Did an asteroid impact end the dinosaurs' reign? The controversy surrounding this question has been driven by a lack of dinosaur fossils dating to the period leading up to the impact in question. Now researchers show that a fossilized dinosaur horn found in Montana is from the relevant period, suggesting that dinosaurs were not extinct before the impact.

Tyler Lyson at Yale University in New Haven, Connecticut, and his colleagues found a 45-centimetre-long ceratopsian brow horn 13 cm below the Cretaceous–Tertiary boundary, a geological feature thought to mark the time of the extraterrestrial impact in what is now Mexico around 65 million years ago. They identified the boundary through analysis of nearby rocks and Cretaceous fossils. The horn is the youngest non-avian dinosaur fossil yet discovered.

Biol. Lett. doi:10.1098/rsbl.2011.0470 (2011)