Haplocanthosaurus priscus

Haplocanthosaurus is a genus of diplodocoid sauropod dinosaur. Two species, H. delfsi and H. priscus, are known from incomplete fossil skeletons. They lived during the Late Jurassic, 155 to 152 million years ago in North America. The type species is H. priscus, named in 1903 John Bell Hatcher , and the referred species H. delfsi was discovered by a young college student named Edwin Delfs in Colorado, United States and described by Jack McIntosh and Michael Williams in 1988. Haplocanthosaurus specimens have been found in the lowermost layer of the Morrison Formation, along with Hesperosaurus mjosi, Brontosaurus yahnahpin, and Allosaurus jimmadseni.