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.
Dinosaur
The smallest dinosaur known is the bee hummingbird, with a length of only and mass of around . The smallest known non-avialan dinosaurs were about the size of pigeons and were those theropods most closely related to birds. For example, "Anchiornis huxleyi" is currently the smallest non-avialan dinosaur described from an adult specimen, with an estimated weight of 110 grams and a total skeletal length of . The smallest herbivorous non-avialan dinosaurs included "Microceratus" and "Wannanosaurus", at about long each.