Quetzalcoatlus is a genus of pterosaur known from the Late Cretaceous period of North America (Maastrichtian stage); its members were among the largest known flying animals of all time. Quetzalcoatlus is a member of the Azhdarchidae, a family of advanced toothless pterosaurs with unusually long, stiffened necks. Its name comes from the Aztec feathered serpent god Quetzalcoatl. The type species is Q. northropi, named by Douglas Lawson in 1975; the genus also includes the smaller species Q. lawsoni, which was known for many years as an unnamed species before being named by Brian Andres and Wann Langston Jr. (posthumously) in 2021. Discovery and species The first Quetzalcoatlus fossils were discovered in Texas, United States, from the Maastrichtian Javelina Formation at Big Bend National Park (dated to around 68 million years ago) in 1971 by Douglas A. Lawson, then a geology graduate student from the Jackson School of Geosciences at the University of Texas at Austin. The specimen consisted of a partial wing (in pterosaurs composed of the forearms and elongated fourth finger), from an individual later estimated at over in wingspan. Lawson discovered a second site of the same age, about 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, who drove the development of large tailless flying wing aircraft designs resembling Quetzalcoatlus. 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 . This species was named Q. lawsoni in 2021, named