Trilobites are animals that lived in the sea. Complete the sentences about how the fossils of trilobites A and B were formed.
The animal dies and falls to the sea bed.
The animal is buried in __________.

The first step in fossilisation is the rapid burial of the dead organism. This is crucial because it protects the remains from scavengers and from the oxygen that would cause rapid decay. At the bottom of the sea, the organism would be covered by layers of sediment, which is material like sand, silt, and mud that settles out of the water.