Sauroposeidon
The fossils were found in rocks dating from near the end of the Lower Cretaceous (Aptian–early Albian), from about 113 to 110 million years ago.  Sauroposeidon was the last known North American sauropod before an absence on the continent of about 40 million years. The absence of sauropods ended with the appearance of Alamosaurus'' during the last (Maastrichtian) stage at the end of the Cretaceous.