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Ultrasaurus
Ultrasaurus is the official name of a dinosaur exposed by Haang Mook Kim in South Korea, but the name was first old in 1979 by Jim Jensen to describe a set of giant dinosaur bones he exposed in the United States.
Mistaken assessments
The bones exposed by Jim Jensen, of Brigham Young University, at the Dry Mesa Quarry, Utah were originally believed to fit in to the largest dinosaur ever, so the name was widely used by the press and in scientific text.
Haang Mook Kim published a paper in 1983, telling a new dinosaur which he named Ultrasaurus tabriensis, because he supposed it was an equally giant relative of Jensen's dinosaur. However, Kim's assessment was wrong. His dinosaur was much smaller than he believed, because mistook a leg bone (femur) for an arm bone (humerus). But since Kim was the first to issue the name Ultrasaurus, the name officially applies to the South Korean dinosaur.
Jensen published a paper recitation his discovery in 1985, but since
the name Ultrasaurus was already in use (preoccupied), his discovery was
renamed in 1991 to Ultrasauros. However, Jensen also made a mistake. His
discovery was a chimera; the fossils belonged to two dissimilar dinosaurs,
both of which already had names. So his new name, Ultrasauros, is now
just an exchange name (junior synonym) for the dinosaur officially known
as Supersaurus.
Kim's Ultrasaurus is at present nomen dubium, which means not sufficient is known about the specimen to officially assign it to a specific family of sauropods. It may even be a member of a known genus or species, which would make the name Ultrasaurus a junior synonym as fine.
Description
Kim's Ultrasaurus lived 100 to 110 million years past, during the Aptian and Albian ages of the early Cretaceous. It is known from element of an upper forearm (humerus), and some back bones (vertebrae).
