Arambourgiania

, who first studied the specimen. In 1943, during phosphate mining operations near the town of Ruseifa, Jordan, a railway worker found several fossil fragments associated with an incomplete fossilized cervical (neck) vertebra measuring in length. Later in the same year, these fossils were acquired by Amin Kawar, the director of a nearby phosphate mine. Kawar brought the fossils to the attention of Dr. Gerald Lankester Harding, the Director of Antiquities at the British Residence in Amman (at the time Jordan was a British protectorate) who then examined the remains. The vertebra generated some publicity — it was even shown to Abdullah I of Jordan. Subsequently, the fossils were transferred to the Hebrew University of Jerusalem where reports of their origin, anatomy, and location were filed, with copies then sent to the Jordan Phosphates Mines Company. Unfortunately, these reports have since been destroyed, though there may be existing records at the Hebrew University. The phosphates in which the fossil was found belong to the Ruseifa Formation, which dates to the Maastrichtian age (72–66 million years ago) of the Late Cretaceous period. In 1975 while studying Quetzalcoatlus, American paleontologist Douglas A. Lawson correctly concluded that the holotype was not a metacarpal but a cervical vertebra. In the 1980s, an entomologist informed Russian paleontologist Lev Nessov that the name Titanopteryx had already been given to a fly from the Simuliidae family in 1935. Therefore, in 1989, he created the new genus name Arambourgiania, honoring Arambourg, with -iania being a suffix indicating possession. However, the name "Titanopteryx" was informally kept in use in the West despite being a preoccupied name. In 1992, Lewy and colleagues described a pair of endocasts (a natural cast of the brain cavity) which had been unearthed from upper Campanian or early Maastrichtian-aged phosphates belonging to the Mishash Formation located near Mitzpe Ramon, Israel. Lewy referred these endocasts to Titanopteryx (=Arambourgiania) sp. (sp. meaning an indeterminate species) on the basis of their similarity to the endocasts of pterosaurs. However, these endocasts have no overlap with any described fossils of Arambourgiania and, according to a 2014 study, most likely belong to birds instead on the basis of their length of around and bird-like structure. In 2024, the describers of the genus Inabtanin reported a partial right humerus of a large pterosaur in the Ruseifa Phosphate Mines, near the Jordanian capital of Amman, which was where the holotype of Arambourgiania was recovered. They concluded that the specimen belonged to A. philadelphiae and that it is comparable in size and shape to the humerus of the type species of Quetzalcoatlus, Q. northropi. North America On 15 August 1982, Ralph Johnson unearthed an azhdarchid cervical vertebra (YPM VPPU 023497) from rock layers of the Maastrichtian-aged Navesink Formation located in Monmouth County, New Jersey in the United States. In 1983, this vertebra was referred to Titanopteryx (=Arambourgiania) sp. on the basis of its elongation and lateral compression, though it is extremely poorly preserved. The assignment of this specimen came into question in the 2025 description of Infernodrakon, where the authors considered the specimen as aff. Arambourgiania sp. (meaning that it has affinity to an undetermined species of Arambourgiania) due to its broader cross section than the known specimens of Arambourgiania and the lack of further study of the fossil. Between 1971-73, two amateur fossil collectors John Brzostoski and Harold Mendryk discovered a cervical vertebra (YPM-PU 21820), a humerus (YPM-PU 22359), and an associated femur and tibia (YPM-PU 21821) in the Early Campanian-aged Merchantville Formation of New Castle County, Delaware in the United States. Initially described as pterosaur specimens that are similar to Pteranodon, while Averianov identified them as indeterminate azhdarchids in 2014. In 2021, Averianov and colleagues suggested that the cervical vertebra (YPM-PU 21820) belongs to a pteranodontid or even Pteranodon itself based on its pneumaticity, a referral also suggested previously by Bennett (1994) and Barrett and colleagues (2008). In 1999, a fragmentary azhdarchid cervical vertebra (MPPM 2000.23.1) was discovered by Memphis local Wendy Melton-Beeson and collected by paleontologist T. Lynn Harrell Jr. that same year. The cervical vertebra had been taken from rocks in Selmer, Tennessee belonging to the lower Coon Creek Formation, dating to late Campanian in age, older than the Maastrichtian-aged remains found in Jordan. whereas in 2022, American paleontologist Gregory S. Paul stated that it may not belong to Arambourgiania. In 2025, the describers of Infernodrakon considered this specimen as Arambourgiania sp. but not A. philadelphiae due to the morphological differences and temporal separation from the holotype. This same study also noted morphological similarities between MPPM 2000.23.1 and YPM VPPU 023497 from the Navesink Formation. ==Description==

