Dinoflagellates
Thousands of varieties and untold billions of individuals right up to the iridium clay marker, then total wipe out.
Every ocean on earth abruptly lost essentially all of its plankton in the blink of an eye.
This is a much clearer indication of a global disaster than the remains of a few thousand dinosaurs spread out over a 100+ million year's worth of layer after layer of sedimentary rock.
The "hardasaur" date that you cited was dated by the U-Pb technique. It measures the ratios of uranium and the decay product lead in the fossil. The uranium isn't in the animal's bones when it dies, but leaches in over time as part of the fossil mineralization process.
Usually this process is complete in a few thousand years.
Usually.
If the bones aren't exposed to liquid water the process of leaching minerals into the bones goes on hold. For how long? Until liquid water returns. In an Atacama type desert that could be millennia. Even in the presence of occasional rain the bones could be kept dry by overburden, nor is Dr Heaman immune to a 1% error in his dating technique.
Perhaps Dr Heaman is correct, perhaps a few pockets of undamaged land held some survivors and they were able to eek out a living for a while. That doesn't change the BIG picture of a mass extinction.
Or perhaps the test was skewed by modern uranium contamination? The fossils are from New Mexico, and a goodly fraction of the southwest was contaminated with fallout from hundreds of above ground A-Bomb tests and "venting" of below ground tests back when I was a kid.
More than one prospector thought they'd struck the mother load of uranium ore after those tests...