What is the evidence given by scientistic to support that an asteroid caused mass extinction of plant and animal life?

A huge crater off the Yucatan peninula, I believe. Take it for what it's worth. This crater, they claim, dates to 65 million years ago and is large enough to have been caused my an extinction-level event asteroid.

The main evidence actually comes from the fossil record, rather than the crater.

See Cretaceous–Tertiary extinction event - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Cretaceous%E2%80%93Tertiary_extinction_event#Evide nce)

Another piece of evidence is the iridium layer all over the world that dates to the time of the impact. Iridium is a heavy metallic element not common on Earth but it is common in asteroids. Below the iridium leayer, dinosaur bones are common. Above it, they are not.