Haplocanthosaurus (Saurischia: Sauropoda) from the lower Morrison Formation (Upper Jurassic) near Snowmass, Colorado

Abstract

A small sauropod dinosaur collected from the Rocky Mountains of central Colorado (north of the Elk Range, Pitkin County) is assigned to the rare genus Haplocanthosaurus. The specimen, MWC 8028, consists of four dorsal centra, five partial ribs, the sacrum, five caudal vertebrae, three chevrons, five partial neural spines and many fragments and is from the lower third of the Upper Jurassic Morrison Formation. The dorsal vertebrae are procamerate, and on the sacral vertebrae the neural arch peduncles are vertically elongate and the neural spines are strongly reclined. The only sauropod from the Morrison Formation that shares these characters is Haplocanthosaurus and based on those characters MWC 8028 is referred to Haplocanthosaurus. This is at most the tenth specimen and the seventh locality for this sauropod, all within the Morrison Formation.