Comment by wang_li

There's a strong case to be made that the impact not only was enough to trigger the extinction, it happened in 1 day. The theory is that the ejecta from the impact was voluminous enough that it was sent into space and then spread around the Earth. On reentry it heated the atmosphere to thousands of degrees. So animals in New Zealand that likely didn't even feel the impact died when the air was too hot to breath. The only survivors were things in burrows or nests or under water.