Ultrasauros is a name from the history of sauropod research, not a separate accepted dinosaur genus today. In the 1980s, material from the Dry Mesa Dinosaur Quarry in Colorado appeared to combine an enormous vertebra with an equally imposing shoulder girdle. Together, the bones suggested a sauropod of exceptional size. Reassessment showed that the key elements came from different animals and that the name-bearing vertebra belonged to Supersaurus.
The episode is a useful reminder that a quarry can preserve a rich assemblage without preserving every bone in anatomical connection. Large fossils found near one another may belong to different individuals or genera. A catalogue can retain Ultrasauros as a historical name, provided the card explains that it does not represent a distinct accepted species.
How the Dry Mesa quarry produced a giant
Field teams working at Dry Mesa recovered bones from numerous sauropods. Many were isolated or disarticulated, so researchers had to decide which elements belonged together. James Jensen described several enormous sauropod names from this material. His interpretation associated the dorsal vertebra BYU 9044 with a massive shoulder assembly, producing an animal that combined proportions later recognised in different sauropod lineages.
The mismatch was not visible from size alone. A vertebra can be compared by its articulations, neural arch and pneumatic spaces; a shoulder blade and coracoid carry their own diagnostic anatomy. When those elements are treated as one animal without adequate association, a reconstruction can combine traits that no individual possessed. The resulting body may be visually coherent while taxonomically mistaken.
Two names, then a replacement
Jensen initially published the name Ultrasaurus macintoshi in 1985. Because that genus name had already been used for a different animal, George Olshevsky proposed the replacement spelling Ultrasauros in 1991. The replacement resolved the naming problem; it did not establish that the fossil represented a distinct biological lineage.
The type of Ultrasauros is the large dorsal vertebra BYU 9044. The old reconstruction also relied on a large scapulocoracoid, including BYU 9462, which was later identified as belonging to a brachiosaurid. A replacement name follows the name-bearing type, not every element historically associated with it. That distinction is why the vertebra's reassignment determines the fate of Ultrasauros.
Why the type is referred to Supersaurus
Curtice and colleagues re-evaluated the sauropod assemblage and concluded that BYU 9044 belongs to Supersaurus vivianae. Its vertebral anatomy was consistent with a posterior dorsal vertebra of that diplodocid, rather than the anterior dorsal of a brachiosaurid assumed in the earlier reconstruction. The specimen's quarry context and anatomical comparisons supported the reassignment.
Under that interpretation, Ultrasauros is a junior subjective synonym of Supersaurus. “Subjective” means the synonymy is a taxonomic judgement based on comparing fossils; it is not an automatic rule of nomenclature. The bones remain real and scientifically useful. What disappears is the claim that they establish an additional accepted genus and species.
What can still be learned from the name?
Ultrasauros remains worth documenting because its history shows how quarry association, specimen numbering and changing identifications shape reconstructions of giant dinosaurs. It also illustrates why record counts must distinguish accepted taxa from historical names. This page retains the name for search and historical context; it does not count the animal as a separate biological species.
The English dinosaur catalogue includes an Ultrasauros card to match the Russian atlas, but its description identifies the name as historical and points to Supersaurus for the accepted animal. That lets readers find the old label without mistaking it for an additional sauropod. Other Morrison sauropods can be compared in the dinosaur catalogue, where each card should be read alongside the strength of its fossil evidence.
Frequently asked questions
Was Ultrasauros a separate species?
The name was proposed for material whose type vertebra is now referred to Supersaurus. It is generally treated as a junior subjective synonym, not a separate accepted species.
Why was the name changed from Ultrasaurus?
The earlier name was preoccupied by an already named genus, so Ultrasauros was proposed as a replacement spelling.
Which fossil is the type of Ultrasauros?
The name-bearing specimen is the dorsal vertebra BYU 9044. It is the element reassigned to Supersaurus.
Did the giant shoulder bones belong to the same animal?
No. The scapulocoracoid used in the old reconstruction belongs to a brachiosaurid, not to the individual represented by the Ultrasauros type vertebra.