Supersaurus (meaning "super lizard") is a genus of diplodocid sauropod dinosaur that lived in North America during the Late Jurassic period. The type species, S. vivianae, was first discovered by Vivian Jones of Delta, Colorado, in the middle Morrison Formation of Colorado in 1972. The fossil remains came from the Brushy Basin Member of the formation, dating between 153 and 145 million years ago. It is among the longest dinosaurs ever discovered, with the three known specimens reaching in length, with the largest individual possibly exceeding in size. Mass estimates for the WDC and BYU specimens tend to be around in body mass. 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

thumb|Diagram showing the size of Supersaurus (orange) compared with selected giant sauropods

Supersaurus is among the largest dinosaurs known from good remains and quite possibly the longest discovered thus far, with the WDC specimen reaching in length, the BYU specimen reaching perhaps and a third specimen potentially exceeding in size.

thumb|left|Life restoration of Supersaurus based primarily on [[Wyoming Dinosaur Center's more complete "Jimbo"]]

A study in 2024 also found the Jimbo specimen to be skeletally mature at the time of its death and among the oldest known dinosaurs. While the result obtained was 225 years, the study strongly states that a value this high is extremely unlikely and more reflects the limitations of the methodology in calculating the age of exceptionally old individuals.<!-- cannot verify 45 m from the cited sources. 45 m is not mentioned in the papers --> This vertebra measures in length and is the longest cervical known. This enormous vertebra was reclassified as a Barosaurus vertebra, by Mike Taylor and Matt Wedel. However Brian Curtice has reassigned it to Supersaurus on the basis of additional specimens. Michael Benton also agreed with the reclassification, giving the Supersaurus BYU 9024 specimen an approximate length of up to an impressive , which would have made it the longest animal to ever live.

The assignment of the more complete specimen, WDC DMJ-021, to Supersaurus suggests that in most respects it was very similar in anatomy to Apatosaurus but less robustly built with especially elongated cervical vertebrae, resulting in one of the longest-known sauropod necks.

thumb|Pelvis of Supersaurus

thumb|Caudal vertebrae and chevrons

In 2015, a specimen-level phylogenetic study of diplodocids found that Dinheirosaurus lourinhanensis grouped with Supersaurus. The study considered that it should be a new species of Supersaurus, in a new combination S. lourinhanensis.

References

  • "Why do mass estimates vary so much?", by Mike Taylor, August 27, 2002. (see footnote)