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Azhdarchoids; Temporal range: ; Early - Late Cretaceous, 143–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N Possible Late Jurassic record
	Reconstructed skeleton of Quetzalcoatlus northropi
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Order:	†Pterosauria
Suborder:	†Pterodactyloidea
Clade:	†Ornithocheiroidea
Clade:	†Azhdarchoidea; Nesov, 1984
Subgroups
	†Inabtanin; †Ornithostoma; †Tapejaromorpha; †Neoazhdarchia †Dsungaripteromorpha? †Microtuban?; †Dsungaripteridae; †Thalassodromidae?; ; †Azhdarchomorpha †Keresdrakon?; †Neopterodactyloidea †Eoazhdarcho; †Chaoyangopteridae; †Azhdarchiformes †Radiodactylus; †Montanazhdarcho; †Azhdarchidae; †Alanqidae? †Alanqa; †Argentinadraco?; †Leptostomia?; †Montanazhdarcho?; †Xericeps?; ; ; ; ; ;

Azhdarchoidea (or azhdarchoids) is a group of pterosaurs within the suborder Pterodactyloidea, more specifically within the group Ornithocheiroidea. Pterosaurs belonging to this group lived throughout the Early and Late Cretaceous periods, with one tentative member, Tendaguripterus, that lived in the Late Jurassic period. The largest azhdarchoids include members of the family Azhdarchidae, examples of these are Quetzalcoatlus, Hatzegopteryx, and Arambourgiania. Other notable pterosaur families belonging to the Azhdarchoidea are the Tapejaridae, the Thalassodromidae, and the Chaoyangopteridae. This group contains some of the most advanced members of the pterosaur order.

The interrelationships of the Azhdarchoidea have varied throughout history, a few having recovered it as closely related to the Ctenochasmatoidea, though this placement is largely obsolete nowadays. Most studies have found it to be either as the sister taxon of the family Dsungaripteridae within the clade Tapejaroidea, itself within the larger Ornithocheiroidea, or as the sister taxon of the clade Pteranodontoidea. Within Azhdarchoidea, two big groups have largely been consistent, the first one consisting of pterosaurs more closely related to tapejarids, such as Tapejara, while the second one comprising pterosaurs more closely related to azhdarchids, such as Quetzalcoatlus. Over the years, new clades within Azhdarchoidea have been named following the division mentioned before. One is Tapejaromorpha, which would include the pterosaurs bearing more tapejarid-like features, while the other is Azhdarchomorpha, consisting of pterosaurs with more azhdarchid-like features.

Classification

Reconstructed skeletons of Quetzalcoatlus (above) and Tapejara (below), the two pterosaurs used in the definition of Azhdarchoidea by David Unwin

Azhdarchoidea was given a phylogenetic definition by paleontologist David Unwin in 2003. Unwin defined the group as the most recent common ancestor of Quetzalcoatlus and Tapejara, and all its descendants.^[2]

Early on, there have been several competing views of azhdarchoid relationships. An early study presented by paleontologist Felipe Pinheiro and colleagues in 2011 considered the tapejarids to be a monophyletic clade including the thalassodromines and the chaoyangopterines.^[3] Other earlier studies, such as that of paleontologists Darren Naish & David Martill in 2006, and that of Lü Junchang and colleagues in 2008, considered the traditional "tapejarids" to be a paraphyletic grade of primitive azhdarchoids, with true tapejarids more basal, and the thalassodromines (alternatively called thalassodromids) and chaoyangopterids being successively more closely related to azhdarchids.^[4]^[5] All azhdarchoids which are part of a clade formed by Quetzalcoatlus and Tupuxuara are included in the group Neoazhdarchia ("new azhdarchids") as defined by Unwin in 2003.^[2]

In 1996, paleontologist Alexander Kellner created a different clade called Tapejaroidea, which he defined as the most recent common ancestor and all descendants of Tapejara, Quetzalcoatlus, and Dsungaripterus. Kellner created this clade to include both Azhdarchoidea and the family Dsungaripteridae, but as separate groups.^[6]^[7] A lot of recent studies have followed this concept.^[8]^[9]^[10]^[11]

Regarding the phylogeny of the Azhdarchoidea, there have been many different and conflicting studies, its intra-relationships have been especially convoluted. A few early studies have recovered it as closely related to the clade Ctenochasmatoidea.^[2]^[12] However, this assignment has not been largely followed. All recent analyses have found Azhdarchoidea within the larger group Ornithocheiroidea, with opposing studies agreeing upon this placement.^[13]^[14]^[9]^[11]^[10] However, the clades included within Azhdarchoidea are very disputed. On one side, there are studies that have adopted Unwin's concept of Neoazhdarchia. Azhdarchoidea would be divided into the clades Neoazhdarchia and Tapejaromorpha, the latter consisting of azhdarchoids more closely related to Tapejara. Neoazhdarchia would be further divided into two subgroups, the Dsungaripteromorpha and the Neopterodactyloidea, the former comprising the families Dsungaripteridae and Thalassodromidae, while the latter included the families Chaoyangopteridae and the Azhdarchidae.^[13]^[14]

Life restorations of Thalassodromeus (above) and Tupuxuara (below). Both belong to the Thalassodromidae, which, depending on the phylogeny, is either closely related to the Tapejaridae or the Dsungaripteridae

On another side, there are studies adopting Kellner's model of Azhdarchoidea. Dsungaripteridae would be found outside it as a sister taxon, both forming the clade Tapejaroidea, itself nested within the Ornithocheiroidea. Within Azhdarchoidea, Tapejaromorpha would bear a different structure. The families Thalassodromidae and Tapejaridae would be closely related within Tapejaromorpha, effectively rejecting the concept of Dsungaripteromorpha. A clade named Azhdarchomorpha would later be defined by paleontologist Rodrigo Pêgas and colleagues in 2021 as the most inclusive clade containing Azhdarcho but not Tapejara or Thalassodromeus. Azhdarchomorpha encompasses two different clades, the family Chaoyangopteridae and the Azhdarchiformes, the latter consisting of azhdarchoids bearing more azhdarchid-like characteristics. Azhdarchiformes would be further divided into the families Alanqidae, which includes species more closely related to Alanqa, and Azhdarchidae.^[15]^[16]^[17]^[18]

Two cladograms are shown below. The first one is by paleontologist Brian Andres in 2021, which finds the clades Neoazhdarchia and Tapejaridae as sister taxa. Neoazhdarchia is divided into the Dsungaripteromorpha, itself comprising Microtuban, Dsungaripteridae and Thalassodromidae, and the Neopterodactyloidea, itself comprising Chaoyangopteridae and Azhdarchiformes. Azhdarchoidea is the sister taxon of Pteranodontoidea in this study.^[19] The second cladogram is by Pêgas in 2024, which divides Azhdarchoidea into the clades Tapejaromorpha, which comprises Thalassodromidae and Tapejariformes (the latter containing Tapejaridae), and Azhdarchomorpha, which consists of Keresdrakon, Chaoyangopteridae, and Azhdarchiformes. Azhdarchiformes is further divided into Alanqidae and Azhdarchidae. Azhdarchoidea and Dsungaripteridae are sister taxa in this analysis, both forming the clade Tapejaroidea.^[17]