The same would be true if a meteor killed the animals, their remains would be deposited in a single meteor layer like the K-T Boundary.
There is no such "kill" layer.
All dinos but one were long gone by the K-T Boundary and that one, a species of Hardasaur lived another 700,000 years past it.
The fossil record of the Permain shows a similar gradual extinction.
Foraminifera.