| Supersaurus | |
|---|---|
 | |
| A cast of BYU 9025, a scapulocoracoid, theholotype ofSupersaurus,Dinosaur Journey Museum | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Superfamily: | †Diplodocoidea |
| Family: | †Diplodocidae |
| Subfamily: | †Diplodocinae |
| Genus: | †Supersaurus Jensen, 1985[1] |
| Type species | |
| †Supersaurus vivianae | |
| OtherSpecies | |
| Synonyms | |
Genus synonymy
Species synonymy (S. vivianae)
| |
Supersaurus (meaning "super lizard") is agenus ofdiplodocidsauropoddinosaur that lived inNorth America during theLate Jurassic period. Thetype species,S. vivianae, was first discovered by Vivian Jones ofDelta, Colorado, in the middleMorrison Formation ofColorado in 1972. The fossil remains came from the Brushy Basin Member of the formation, dating between 153 and 145 million years ago.[3] It is among the longest dinosaurs ever discovered, with the three known specimens reaching 33–40 meters (108–131 ft) in length, with the largest individual possibly exceeding 40 meters (130 ft) in size.[4][5] Mass estimates for theWDC andBYU specimens tend to be around 35–44 metric tons (39–49 short tons) in body mass.[5] A potential second species,S. lourinhanensis (Dinheirosaurus), is known fromPortugal and has been dated to a similar time.[6]
Supersaurus is present in stratigraphic zone 5 of the Morrison, dating from theTithonian.[7] The originalfossil remains ofSupersaurus were discovered in theDry Mesa Quarry in 1972. This find yielded only a few bones: mainly the shoulder girdle, anischium, and tail vertebrae. PaleontologistJames A. Jensen describedSupersaurus; he designated ascapulocoracoidBYU 9025 (originally labeled as BYU 5500) as thetype specimen. This shoulder girdle stood some 2.4 meters (7.9 ft) tall, if placed on end. The specimen was given the name "Supersaurus" informally as early as 1973,[8][9] but was not officially described and named until more than a decade later, in 1985.[1] Sauropod researcher Jack McIntosh at one time thought that the BYUSupersaurus material might represent a large species ofBarosaurus but later felt that there was evidence forSupersaurus being a valid genus.[10]
A much more complete specimen WDC DMJ-021, was found inConverse 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 toSupersaurus in 2007. The specimen represented approximately 30% of the skeleton. Its bones are being held at theWyoming Dinosaur Center. A comparison of WDC DMJ-021 and other specimens previously assigned toSupersaurus 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.[11]
Jensen, who described the originalSupersaurus specimen, simultaneously reported the discovery of another gigantic sauropod, which would later be named "Ultrasaurus"macintoshi[1] (later renamedUltrasauros macintoshi). The type specimen (the specimen used to define a newspecies) ofUltrasauros, being a backbone (dorsalvertebra, labeled BYU 9044), was later found to have come fromSupersaurus. In fact, it probably belonged to the originalSupersaurus specimen, which was discovered in the same quarry in 1972. Therefore,Ultrasauros became ajunior synonym ofSupersaurus, which had been named first and thus retains priority, and the nameUltrasauros was abandoned.[12]
Other bones that were found at the same location and originally thought to belong toUltrasauros, like a shoulder girdle (scapulocoracoid, BYU 9462), actually belonged toBrachiosaurus, possibly a large specimen ofBrachiosaurus altithorax.[12] TheBrachiosaurus bones indicate a large, but not record-breaking individual, a little larger than the "Brachiosaurus" brancai (Giraffatitan brancai) mount in theBerlin's Natural History Museum.[13]
Originally, theseSupersaurus andBrachiosaurus bones were believed to represent a single dinosaur that was estimated to reach about 25 to 30 meters (82 to 98 ft) long, 8 meters (26 ft) high at the shoulder, 15 meters (49 ft) in total height, and weighing maybe 70 t (77 short tons). At the time, mass estimates ranged up to 180 tons,[14] which placed it in the same category as theblue whale and the equally problematicBruhathkayosaurus.
