Stegosaurus and Triceratops were not part of the same assemblage because they lived at different times.
Obviously, the fossil assemblages change from period to period.
For example, human beings and modern elephants are part of the same assemblage because we live in the same time period.Now, when we use fossils to date rocks, we have to be careful. Remember that some species of animals and plants lived for a very long time, while others existed only for a short period of time.We don't want to use fossils belonging to species that lived for too long; these fossils would show up in more than one rock layer.One outcrop shows layers from one geologic time period, while the other outcrop represents a different time. Can he put the pieces together to make the story more complete? Let's find out how scientists deal with this common problem by using the fossils inside the rocks.Back in 1793, there lived a land surveyor named William Smith.