with the reconstructed front leg of
Ultrasauros Supersaurus is present in stratigraphic zone 5 of the Morrison, dating from the
Tithonian. The original
fossil remains of
Supersaurus were discovered in the
Dry Mesa Quarry in 1972. This find yielded only a few bones: mainly the shoulder girdle, an
ischium, and tail vertebrae. Paleontologist
James A. Jensen described
Supersaurus; he designated a
scapulocoracoid BYU 9025 (originally labeled as BYU 5500) as the
type specimen. This shoulder girdle stood some tall, if placed on end. The specimen was given the name "Supersaurus" informally as early as 1973, but was not officially described and named until more than a decade later, in 1985. A much more complete specimen WDC DMJ-021, was found in
Converse County,
Wyoming in 1986 by Brandon Flyr and Bart Lesco while out hiking and was reported to the people who owned the land at the time. The discovery was later named "Jimbo" in 1996 by the family that purchased the land, it was described and assigned to
Supersaurus in 2007. The specimen represented approximately 30% of the skeleton. Its bones are being held at the
Wyoming Dinosaur Center. A comparison of WDC DMJ-021 and other specimens previously assigned to
Supersaurus was done in order to help decide what material from the Dry Mesa Quarry belonged to the genus. It indicated that a series of tail vertebrae and an ulna may have belonged to some other diplodocid. (later renamed
Ultrasauros macintoshi). The type specimen (the specimen used to define a new
species) of
Ultrasauros, being a backbone (dorsal
vertebra, labeled BYU 9044), was later found to have come from
Supersaurus. In fact, it probably belonged to the original
Supersaurus specimen, which was discovered in the same quarry in 1972. Therefore,
Ultrasauros became a
junior synonym of
Supersaurus, which had been named first and thus retains priority, and the name
Ultrasauros was abandoned. Other bones that were found at the same location and originally thought to belong to
Ultrasauros, like a shoulder girdle (
scapulocoracoid, BYU 9462), actually belonged to
Brachiosaurus, possibly a large specimen of
Brachiosaurus altithorax. Originally, these
Supersaurus and
Brachiosaurus bones were believed to represent a single dinosaur that was estimated to reach about long, high at the shoulder, in total height, and weighing maybe . At the time, mass estimates ranged up to 180 tons, which placed it in the same category as the
blue whale and the equally problematic
Bruhathkayosaurus. The naming of the
chimeric Ultrasauros has a similarly complicated history.
Ultrasaurus (with the final "u") was the original choice, and was widely used by the media after the discovery in 1979. However, the name of a new
species must be published with a description to become official. When it was later discovered that the new name referred to bones from two separate, and already known species, the name
Ultrasauros was considered invalid and became a junior synonym for
Supersaurus. Since the holotype of the
Ultrasaurus was a dorsal vertebrae of the
Supersaurus, so
Ultrasauros is not a junior synonym for
Brachiosaurus. The name
Supersaurus was kept instead of
Ultrasaurus as the animal is a diplodocid and
Ultrasaurus had always referred to a brachiosaurid. ==Description==