Arambourgiania was among the largest azhdarchids, rivalled in size by Quetzalcoatlus and Hatzegopteryx (and possibly Cryodrakon). and Wellnhopterus), and long-necked taxa with longer, slenderer beaks (i.e. Zhejiangopterus). Of these, Arambourgiania is of uncertain affiliation. Arambourgiania was likely quadrupedal, as indicated by the limb morphology of related species and azhdarchid trackways from South Korea. Fragments of other cervical vertebrae have been unearthed in Jordan as well as in the United States, though none is as complete as the holotype. A fragment of a neural arch from either an anterior dorsal (back) vertebra or a posterior cervical vertebra, but it is too incomplete and worn to surmise much information. Applying that 1.18 ratio to the overall size, Frey and Martill concluded in the late 1990s that the wingspan of Arambourgiania was , larger than the estimated wingspan of Quetzalcoatlus, which measured . This would have made Arambourgiania the largest pterosaur known. In 1997, paleontologist Lorna Steel and colleagues reconstructed a life-sized skeleton of Arambourgiania based on better-known related pterosaurs. They set its wingspan at , within the range of Frey and Martill's estimate. In 2010, paleontologists Mark Witton and Michael Habib argued that a wingspan is an underestimate for Arambourgiania, while a wingspan would be too much. In his 2022 pterosaur book, Paul proposed that Arambourgiania had a wingspan of , making it smaller than Quetzalcoatlus northropi, which he kept at . He also suggested that Arambourgiania had a smaller wingspan than Hatzegopteryx from Romania, which Paul situated at . Just like both Arambourgiania and Quetzalcoatlus, Hatzegopteryx is also among the largest known flying animals to ever exist. In a 2024 study, the wingspan of Arambourgiania was estimated to be around based on a large humerus comparable in size to that of Q. northropi. This new estimate is slightly larger than Paul's 2022 estimate, but does not surpass the wingspan of Quetzalcoatlus. In 2018, the "Sidi Chennane Azhdarchid" ulna that was assigned to Arambourgiania was estimated to be smaller than other Arambourgiania individuals, with a wingspan of around . ==Classification==

(A), and Quetzalcoatlus lawsoni'' (D), with known parts in gray Arambourgiania was assigned to a newly named subfamily called Azhdarchinae by Nessov in 1984, though it was still known as "Titanopteryx" at that time. Azhdarchinae also included the pterosaurs Azhdarcho and Quetzalcoatlus. Nessov assigned the Azhdarchinae to the family Pteranodontidae based on their toothless beaks. Unaware of the creation of Azhdarchinae, American paleontologist Kevin Padian created the family Titanopterygiidae, which included both "Titanopteryx" and Quetzalcoatlus. Titanopterygiidae was united based on the shape and proportions of the cervical vertebrae, and was differentiated from Pteranodontidae. However, several other studies instead favored a closer relationship between Arambourgiania and the azhdarchids Mistralazhdarcho and Aerotitan. Below are two cladograms from different studies that show the position of Arambourgiania within Azhdarchidae. The first cladogram is based on the phylogenetic analysis by American paleontologist Brian Andres in 2021, which places Arambourgiania as the sister taxon of Quetzalcoatlus. The second cladogram is based on the 2023 study by paleontologist Rubi Pêgas and colleagues and placed Arambourgiania in a trichotomy with Mistralazhdarcho and Aerotitan. Topology 1: Andres (2021). Topology 2: Pêgas and colleagues (2023). }} }} }} }} ==Paleobiology==

