A newly discovered dinosaur that would one day give rise to the fearsome Tyrannosaurus rex has been given a suitably ominous name.
Moros intrepidus - the first part of which translates to 'the embodiment of impending doom' - roamed what is now Utah about 10 or 15 million years before T rex, palaeontologists say.
Its bones were found at a dig site known as the Cliffs of Insanity.
While Moros couldn't tower over its prey - it was about the size of a small deer - that didn't make it any less ferocious than its famous descendant.
"Moros was lightweight and exceptionally fast," said Lindsay Zanno, palaeontologist at North Carolina State University. "It could easily have run down prey while avoiding confrontation with the top predators of the day."
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Primitive tyrannosaur species emerged 150 million years ago, but it's long been a mystery how they evolved into T rex, which strode across the Earth in the dinosaurs' final days.
Moros fills a part of that gap.
"Although the earliest Cretaceous tyrannosaurs were small, their predatory specialisations meant that they were primed to take advantage of new opportunities when warming temperatures, rising sea-level and shrinking ranges restructured ecosystems at the beginning of the late Cretaceous," Prof Zanno said. "We now know it took them less than 15 million years to rise to power."
Then the asteroid hit, wiping out the dinosaurs. Some of the survivors ultimately evolved into today's birds.
The study was published in journal Communications Biology.