Got your wires crossed here. The Permian extinction line was 250mya and 20 millions years before the first dinos appeared. It destroyed the trilobites though, along with 90% of all species known at the time.<quoted text>
You wont find a single dinosaur fossil above the Permian Triassic extinction line . You may find places where the crust has been moved and there is no extinction line, or even places where layers are upside down. But it doesn't change the fact all dinosaurs were from before the Permian Triassic extinction line.
Which was 65 million ya, and all modern mammals, including hominids and humans will be above this line.
You are thinking of the Cretaceous extinction, the KY boundary, of 65mya. A milder event, but enough to put an end to the dinos.