution. Previously it was thought that by the end of the Cretaceous, most pterosaur families except for the Azhdarchidae disappeared from the fossil record,^[4] but recent studies indicate a wealth of pterosaurian fauna, including pteranodontids, nyctosaurids, tapejarids and several indeterminate forms.^[5] In several analyses, some taxa such as Navajodactylus, Bakonydraco and Montanazhdarcho were moved from Azhdarchidae to other clades.^[6][7][8]

Description

Azhdarchids are characterized by their long legs and extremely long necks, made up of elongated neck vertebrae which are round in cross section. Most species of azhdarchids are still known mainly from their distinctive neck bones and not much else. The few azhdarchids that are known from reasonably good skeletons include Zhejiangopterus and Quetzalcoatlus. Azhdarchids are also distinguished by their relatively large heads and long, spear-like jaws. There are two major types of azhdarchid morphologies: the "blunt-beaked" forms with shorter and deeper bills and the "slender-beaked" forms with longer and thinner jaws.^[9]

It had been suggested azhdarchids were skimmers,^[3][10] but further research has cast doubt on this idea, demonstrating that azhdarchids lacked the necessary adaptations for a skim-feeding lifestyle, and that they may have led a more terrestrial existence similar to modern storks and ground hornbills.^{[11][12][13][14][15]} Most large azhdarchids probably fed on small prey, including hatchling and small dinosaurs; in an unusual modification of the azhdarchid bodyplan, the robust Hatzegopteryx may have tackled larger prey as the apex predator in its ecosystem.^[16] In another departure from typical azhdarchid lifestyles, the jaw of Alanqa may possibly be an adaptation to crushing shellfish and other hard foodstuffs.^[17]

Azhdarchids are generally medium- to large-sized pterosaurs, with the largest achieving wingspans of 10–12 metres (33–39 ft),^[18] but several small-sized species have recently been discovered.^[19][20] Another azhdarchid that is currently unnamed, recently discovered in Transylvania, may be the largest representative of the family thus far discovered. This unnamed specimen (nicknamed "Dracula" by paleontologists), currently on display in the Altmühltal Dinosaur Museum in Bavaria is estimated to have a wingspan of 12–20 m (39–66 ft), although similarities to the contemporary azhdarchid Hatzegopteryx have also been noted.^[21]

Systematics

Azhdarchids were originally classified as close relatives of

Classification after Unwin 2006, except where noted.[22]

• Family Azhdarchidae
  • Aerotitan
  • Alanqa^[23]
  • Aralazhdarcho^[24]
  • Arambourgiania
  • Azhdarcho
  • Cretornis^[25]
  • Eurazhdarcho^[26]
  • Hatzegopteryx
  • Mistralazhdarcho^[27]
  • Montanazhdarcho?^[6]
  • Palaeocursornis
  • Phosphatodraco
  • Quetzalcoatlus
  • Volgadraco^[28]
  • Zhejiangopterus
  • Possible valid azhdarchid genera
    • Argentinadraco? (azhdarchoid, tentatively classified as an azhdarchid)^[29]
    • Bennettazhia
    • Bogolubovia
    • Navajodactylus?

Phylogeny

The most complete cladogram of azhdarchids is presented by Andres (2021):^[30]

In the analysis Cretornis and Volgadraco were recovered as pteranodontians, Alanqa was recovered as a thalassodromine, and Montanazhdarcho was recovered just outside Azhdarchidae.^[30]

An alternate phylogeny of Azhdarchidae was presented by Ortiz David et al. (2022) in their description of Thanatosdrakon:^[31]

In this analysis, Alanqa is interpreted as a non-azhdarchid azhdarchoid closely related to Keresdrakon.^[31]

References