Hatzegopteryx

Hatzegopteryx, whose name means "Hațeg basin wing," is a genus of azhdarchid pterosaur known from the late Maastrichtian Densuș-Ciula Formation in Transylvania, Romania. The only recognized species is *Hatzegopteryx thambema*, named in 2002 by Eric Buffetaut, Dan Grigorescu, and Zoltan Csiki from parts of a skull and a humerus. Later finds, including a neck vertebra, have been assigned to the genus and show a range of sizes; the largest suggest a wingspan of 10 to 12 meters (33 to 39 feet), placing it among the biggest pterosaurs. Unlike other giant azhdarchids, *Hatzegopteryx* had a very wide skull with strong attachments for large muscles, bones that were spongy inside rather than hollow, and a short, sturdy, heavily muscled neck only 1.5 meters (5 feet) long—about half the length of similar-sized azhdarchids—that could handle strong bending forces. It lived on Hațeg Island, a subtropical island in the ancient Tethys Sea. With no large theropods present, *Hatzegopteryx* was likely the top predator there, taking on proportionally bigger prey, such as dwarf titanosaurs and iguanodontians, than other azhdarchids. **Discovery and naming**

The first pterosaur remains from Romania were identified by Franz Nopcsa in 1899. The first *Hatzegopteryx* fossils came from a student dig in the late 1970s at Vălioara, in the northwestern Hațeg Basin, from the upper Middle Densuș-Ciula Formation, dated to the late Campanian and early Maastrichtian, around 72 million years ago. The holotype, FGGUB R 1083A, includes two fragments from the back of the skull and the damaged upper part of a left humerus. One fragment, the occipital region, was first thought to be from a theropod dinosaur when announced in 1991. A 38.5 cm (15.2 in) midsection of a femur found nearby, FGGUB R1625, may also belong to *Hatzegopteryx*; if so, it came from a smaller individual with a wingspan of 5 to 6 meters (16 to 20 feet). An unpublished mandible from a large individual was also reported from the same site. The genus was named in 2002 by French paleontologist Eric Buffetaut and Romanians Dan Grigorescu and Zoltan Csiki. The generic name comes from the Hatzeg (Hațeg) basin and the Greek *pteryx* ("wing"). The species name *thambema* is Greek for "terror, monster," referring to its enormous size. Additional specimens have since been found elsewhere. A medium-sized scapulocoracoid from the Sânpetru Formation at Vadu, Sântămăria-Orlea, likely belonged to an individual with a 4.5 to 5 meter (15 to 16 ft) wingspan. From the Râpa Roșie site in the Sebeș Formation, contemporary and adjacent to the Densuș-Ciula Formation, a single large neck vertebra (the "RR specimen" or EME 215) was found. Although no overlapping bones allow a definite assignment to *Hatzegopteryx thambema*, its distinctive internal bone structure and the lack of evidence for another giant azhdarchid in the area support its referral to at least *Hatzegopteryx* sp. **Description**

**Size**

The size of *Hatzegopteryx* was first estimated by comparing its 236 mm (9.3 in) humerus fragment with that of *Quetzalcoatlus northropi*, which has a 544 mm (21.4 in) humerus. Noting the fragment was less than half the original bone, Buffetaut and colleagues thought it could have been "slightly longer" than *Quetzalcoatlus*'s. The wingspan of *Quetzalcoatlus* had been estimated at 11 to 12 meters (36 to 39 ft) in 1981, with earlier estimates as high as 15 to 20 meters (49 to 66 ft). They concluded a 12 meter (39 ft) wingspan for *Hatzegopteryx* was conservative, "provided that its humerus was longer than that of *Q. northropi*." In 2010, Mark Witton and Michael Habib concluded *Hatzegopteryx* was probably no larger than *Q. northropi* in wingspan. The initial estimates did not account for bone distortion. The wingspan is generally estimated at 10 to 11 meters (33 to 36 ft). It has been suggested, based on the wide, robust neck vertebra referred to *Hatzegopteryx*, that the entire vertebral column was similarly expanded, increasing overall size. However, this is likely not true, as neck vertebrae in large pterodactyloids tend to be wider and larger than other vertebrae. Although size estimates from vertebrae alone are not very reliable, the vertebra's size is consistent with an animal of 10 to 12 meters (33 to 39 ft) wingspan. **Skull**

The skull of *Hatzegopteryx* was gigantic, estimated at 2.5 meters (8 ft 2 in) long based on comparisons with *Nyctosaurus* and *Anhanguera*, making it one of the largest skulls among non-marine animals. The rear of the skull was broad, 0.5 meters (1 ft 8 in) wide across the quadrate bones. While most pterosaur skulls consist of thin plates and struts, *Hatzegopteryx* had stout, robust skull bones with large ridges indicating strong muscle attachments. In 2018, Mátyás Vremir concluded that *Hatzegopteryx* likely had a shorter, broader skull, which he estimated at 1.6 meters (5 ft 3 in), and a smaller wingspan of 8 meters (26 ft).