Trilobites Trilobites were crab-like animals
that lived in ancient seas.
Scientists have discovered many
trilobite fossils all over the world.
However, the fossils only appear
in rocks that are at least 250
million years old. In more recent
rocks, their fossils are absent.
1. What conclusion would you
draw about trilobites based on
their appearance and
disappearance in the fossil
record