Haplocanthosaurus comes under the family of sauropod , the two species found out till date known to be the , H. delfsi and H. priscus have fossils which possess only partial fragments of the skeletons, The Haplocanthosaurus were believed to have survived in the Juarraic period about 155 to 152 million years before apprimately.
Amazingly another species known to be the H.delfsi was recovered through a young college student Edwin Delfs from Colorado a province of United States. The Haplocanthosaurus originates from the bottom most layer in Morrison Formation coupled together with many more species of Hesperosaurus, Eobrontosaurus, and Allosaurus jimmadensi.
The animal is believed to be the smaller one out of all the specimens in the sauropod category , The maximum length an average Morisson saurapod might grow is calculated to be approximately 20 meters But the Haplocanthosaurus has a length summed up to 14.8 meters and weighs 12.8 metric tons which proves it to be smaller than the other members of the sauropod family.
The well known species of the Haplocanthosaurus total up to a sum of four out of which one is H. delfsi and the rest of the three are species of H. priscus, Out of all other specimens only the type species oh H. delfsi could be constructed properly. The entire construction of the H. delfsi can be found in Cleveland Museum of Natural History but the skull part is not original since it could not be discovered till now , the skull part alone is an artificially made one.