Debate over what caused the sudden extinction of the dinosaurs has raged for decades, but the discovery of a fossilized horn in Montana has leant weight to the theory that a colossal asteroid impact was largely responsible.
Around 65 million years ago the age of the dinosaurs, which had lasted for over 100 million years, was brought to an abrupt end. While the asteroid collision hypothesis has been regarded as highly plausible, a vocal section of the scientific community has pointed to inconsistencies in the fossil record which challenge this explanation.
Evidence for an asteroid catastrophe can be found in geological formations dating from 65 million years ago, known as the K-T boundary, which contain an abundance of iridium. Iridium is rare in the Earth’s crust but common in asteroids. However, dinosaur remains peter out of the fossil record below the K-T boundary, suggesting that dinosaurs may have gradually gone extinct for other reasons.
The new fossil unearthed by palaeontologists at Yale University has been found a mere 13cm below the K-T boundary, showing that dinosaurs were alive and kicking later than had previously been thought. “Here we have a specimen that basically goes right up to the boundary, indicating that at least some dinosaurs were doing fine,” says Tyler Lyson who led the team that made the discovery.
The horn, which comes from a dinosaur species similar to Triceratops, was found by chance while two members of the team were on a break. Not everyone is convinced by the finding though. Proponents of rival theories point to the rarity of fossils from the period closely preceding the asteroid collision, suggesting gradual extinction is still likely to have occurred.