Diplodocoidea

Diplodocoidea is a superfamily of sauropod dinosaurs, which included some of the longest animals of all time, including slender giants like Supersaurus, Diplodocus, Apatosaurus, and Amphicoelias. Most had very long necks and long, whip-like tails; however, one family (the dicraeosaurids) are the only known sauropods to have re-evolved a short neck, presumably an adaptation for feeding low to the ground. This adaptation was taken to the extreme in the highly specialized sauropod Brachytrachelopan. A study of snout shape and dental microwear in diplodocoids showed that the square snouts, large p

Haplocanthosaurus (meaning "simple spined lizard") 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 (Kimmeridgian stage), 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