Because of fragmentary remains it was, and still is, a bit obscure and with the discovery of a second species aspersions were cast on its classification. These new but oh so familiar bones were initially thought to belong to a sauropod but when the dust settled Hypsibema's family ties were confirmed. It was potentially fifteen meters long and twelve tons, which would plonk it almost in the same league as Asia's colossus, Shantungosaurus.
Hypsibema missouriensisFirst discovered in lumps of clay by L. Chronister in 1942, a total of fourteen huge vertebrae eventually found their way to the Smithsonian via "Dinosaur Dan" with a $50 sweetener that the Chronister's used to secure the services of a cow.
Upon initial inspection of these remains, from what turned out to be the Ripley Formation of Bollinger county, Charles Gilmore supposed they belonged to a modestly sized sauropod and, in 1945, he named Neosaurus missouriensis. As it turns out, this name was occupied by Nopsca's pelycosaur so Neosaurus was renamed Parrosaurus (honoring Albert Eide Parr) later that year, but Gilmore's research was hampered somewhat by the fact that he died shortly after.
After further study by Baird and Horner in 1979, Parrosaurus was lumped with Hypsibema as H.missouriensis (named for Missouri and the Latin "ensis" meaning "from" ), a move met with much scepticism, and it wasn't until more discoveries by Drs. Stinchcomb, Parris, and Grandstaff in the 1980's that the true identity of the creature was realized. Cope was right; Hypsibema was a huge duck-billed hadrosauroid.
Despite several name changes and genus jumps the status of Hypsibema missouriensis is anything but certain, but its fragmentary nature made it a shoo-in as someone's official state dinosaur and Missouri adopted it in 2004.