The scientific method can only disprove theories or increase the power of previous predictions that have yet to be disproved, but it can never absolutely prove anything to be absolutely true.
Therefore, the best thing to do in science is to continually question and test previous hypothesis and theories to see if they continue to hold up under scrutiny.
Some habitats are clearly more susceptible to the preservation of fossils.
If those specific habitats are not occupied by a particular kind of creature, it may not be preserved in the fossil record even though it is still alive and well in some other habitat.
This pattern arises when species that appear on few islands occur only on the islands with the most species, while only the most widespread species are found on the islands with few species (Wright et al., 1998).
The nested subset pattern arises because species differ in their distributions across space.
For most scientists all of this seems so obvious that it is difficult to question.
General mobility, ability to survive catastrophic conditions, and other ecological/habitat factors could also reasonably contribute to the differential location of trilobites vs. For example, coelacanth fish exist in the fossil record for what are thought to have been 400 million years.Since each of these layers seems so specialized it is easy to conclude that one type of creature gave rise to the next type of creature over the course of whatever time it took to form the various layers between them.