Ultrasaurus is a genus of dinosaur that lived around 100 to 110 million years ago during the Early Cretaceous period. It was discovered in South Korea by a researcher named Haang Mook Kim.
The name “Ultrasaurus” means “ultra lizard.” Although it was first used informally in 1979 by another scientist, Jim Jensen, who found some large dinosaur bones in the United States, Kim was the first to officially publish the name in 1983 for his dinosaur.
When Kim described Ultrasaurus tabriensis, he thought it was a huge dinosaur, even bigger than another known dinosaur called Supersaurus. However, he made a mistake. His dinosaur was actually much smaller than he thought because he confused some of its bones.
Jim Jensen later published a description of his bones in 1985 but could not use the name Ultrasaurus anymore since it was already used by Kim. Instead, he renamed his findings to Ultrasauros in 1991. Unfortunately, it turned out that Jensen’s discovery was not from a single dinosaur species but from two different ones. Now, Ultrasauros is considered just another name for Supersaurus.
Currently, Ultrasaurus is considered “nomen dubium.” This means that scientists do not have enough information about its fossils to assign it to a specific group of dinosaurs.
So, Ultrasaurus gives us an interesting story about how names in science can change and how important accurate descriptions of fossils are.