Arambourgiania

Arambourgiania Temporal range: Maastrichtian PreꞒ Ꞓ O S D C P T J K Pg N
Holotype fossil cast at Museum Histoire Naturelle, Paris
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Order:	†Pterosauria
Suborder:	†Pterodactyloidea
Family:	†Azhdarchidae
Subfamily:	†Quetzalcoatlinae
Genus:	†Arambourgiania Nessov vide Nessov & Yarkov, 1989
Species:	†A. philadelphiae
Binomial name
†Arambourgiania philadelphiae (Arambourg, 1959)
Synonyms
Genus synonymy Titanopteryx Arambourg, 1959 (preoccupied) Species synonymy Titanopteryx philadelphiae Arambourg, 1959

Arambourgiania is an extinct genus of azhdarchid pterosaur from the Late Cretaceous period (Maastrichtian stage) of Jordan, and possibly the United States and Morocco.^[1][2] With a wingspan of around 10 metres (33 ft), Arambourgiania was among the largest members of its family, the Azhdarchidae, and it is also one of the largest flying animals ever known.^[3]

In the early 1940s, a railway worker during repairs on the Amman-Damascus railroad near Russeifa found a two foot long fossil bone. In 1943 this was acquired by the director of a nearby phosphate mine, Amin Kawar, who brought it to the attention of a British archeologist, Fielding, after the war. This generated some publicity — the bone was even shown to Abdullah I of Jordan — but more importantly, it made the scientific community aware of the find.

In 1953 the fossil was sent to Paris, where it was examined by Camille Arambourg of the Muséum national d'histoire naturelle. In 1954, he concluded the bone was the wing metacarpal of a giant pterosaur. In 1959, he named a new genus and species: Titanopteryx philadelphiae. The genus name meant "titan wing" in Greek; the specific name refers to the name of Amman in Antiquity: Philadelphia. Arambourg let a plaster cast be made and then sent the fossil back to the phosphate mine; this last aspect was later forgotten and the bone was assumed lost.

In 1975 Douglas A. Lawson, studying the related Quetzalcoatlus, concluded the bone was not a metacarpal but a cervical vertebra.

In the eighties, Russian paleontologist Lev Nesov was informed by an entomologist that the name Titanopteryx had already been given by Günther Enderlein to a fly from the Simulidae family in 1935. Therefore, in 1989 he renamed the genus into Arambourgiania, honoring Arambourg. However, the name "Titanopteryx" was informally kept in use in the West, partially because the new name was assumed by many to be a nomen dubium.

Early 1995, paleontologists David Martill and Eberhard Frey traveled to Jordan in an attempt to clarify matters. In a cupboard of the office of the Jordan Phosphate Mines Company they discovered some other pterosaur bones: a smaller vertebra and the proximal and distal extremities of a wing phalanx — but not the original find. However, after their departure to Europe engineer Rashdie Sadaqah of the mine investigated further and in 1996 established it had been bought from the company in 1969 by geologist Hani N. Khoury who had donated it in 1973 to the University of Jordan; it was still present in the collection of this institute and now could be restudied by Martill and Frey.

Frey and Martill rejected the suggestion that Arambourgiania was a nomen dubium or identical to Quetzalcoatlus and affirmed its validity in relation to "Titanopteryx".

Nesov in 1984 had placed the species within Azhdarchinae, back then part of the Pteranodontidae; the same year Kevin Padian placed it within Titanopterygidae. Both concepts have fallen into disuse now that such forms are commonly assigned to the Azhdarchidae.

In 2016, an azhdarchid cervical vertebra (MPPM 2000.23.1) was described from the Coon Creek Formation of McNairy County, Tennessee and referred to Arambourgiania philadelphiae, which may potentially extend the geographic range of Arambourgiania to North America.^[1] This specimen was later referred to as cf. Arambourgiania.^[4]

In 2018, topotype specimens were located in Bavarian State Collection for Palaeontology and Geology in Munich, Germany that were placed there in 1966 from Jordan and probably represent additional elements of the holotype individual. These are identified as cf. Arambourgiania and include the "fragments of two cervical vertebrae, a neural arch, a left femur, a ?radius, and a metacarpal IV" and other indeterminate fragments.^[5] The incomplete left ulna of the "Sidi Chennane azhdarchid" from Morocco has also been identified as cf. Arambourgiania.^[2]

