boreal means in the northern hemisphere. so it means that the meteor that killed the dinosaurs hit the earth when it was spring in north america. Different spe

boreal means in the northern hemisphere. so it means that the meteor that killed the dinosaurs hit the earth when it was spring in north america. Different species are more or less vulnerable in each season. Species that were hibernating at this time had a better chance of survival and in general species in the southern hemisphere did better because it was fall there and it was a less critical time for most species.