Dinos existed at least up to the time of (and a tiny number just after) the flood of Noah, which is why we are finding so many dinos with soft tissue still intact.
Yeeha!!! Saddle up and ride that T-Rex!
So why do you assume soft tissue could last 6,000 years, but not 18,000,000 years?
Once the specimen is sealed and the decay process stops, the length of time becomes irrelevant.
So have there ever been man and dino bones found in the same strata of earth?
I’m not poking fun by the way - just asking.