Supersaurus

Supersaurus was a sauropod dinosaur, a relative of "Diplodocus". It was found in the Upper Jurassic Morrison Formation of Colorado in 1972. 
In most respects, "Supersaurus" is similar in to "Apatosaurus", but it is less robustly built. It has elongated cervical vertebrae, resulting in one of the longest known sauropod necks. It was up to 33 to 34 meters (108 to 112 ft) in length, and a weight of 35 to 40 tons. 
A new and much more complete specimen of "Supersaurus", nicknamed 'Jimbo', WDC DMJ-021, was found in Converse County, Wyoming in 1996. It is currently being prepared and was described in 2007. Its bones are held at the Wyoming Dinosaur Center.