How do fossils provide a check on estimates derived from molecular biology?

Answer

They anchor molecular divergence dates in actual, verifiable geological time.

Molecular clocks estimate divergence times based on mutation rates; fossils provide the concrete historical confirmation by showing when the physical representatives of those divergent groups actually existed in the geological timeline.

How do fossils provide a check on estimates derived from molecular biology?
paleontologyevolutionfossiltheoryevidence