Thành viên:Kiệt Gì Cũng Biết/nháp

Kiệt Gì Cũng Biết/nháp
Khoảng thời gian tồn tại: Late Cretaceous (Maastrichtian),
Restored Quetzalcoatlus skeleton displayed in quadrupedal stance, Houston Museum of Natural Science
Phân loại khoa học
Vực:	Eukaryota
Giới:	Animalia
Ngành:	Chordata
Lớp:	Reptilia
Bộ:	†Pterosauria
Phân bộ:	†Pterodactyloidea
Họ:	†Azhdarchidae
Chi:	†Quetzalcoatlus Lawson, 1975
Loài điển hình
†Quetzalcoatlus northropi Lawson, 1975
Other species
†Q. lawsoni Andres and Langston Jr., 2021

Quetzalcoatlus /kɛtsəlkoʊˈætləs/ là một loài thuộc chi thằng lằng bay azhdarchid pterosaur thường được tìm thấy ở kỷ phấn trắng muộn Maastrichtian ở Bắc Mỹ. Tên của nó được đặt dựa theo vị thần rắn của người Aztecthe Quetzalcoatl. Loài điển hình là Q. northropi, được đặt tên bởi Douglas Lawson vào năm 1975 theo tên của một nhà thiết kế máy bay Jack Northrop. Chi này cũng bao gồm loài nhỏ hơn làQ. lawsoni, loài này trong nhiều năm liền không có tên, cho đến khi được đặt bởi Brian Andres và Wann Langston Jr. (truy tặng) Vào năm 2021. Q. northropi đã trở nên nổi tiếng với danh hiệu ứng cử viên sáng giá nhất cho chức danh loài động vật biết bay lớn nhất từng được phát hiện.

Discovery and species

Cast of the holotype humerus

The first Quetzalcoatlus fossils were discovered in Texas from the Maastrichtian Javelina Formation at Big Bend National Park (dated to around 68 million years ago) in 1971 by Douglas A. Lawson, who was then a geology graduate student from the Jackson School of Geosciences at the University of Texas, Austin. He would then go on to become a doctoral student at the University of California, Berkeley. The specimen he discovered consisted of a partial wing (in pterosaurs composed of the forearms and elongated fourth finger) from an individual later estimated at over 10 m (33 ft) in wingspan.

Lawson discovered a second site of the same age, about 40 km (25 mi) from the first, where between 1972 and 1974, he and Professor Wann Langston Jr. of the Texas Memorial Museum unearthed three fragmentary skeletons of much smaller individuals. Lawson in 1975 announced the find in an article in Science. That same year, in a subsequent letter to the same journal, he made the original large specimen, TMM 41450-3, the holotype of a new genus and species, Quetzalcoatlus northropi. The genus name refers to the Aztec feathered serpent god, Quetzalcoatl. The specific name honors John Knudsen Northrop, the founder of Northrop Corporation, who drove the development of large tailless flying wing aircraft designs resembling Quetzalcoatlus.

Skeletal reconstruction of Q. lawsoni.

At first, it was assumed that the smaller specimens were juvenile or subadult forms of the larger type. Later, when more remains were found, it was realized they could have been a separate species. This possible second species from Texas was provisionally referred to as a Quetzalcoatlus sp. by Alexander Kellner and Langston in 1996, indicating that its status was too uncertain to give it a full new species name. The smaller specimens are more complete than the Q. northropi holotype, and include four partial skulls, though they are much less massive, with an estimated wingspan of 5,5 m (18 ft). This species was named Q. lawsoni in 2021, named after the genus' original describer.

The holotype specimen of Q. northropi had not been properly described and diagnosed until 2021 and until then, the status of the genus Quetzalcoatlus was identified as problematic. Mark Witton and colleagues (2010) noted that the type species of the genus—the fragmentary wing bones comprising Q. northropi—represent elements which are typically considered undiagnostic to generic or specific level and that this complicates interpretations of azhdarchid taxonomy. For instance, Witton et al. (2010) suggested that the Q. northropi type material is of generalized enough morphology to be near identical to that of other giant azhdarchids, such as the overlapping elements of the contemporary Romanian giant azhdarchid Hatzegopteryx. This being the case and assuming that Q. northropi can be distinguished from other pterosaurs (i.e., if it is not a nomen dubium), perhaps Hatzegopteryx should be regarded as a European occurrence of Quetzalcoatlus. However, Witton et al. also noted that the skull material of Hatzegopteryx and Q. lawsoni differ enough that they cannot be regarded as the same animal, but that the significance of this cannot be ascertained, given uncertainty over the relationships of Quetzalcoatlus specimens. These issues can only be resolved by Q. northropi being demonstrated as a valid taxon and its relationships with Q. lawsoni being investigated. An additional complication to these discussions is the likelihood that huge pterosaurs, such as Q. northropi, could have made long, transcontinental flights, suggesting that locations as disparate as North America and Europe could have shared giant azhdarchid species. Q. lawsoni was found to be a valid taxon in 2021 and confirmed to belong to the same genus as Q. northropi.

An azhdarchid neck vertebra, discovered in 2002 from the Maastrichtian age Hell Creek Formation, may also belong to Quetzalcoatlus. The specimen, BMR P2002.2, was recovered accidentally when it was included in a field jacket prepared to transport part of a Tyrannosaurus rex specimen. Despite this association with the remains of a large carnivorous dinosaur, the vertebra shows no evidence that it was chewed on by the dinosaur. The bone came from an individual azhdarchid pterosaur estimated to have had a wingspan of 5–5,5 m (16–18 ft).