Charles Darwin devoted two chapters of The Origin of Species to fossils, but spent the whole of the first in saying how imperfect the geological record of life is. It seemed obvious to him that, if his theory of evolution is correct, fossils ought to provide incontrovertible proof of it, because each stratum should contain links between the species of earlier and later strata, and if sufficient fossils were collected, it would be possible to arrange them in ancestor descendent sequences and so build up a precise picture of the course of evolution.
This was not so in Darwin’s time, and today, after more than another hundred years of assiduous fossil collecting, the picture still has extensive gaps. Evolution (1999) p.106
There are still great gaps in the fossil record. Most of the major groups of animals (phyla) appear fully fledged in the early Cambrian rocks, and we know of no fossil forms linking them. Evolution (1999) p.109