In 2003, palaeontologists from the Burpee Museum of Natural History in Illinois unearthed a dinosaur they thought looked like a tiny cousin of Tyrannosaurus rex. Half the size of the notorious killer, they dubbed it Nanotyrannus.
But then some researchers began having doubts. What if Nanotyrannus was a juvenile T. rex?
After all, older specimens of many animals look very different from the young.
This was not the first fossil of a smaller Tyrannosaur that was found. Disagreement about its status had begun decades earlier.