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.
Mamenchisaurus
In 1993, "M. sinocanadorum" was described, which consisted of skull material and the first four cervical vertebrae. This species possessed the longest cervical rib of any described sauropod dinosaur, measuring . This is longer than the longest "Sauroposeidon" cervical rib, which measures . Additional remains attributed to this species, but not yet formally described, belong to one of the largest dinosaurs known—the restored skeleton measuring in length with a neck measuring nearly long.