Alamosaurus
Alamosaurus (; meaning "Ojo Alamo lizard") is a genus of titanosaurian sauropod dinosaurs, containing a single known species, Alamosaurus sanjuanensis, from the late Cretaceous Period of what is now southern North America. Isolated vertebrae and limb bones indicate that it reached sizes comparable to "Argentinosaurus" and "Puertasaurus", which would make it the largest dinosaur known from North America. Its fossils have been recovered from a variety of rock formations spanning the Maastrichtian age of the late Cretaceous period. Specimens of a juvenile "Alamosaurus sanjuanensis" have been recovered from only a few meters below the Cretaceous-Paleogene boundary in Texas, making it among the last surviving non-avian dinosaur species.
Douglas A. Lawson
When the discovery of the fossils was reported in 1975, "Quetzalcoatlus" was the largest flying creature known to have lived. A fellow researcher challenged Lawson's estimates of the dimensions of the wing architecture of "Quetzalcoatlus". However, Lawson responded by demonstrating that while inconsistent with those of modern-day birds, his estimates were consistent with extrapolations of other pterosaurs, such as "Pterodactylus antiquus". In 2010 the U.S. National Park Service described "Quetzalcoatlus" as the world's second-largest known flying creature.