Feeding and ecological niche The ecological niche of azhdarchids have been debated among paleontologists. Mark Witton and Darren Naish noted in 2008 that azhdarchids have been historically considered as scavengers, aerial predators, stork-like generalists, or marine piscivores (fish-eaters) with similar methods of feeding seen in modern birds (i.e. probing, wading, swimming, etc.). Witton and Naish noted that it is unlikely for azhdarchids to have had a piscivorous lifestyle similar to modern skim-feeders like skimmers and some terns, which feed by trawling their lower jaws through water while flying and catching prey from the surface. Azhdarchids lacked cranial features such as sideways compressed lower jaws and the shock-absorbing adaptations required for this mode of feeding, and their jaws instead appeared to have been almost triangular in cross-section, unlike those of skim-feeders and probers. Locomotion Historically, azhdarchids have been interpreted as soarers, although some authors have suggested that their musculature allowed flapping flight like in swans and geese. Their short and potentially broad wings may have been suited for flying in terrestrial environments, as similar wing shapes can be found in large, terrestrially soaring birds. Albatross-like soaring has also been suggested, but in 2013, Witton considered this unlikely because of their supposed predominance in terrestrial environments and their adaptations for foraging on the ground. Studies of azhdarchid flight abilities indicate that they would have been able to fly for long and probably fast, especially if they had an adequate amount of fat and muscle as nourishment, so that geographical barriers would not present obstacles. One long trackway of this kind shows that azhdarchids walked with their limbs held directly underneath their body, and along with the morphology of their feet indicates they were more proficient on the ground than other pterosaurs. Neck biomechanics The lithe, thin-walled vertebrae of Arambourgiania indicate the neck was much weaker than that of Hatzegopteryx. This can be quantified using relative failure force, which is the bone failure force of a vertebra divided by the body weight of the pterosaur that it belongs to, estimated at for Arambourgiania and Hatzegopteryx. While Arambourgiania's neck vertebrae fail at about half of its body weight, the posterior neck vertebrae of Hatzegopteryx can withstand anywhere between five and ten body weights, depending on the loading of the bone. Even the hypothetically longer anterior neck vertebrae of Hatzegopteryx would be able to withstand four to seven body weights. Although the centrum of Arambourgiania is much more lighltly built than that of Hatzegopteryx, their ratios of bone radius to bone thickness (R/t) are roughly the same (9.45 for Hatzegopteryx and 9.9 for Arambourgiania). This may represent a compromise between increasing bending strength and buckling strength. Higher R/t ratios lead to improved bending strength, but weaker buckling strength. To compensate for this, Hatzegopteryx shows a number of other adaptations to improve buckling strength, namely the distinctive internal structures of the bones and the large articular joints of the vertebrae, the latter of which helps to distribute stress. In order to support the robust head, the neck of Hatzegopteryx was likely strongly muscled, in contrast to that of Arambourgiania with its fewer muscle attachments. == Paleoecology ==

and the Middle East during the Maastrichtian, showing the extent of the Tethys Sea.Fossils of Arambourgiania are confidently known only from Ruseifa, Jordan, though specimens potentially belonging to the genus have been described from Morocco and the Southern United States as well. In Jordan and Morocco, Arambourgiania fossils come from sites that during the Maastricthian were covered by the Tethys Sea. This was a large sea extending across Europe, the Middle East, and North Africa during the Late Cretaceous and Paleogene. Other Maastrichtian-aged azhdarchoids are known from the Tethys Sea as well, including Inabtanin from Jordan, Phosphatodraco from Morocco, and indeterminate azhdarchids from Spain and France. Labeled as the Ruseifa Formation, or a deep marine environment. This faunal composition is very similar to that of the Maastrichtian of Syria and the rest of the Mediterranean Tethys Sea. == See also ==