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.
Dallasaurus
Dallasaurus ("Dallas lizard") is a basal mosasauroid from the Upper Cretaceous of North America. Along with "Russellosaurus", "Dallasaurus" is one of the two oldest mosasauroid taxa currently known from North America. This small semi-aquatic lizard measured less than a meter in length, compared to such gigantic derived mosasaurs as "Tylosaurus" and "Mosasaurus", each exceeding 14 meters.