A horn from one of the last surviving dinosaurs could finally prove that a massive meteor strike ended the reptiles' reign on Earth.
The 45cm-long fossilised browhorn belonged to a family of plant-eating dinosaurs that included the famous three-horned Triceratops.
It was found at a geological site known as the Hell Creek Formation in the bleak badlands of south-east Montana, U.S., where many other dinosaur fossils have been unearthed.
Reign: How a Triceratops might have roamed the planet. A horn from one of the crreatures has been discovered in south-east Montana, U.S.
What made this find so remarkable was its location, just 13cm below the rock layer that marks the Cretaceous-Tertiary or 'K-T' boundary - the point in the fossil record where the dinosaurs died.
This suggests dinosaurs were around right up to the time all traces of their existence vanished.
Scientist believe they then disappeared suddenly after an abrupt global disaster rather than a slow extinction.
- Sea monsters really DO lurk beneath the waves, scientists claim
- Shell on earth: How turtles survived the meteor impact that wiped out the dinosaurs
A huge asteroid or comet smashing into the Earth off the coast of Mexico at the end of the Cretaceous Period 65 million years ago is widely believed to have killed off the dinosaurs.
But some sceptics have repeatedly pointed to an absence of dinosaur fossils for three million years leading up to the impact as evidence that the creatures may have already gone when the meteor struck.
There has been an apparent lack of fossils buried within the 10 feet of rock below the K-T boundary. The area has become known as the 'three-meter gap.'
Impact: Scientists believe the fossil points to an asteroid hitting Earth 65million years ago