Azhdarchoidea

Azhdarchoidea is generally considered as one of three major clades of pterodactyloids. The other two major groups are Archaeopterodactyloidea and Pteranodontoidea. In some older classification schemes, azhdarchoids were considered to be closely related to ctenochasmatoids like Pterodactylus and Ctenochasma. However, most researchers no longer consider this arrangement to be very likely. Instead, azhdarchoids are grouped as close relatives of pteranodontoids under the clade Ornithocheiroidea, which would comprise the bulk of pterodactyloid diversity.

A simplified cladogram illustrating the relationships between azhdarchoids and other pterosaurs based on the analysis of Brian Andres, James Clark, and Xu Xing in 2014 is shown below.^[5]

Azhdarchoidea is generally believed to be composed of several principal families: Azhdarchidae, Chaoyangopteridae, Tapejaridae, Thalassodromidae, and potentially Dsungaripteridae, although Thalassodromidae of these is considered to be a lineage tapejarids by some researchers. However, the interrelationships of these groups is not confidently understood. The azhdarchids and chaoyangopterids are generally considered to be one another's closest relatives, but the affinities of tapejarids, thalassodromids, and dsungaripterids are controversial.^[6] Some researchers also consider an additional grouping, Alanqidae, composed of taxa formerly considered azhdarchids.^[7]

There are 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 chaoyangopterids (therein called "chaoyangopterines").^[8] 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.^[9][10]

Life reconstructions of Hatzegopteryx (top) and Arambourgiania (bottom), giant members of the family Azhdarchidae

Generally speaking, in the modern scientific literature, there are two major competing hypotheses regarding the classification of azhdarchoids. The first of these is based on the work of Brian Andres and colleagues, who have published multiple papers on the taxa Kryptodrakon, Elanodactylus, and Quetzalcoatlus among others, in which they examined the phylogenetic relationships of these groups.^[5][11] Andres and colleagues have generally suggested that Dsungaripteridae and Thalassodromidae are closely related and that they form a clade (Dsungaripteromorpha) which is more closely related to Azhdarchidae than Tapejaridae.^[5] This result has been corroborated by some other authors.^[12] A simplified version of Andres and colleagues' phylogeny is shown below.^[5]

La segunda hipótesis sobre las relaciones de los azhdárquidos es que Dsungaripteridae es el taxón hermano de Azhdarchoidea dentro del clado más grande Tapejaroidea. Esta hipótesis ha sido publicada por R. Pêgas y colegas en sus extensos estudios de pterosaurios como Sinopterus , Thalassodromeus y Aerotitan . ^{[ 7 ] [ 13 ] [ 14 ] [ 15 ]} Esta hipótesis también ha recibido apoyo de otros autores. ^{[ 16 ] [ 17 ]} Una versión simplificada de su filogenia se muestra a continuación. ^{[ 7 ]}

En 2025, Henry N. Thomas y Skye N. McDavid realizaron una revisión exhaustiva de la filogenia de los pterosaurios, centrándose en Azhdarchomorpha. Sus resultados coinciden con un análisis previo de Pêgas et al. (2024) ^{[ 15 ]} , que encontró que Tapejaroidea es monofilético y contiene a Dsungaripteromorpha y Azhdarchoidea, y que Tapejaromorpha y Azhdarchomorpha son taxones hermanos dentro de Azhdarchoidea ^{[ 18 ]} . A continuación se muestra una versión simplificada de sus resultados.