We were able to observe on that one ranch that the whole world had changed dramatically! We found dinosaur bones in the terrestrial Cretaceous Lance Formation on the first day. Then we saw a marine section of Cretaceous strata with marine ammonites in it at the first site on this ranch the second day. And then we could see that the world changed entirely when the meteorite impact catastrophically wiped out the dinosaurs. So that in the terrestrial layers laid down in the Tertiary all that dinosaurs were gone but the mammals now ruled! Some of them became very large, like the Titanothere.
The K-T Boundary was the end of the dinosaurs but the beginning for the mammals and the boundary between the Mesozoic and Cenozoic Eras.