It’s certainly possible, and I think even likely. It’s often the case that extinction events have multiple causes.

Presumably, if the bone’s location could be so easily explained away, it wouldn’t be making such a splash. These people do this for a living – it’s generally safe to assume that issues like this are well-resolved before anyone bases any major claims on them.

I do not see how Lyson et al can be so assured that their discovery proves the animal was alive so close to the KT boundary. I mean, can they exclude that the bone was near the surface because deposits above had been eroded away, the animal having been buried for several millions years? The animal could have been fossilized in river mud as mudstone which later was pushed up by seismic action and then the surface eroded back to leave the bone just below the new surface. It is geologically common, so cannot be excluded surely.

I am not defending the thesis that the dinosaurs were long dead when the asteroid fell, just questioning the assurance of the claim that this proves they were not.

The cataclysm supporters on the other hand, state that the entire ecosystem was doing just fine and that dinosaurs were thriving right up to the end and would have continued to dominate the landscape if the asteroid hadn’t hit. So in those terms, they ARE mutually exclusive. You can’t be thriving all the way to the end and declining at the same time.

On the other hand, you could be going through a temporary decline in fortunes, an ecological rough patch, from which, once you make it through, you rapidly recover your former levels of diversity and success and sustain them to the present day, if it were not for the unfortunate blow that knocks you over at your weakest point.