Answer:
The trilobite fossils are found in the bottom layer only because they are always attached to the sedimentary rocks as other marine organisms fossil.
Step-by-step explanation:
- Mostly all the fossils are formed in fossil layers in sedimentary rocks at the bottom of the sea.
- Trilobites were the exclusively marine arthropods those were found in the sea water ranging from shallow to deep sea water.
- The fossils of trilobites are mostly found in the rocks containing the fossils of other marine animals such as corals, brachiopod and crinoids.