Azhdarchidae

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 Cretaceous as well (late Berriasian age, about 140 million years ago). Azhdarchids included some of the largest known flying animals of all time, but smaller cat-size members have also been found. Originally considered a sub-family of Pteranodontidae, Nesov (1984) 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. By the time of the end-Cretaceous mass extinction, most pterosaur families except for the Azhdarchidae disappear from the fossil record, but recent studies indicate a wealth of pterosaurian fauna, including pteranodontids, nyctosaurids, tapejarids and several indeterminate forms. In several analyses, some taxa such as ''Navajodactylus'', ''Bakonydraco'' and '' Montanazhdarcho'' were moved from Azhdarchidae to other clades.

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.

It had been suggested azhdarchids were skimmers, 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. 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. In another departure from typical azhdarchid lifestyles, the jaw of '' Alanqa'' may possibly be an adaptation to crushing shellfish and other hard foodstuffs.

Azhdarchids are generally medium- to large-sized pterosaurs, with the largest achieving wingspans of , but several small-sized species have recently been discovered. 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 , although similarities to the contemporary azhdarchid ''Hatzegopteryx'' have also been noted.

Systematics

Azhdarchids were originally classified as close relatives of '' Pteranodon'' due to their long, toothless beaks. Others have suggested they were more closely related to the toothy ctenochasmatids (which include filter-feeders like '' Ctenochasma'' and '' Pterodaustro''). Currently it is widely agreed that azhdarchids were closely related to pterosaurs such as ''Tupuxuara'' and '' Tapejara''.

Taxonomy

Classification after Unwin 2006, except where noted.

* Family Azhdarchidae
**'' Aerotitan''
** '' Alanqa''
** '' Aralazhdarcho''
** '' Arambourgiania''
**'' Azhdarcho''
**'' Cretornis''
**'' Eurazhdarcho''
**''Hatzegopteryx''
**''Mistralazhdarcho''
**'' Montanazhdarcho''?
**'' Palaeocursornis''
**'' Phosphatodraco''
**''Quetzalcoatlus''
**''Volgadraco''
**''Zhejiangopterus''
** Possible valid azhdarchid genera
*** '' Argentinadraco''? (azhdarchoid, tentatively classified as an azhdarchid)
***'' Bennettazhia''
***'' Bogolubovia''
***''Navajodactylus''?

Phylogeny

The most complete cladogram of azhdarchids is presented by Andres (2021):

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

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

In this analysis, ''Alanqa'' is interpreted as a non-azhdarchid azhdarchoid closely related to '' Keresdrakon''.

References

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{{Taxonbar, from=Q134363

Berriasian first appearances
Maastrichtian extinctions
Prehistoric reptile families