I have a theory: With the magnetic pole shift 65 000 000 years ago it could have caused extinction in this manner:
If a meteorite DID strike the earth couldn't the magnetic pole shift have attracted the metal in the meteorite thereby pulling it towards the earth with the resulting impact destroying the structural tissue of most animals at the time.
Meteors have mass and mass is effected by gravity and the gravitational pull of the earth is much greater than it's magnetic attraction. Even if the meteor that did strike the earth 65 milliom years ago was composed of pure iron, which is in no way certain, the force excerted by the magnetic field of earth is miniscule compared to its gravitational attraction on the mass of the meteor.
In reality both the meteor and earth were in orbit around the sun and the collison occured simply because their orbits crossed paths.
Additionally, it is my understanding that the magnetic pool reversals occur after the weakening of the magnetic field and that the extictions associated with the reversal would theoretically be caused when the magnetic field fails to provide the shielding affect of the magnetoshere and the earth is bombarded with high energy particles from the sun making life difficult on the surface of earth.