The naming of thechimericUltrasauros 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 newspecies must be published with a description to become official.[15]
Before Jim Jensen published his discovery in 1985, another paleontologist, Kim Haang Mook, used the nameUltrasaurus in a 1983 publication to describe what he believed was a giant dinosaur inSouth Korea. This was a different, much smaller dinosaur than Jensen's find, but Kim thought it represented a similarly gigantic animal because he confused ahumerus for anulna. While the logic of naming was incorrect, theUltrasaurus from Kim's find fulfilled the requirements for naming and became regarded as a legitimate, if dubious genus.[13][15] Thus, because Jensen did not publish his own "Ultrasaurus" find until 1985, Kim's use retained its official priority of name, and Jensen was forced to choose a new name (in technical terms, his original choice was "preoccupied" by Kim's sauropod). In 1991, at his suggestion, George Olshevsky changed one letter, and renamed Jensen's sauropodUltrasauros, with the final "o".[16][15]
When it was later discovered that the new name referred to bones from two separate, and already known species, the nameUltrasauros was considered invalid and became a junior synonym forSupersaurus. Since the holotype of theUltrasaurus was a dorsal vertebrae of theSupersaurus, soUltrasauros is not a junior synonym forBrachiosaurus. The nameSupersaurus was kept instead ofUltrasaurus as the animal is a diplodocid andUltrasaurus had always referred to a brachiosaurid.[12]
Anotherdiplodocid dinosaur found near the originalSupersaurus quarry, known from a backbone (dorsalvertebra type specimen BYU 5750), was namedDystylosaurus edwini and is now also considered to be a specimen ofSupersaurus vivianae. Hence,Dystylosaurus has also become a junior synonym ofSupersaurus.[17]
Supersaurus is among thelargest dinosaurs known from good remains and quite possibly the longest discovered thus far, with theWDC specimen reaching 33–36 meters (108–118 ft) in length, theBYU specimen reaching perhaps 39 meters (128 ft) and a third specimen potentially exceeding 40 meters (130 ft) in size.[4][5] TheWDC andBYU specimens are estimated to have weighed 35–44 metric tons (39–49 short tons) in body mass.[5][11][18]
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.[5] The same study found the age of a 33 meters (108 ft)Diplodocus hallorum to be 60 years old, which makes it among the oldest known dinosaurs too, but considered the age of Jimbo to be even greater due to the extensive remodeling of the bone. In fact, the study suggests Jimbo was so old that its exact age cannot be reliably calculated by the applied methodology.[5] Thus, despite the lack of a truly reliable age value, the Jimbo specimen ofSupersaurus can be considered as possibly the oldest dinosaur known thus far. The study also suggests that, due to Jimbo's skeletal maturity, the size range displayed by the three knownSupersaurus specimens, which ranges from 33–40 meters (108–131 ft), can be considered an average adult size for the species.[5]
The first described specimens ofSupersaurus were individual bones that suggested a large diplodocid. A largecervical vertebra BYU 9024 from the same quarry was later assigned toSupersaurus.[19] This vertebra measures 1.38 m (4.5 ft) in length and is the longest cervical known.[20] This enormous vertebra was reclassified as aBarosaurus vertebra, byMike Taylor andMatt Wedel.[21] However Brian Curtice has reassigned it toSupersaurus on the basis of additional specimens.[4]Michael Benton also agreed with the reclassification, giving theSupersaurus BYU 9024 specimen an approximate length of up to an impressive 50 metres (160 ft), which would have made it the longest animal to ever live.[22]
The assignment of the more complete specimen, WDC DMJ-021, toSupersaurus suggests that in most respects it was very similar in anatomy toApatosaurus but less robustly built with especially elongated cervical vertebrae, resulting in one of the longest-known sauropod necks.[11]
Most studies of diplodocid relationships have found it to contain two primary subgroups:Diplodocinae (containing those diplodocids more closely related toDiplodocus than toApatosaurus) andApatosaurinae (diplodocids more closely related toApatosaurus than toDiplodocus). Originally, it was thought thatSupersaurus was related to the long-necked diplodocidBarosaurus, and therefore a member of the subfamily Diplodocinae, however, with the assignment of the more complete WDC DMJ-021 most later studies foundSupersaurus to be a close relative of the familiarApatosaurus in the group Apatosaurinae.[11] However, some later studies cast doubt on this paradigm. One comprehensive study of diplodocoid relationships published by Whitlock in 2011 foundApatosaurus itself to lie at the base of the diplodocid family tree, and other "apatosaurines", includingSupersaurus, to be progressively more closely related toDiplodocus (making them diplodocines).[23]
In 2015, a specimen-levelphylogenetic study of diplodocids found thatDinheirosaurus lourinhanensis grouped withSupersaurus. The study considered that it should be a new species ofSupersaurus, in a new combinationS. lourinhanensis.[6]
