Diplodocus now common scientific opinion that "Seismosaurus hallorum" is a species of "Diplodocus". This genus of dinosaurs lived in what is now mid-western North America at the end of the Jurassic period. "Diplodocus" is one of the more common dinosaur fossils found in the middle to upper Morrison Formation, between about 154 and 152 million years ago, during the late Kimmeridgian age. The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs, such as "Apatosaurus", "Barosaurus", "Brachiosaurus", "Brontosaurus", and "Camarasaurus". "Diplodocus" is among the most easily identifiable dinosaurs, with its typical sauropod shape, long neck and tail, and
Dinosaur Park dinosaurs at the now closed Dinosaur World in Beaver, Arkansas. The park is located at 940 Skyline Drive and is maintained by the city of Rapid City. Admission is free, however steep flagstone stairs may limit handicapped accessibility. The park was listed on the National Register of Historic Places on June 21, 1990. Dinosaurs represented in the park include "Apatosaurus", "Tyrannosaurus rex", "Triceratops", "Stegosaurus", and an "Edmontosaurus annectens" (formerly "Anatotitan" which itself formerly "Trachodon"). A "Protoceratops" and a "Dimetrodon" ("Dimetrodon" is not actually a dinosaur, but rather a synapsid, and more closely related to mammals than reptiles) were added later