The fossil, found in the famous Hell’s Creek formation in the US, could help to settle one of the longest running controversies in modern palaeontology – were the dinosaurs wiped out suddenly by a catastrophic impact, or did they die out gradually over many centuries?
Most scientists agree that the evidence points towards there being a huge asteroid impact on Earth at the end of the Cretaceous period, a time referred to as the ‘Cretaceous-Tertiary’ (K-T) boundary. However, palaeontologists disagree as to whether it was this catastrophic impact that killed off the dinosaurs, or whether they were killed off gradually thousands of years before the impact.
So far, advocates of the gradual extinction theory have pointed towards an area directly beneath the K-T boundary which lacks fossils as evidence for a gradual extinction – this is the so-called “three metre gap”. However, the new fossil – a horn fragment belonging to a ceratopsian dinosaur like Triceratops – was found just 13cm under the K-T boundary, which suggests that in fact there were dinosaurs alive much later than previously thought, and lending support to the idea that it was the asteroid which killed off the dinosaurs.
The researchers stress that although their work lends support to the asteroid extinction theory, there is still a considerable area devoid of fossils in this region, and more fieldwork and analysis is required to settle the question once and for all.