In 2024, the describers of Inabtanin discovered a large partial right humerus of A. philadelphiae from the Ruseifa Phosphate Mines, near the Jordanian capital of Amman, where the holotype was recovered. The specimen is comparable in size and shape to the humerus of Quetzalcoatlus northropi.^[3]

The holotype, VF 1, consists of a very elongated cervical vertebra, probably the fifth. Today the middle section is missing; the original find was about 62 cm (24 in) long, but had been sawed into three parts. Most of the fossil consists of an internal infilling or mold; the thin bone walls are missing on most of the surface. The find had not presented the whole vertebra; a piece was absent from its posterior end as well.

Frey and Martill estimated the total length to have been 78 cm (31 in), using for comparison the relative position of the smallest shaft diameter of the fifth cervical vertebra of Quetzalcoatlus. From this again the total neck length was extrapolated at about 3 m (9.8 ft). From the relatively slender vertebra the length dimension was then selected to be compared to that of Quetzalcoatlus, estimated at 66 cm (26 in) long, resulting in a ratio of 1.18. Applying that ratio to the overall size, Frey and Martill in the late 1990s concluded that the wingspan of Arambourgiania had been 11–13 m (36–43 ft), compared with the 10–11 m (33–36 ft) wingspan of Quetzalcoatlus, and that Arambourgiania was thus the largest pterosaur then known.^[6][7]

However, the estimate proposed by Frey and Martill was taken into question and the later estimates of wingspan have been more moderate, for the remains are too fragmentary to estimate a gigantic size. The researchers who described Phosphatodraco stated that the wingspan of Arambourgiania was more likely at 7 m (23 ft), but this estimate was not given a rationale.^[8] In 2010, Mark Witton and Michael Habib argued that a 7 m (23 ft) wingspan is an underestimate, while a 11–13 m (36–43 ft) wingspan is an overestimate.^[9] In 2022, Gregory S. Paul proposed that Arambourgiania had a wingspan of 8–9 m (26–30 ft), smaller than that of Quetzalcoatlus or Hatzegopteryx.^[10] In a 2024 study, based on a large humerus comparable in size to that of Quetzalcoatlus northropi, the wingspan of Arambourgiania was estimated around 10 metres (33 ft).^[3]

Below is a cladogram showing the phylogenetic placement of Arambourgiania within the clade Neoazhdarchia. The cladogram is based on a topology recovered by Brian Andres and Timothy Myers in 2013.^[11]

A 2024 description of its humerus compared it to that of soaring birds, suggesting that Arambourgiania was a soarer. This is in contrast to the contemporary Inabtanin, which is closer to those of continuously flapping birds.^[3]

• List of pterosaur genera
• Timeline of pterosaur research
• Pterosaur size

• Arambourg, C. (1959). "Titanopteryx philadelphiae nov. gen., nov. sp. Ptérosaurien géant." Notes Mém. Moyen-Orient, 7: 229–234.
• Frey, E. & Martill, D.M. (1996). "A reappraisal of Arambourgiania (Pterosauria, Pterodactyloidea): One of the world's largest flying animals." N.Jb.Geol.Paläont.Abh., 199(2): 221–247.
• Martill, D.M., E. Frey, R.M. Sadaqah & H.N. Khoury (1998). "Discovery of the holotype of the giant pterosaur Titanopteryx philadelphiae Arambourg 1959, and the status of Arambourgiania and Quetzalcoatlus." Neues Jahrbuch fur Geologie und Paläontologie, Abh. 207(1): 57–76.
• Nessov, L.A., and Yarkov, A.A. (1989). "New Cretaceous-Paleogene birds of the USSR and some remarks on the origin and evolution of the class Aves". Trudy Zoologicheskogo Instituta AN SSSR, 197: 78–97. [In Russian]
• Steel, L., D.M. Martill., J. Kirk, A. Anders, R.F. Loveridge, E. Frey, and J.G. Martin (1997). "Arambourgiania philadelphiae: giant wings in small halls." The Geological Curator, 6(8): 305–313.