At the end of the triassac something happened. Conditions changed in a way that favored the dinosaus over other groups. Other groups largely disappeared, and the dino took over. The dinosaurs were able to diversify which they'd previously been excluded from. And then their competitors, the cocadilians, can't survive the sudden temperature drops. They're just wiped out Tearelatively part of their time is left uninhabited by large vertebrates. In the next few million years we'll find out how these creatures survived on earth.