This argument works for the entire geologic column. The fossil record conforms beautifully to the principle of
faunal succession no matter where you're looking or what taxa you deal with. The fossil record is very very heavily sorted - science explains this by saying that it's sorted with respect to time, YECs have absolutely no explanation.
The research I'm doing for my dissertation is completely dependent on the reality of faunal succession. If all vertebrate animals who have ever lived all coexisted 6,000 years ago then the patterns I look at every day would not exist. You wouldn't see an orderly change from one fauna to another over time, it would be a giant jumbled mess.