Edward Drinker Cope found the pieces of backbone in 1892, which he named “Manospondylus”. He believed they belonged to a ceratopsian dinosaur like Triceratops originally. These remains would later be shown to belong to T. rex. However, it was not until Barnum Brown found partial skeletons in 1900 and 1902 that a better picture of what this dinosaur actually looked like.
It was Henry Fairfield Osborn who would ultimately name one of the skeletons Tyrannosaurus rex, meaning “King of the Tyrant Lizards” in 1905.He named the other skeleton “Dynamosaurus”, but later realized they belonged to the same species of dinosaur, and decided to keep the name Tyrannosaurus.
These two skeletons would be all that was known of Tyrannosaurus until the 1960s, when 42 different skeletons were uncovered, some of which were mostly complete. Further discoveries continued into the 1990s, when two of the most complete T. rex skeletons ever were discovered, which were nicknamed Sue and Stan.
In 2001, a smaller T. rex-like skeleton was discovered and named Nanotyrannus (“Pygmy Tyrant”), though most paleontologists now agree that it represents a juvenile T. rex. Since then, other small skeletons have been discovered, which help give a better picture of what a young T. rex looked like.
In 2022, paleontologist Gregory S. Paul and others released a paper stating their belief that Tyrannosaurus rex was actually three separate species: T. imperator, T. regina, and T. rex. They cited differences in body proportions and number of teeth, among other features, as evidence of this separation. Other paleontologists have criticized this study, though some do concede that it’s likely there are more species of Tyrannosaurus than just T.rex.