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.
Compsognathidae
Compsognathids are considered to be among the smallest dinosaurs ever discovered. "Compsognathus longipes" was largely acknowledged to the smallest dinosaur and was around the size of a chicken when fully grown. The specimens found indicate that this species was around 1 m long and weighed 2.5 kg. However, recently other adult dinosaur specimen have now been found that are smaller than Compsognathus, including the dinosaurs "Caenagnathasia", "Microraptor", and "Parvicursor", all of which are estimated to be less than 1m long. Most of these specimen are incomplete, so size determination is still just an estimate.