page_title: Haplocanthosaurus
section_title: Discovery
hierarchical_section_title: Haplocanthosaurus / Discovery
caption_attribution_description: English: Diagram of west end of that portion of bone quarry near Canyon City, Colo., worked by W. H. Utterback, showing the positions in which the types of Haplocanthosaurus priscus (No. 572, A, B, C) and H. utterbackii (=H. priscus; No. 879) were found. The shaded bones pertain to a different genus. A. 572 femur, pelvis, sacrum and nineteen anterior caudals&#160;; B. 572 nine posterior dorsals&#160;; C. 572 first dorsal and last two cervicals.
context_page_description: Haplocanthosaurus is a genus of intermediate sauropod dinosaur. Two species, H. delfsi and H. priscus, are known from incomplete fossil skeletons. It lived during the late Jurassic period, 155 to 152 million years ago. The type species is H. priscus, and the referred species H. delfsi was discovered by a young college student named Edwin Delfs in Colorado, USA. Haplocanthosaurus specimens have been found in the very lowest layer of the Morrison Formation, along with Hesperosaurus, Brontosaurus yahnahpin, and Allosaurus jimmadseni.
context_section_description: There are four known specimens of Haplocanthosaurus: one of H. delfsi, and three of H. priscus. Of these, the type of H. delfsi is the only one complete enough to mount. The mounted specimen of H. delfsi now stands in the Cleveland Museum of Natural History, albeit with a completely speculative replica skull, as the actual skull was not recovered. Present in stratigraphic zones 1, 2, and 4. Recently described specimens from a different region of the Morrison Formation were assigned to Haplocanthosaurus in 2014. The study describing them noted that Haplocanthosaurus is known for certain from at least four specimens, assigned to H. priscus (CM 572), H. utterbacki (=H. priscus; CM 879), H. delfsi (CMNH 10380), and H. sp. (MWC 8028). Up to seven additional specimens have been assigned to Haplocanthosaurus? or Haplocanthosauridae indet. One potential specimen has been nicknamed "Big Monty," for its discovery in Montana. It's been claimed to measure an incredible 110 feet (33 meters) long. However, much controversy surrounds the specimen and, as such, little is truly known about it.
caption: Quarry map showing holotype of H. priscus
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