Back in 1942, scientists unearthed a striking new skull in Montana, in the US. It clearly belonged to a formidable predator, but was relatively small and slender compared to those of the ultimate predator king, T. rex. The team concluded that this was an adult from a new species, and eventually – after many decades of debate – the discovery was named Nanotyrannus. Over the coming years, several more possible examples were identified.