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.
Puertasaurus
"Puertasaurus" was a very large animal. Its size is difficult to estimate due of the scarcity of its remains, but modern estimates place it around long and in mass. The largest of the four preserved bones is the dorsal vertebra, which at wide is the broadest known vertebra of any sauropod. The Cerro Fortaleza Formation is of uncertain age, due to the inconsistency of stratigraphic nomenclature in Patagonia. When "Puertasaurus" was alive, the Cerro Fortaleza Formation would have been a humid, forested landscape. "Puertasaurus" would have shared its habitat with other dinosaurs, including another large sauropod, "Dreadnoughtus", in addition to other reptiles and fish.