“So, it seems on the cards that a species that was thought to be extinct a long time ago by fossil records may have become extinct much more recently than we thought.”
Well, that might be a possibility if the triceratops were found in strata that correspond to only a few thousand years ago (according to standard geologic interpretation), but that is not what we are looking at. We are looking at unfossilized cells from strata that geologists date at tens of millions of years old. The only possibilities are:
a) There is some unknown process that allows biological matter to survive without decaying for tens of millions of years
or
b) The standard interpretations of geologists and evolutionary biologists are wrong.
Those are really the only options.
It is indeed possible that some of these dating methods are not as reliable as they are argued to be. But seems to me there is only a conflict if the same samples appear to be young by tissue and old by strata, or if a young by tissue sample is so similar to an old by strata sample that it was not feasible they could be that far apart in history.
I will agree, that anomalous data should serve as a warning not to get too cocky when making nice neat little models about what happened in the past. But I am just saying there is no reason to expand such evidence to the nature of the universe all in a rush.