The evidence provided by the fossils means that Trilobites became extinct 252 million years ago and lived on Earth more than 521 million years ago.
Basically, a fossil is a remains which gives geologist information about the organism which lived in the past because when those organism dies, they decay and remain on or in the earth surface
Since the trilobite fossils are found in rock that are 521 million years and 252 million years old, then, it means that:
Trilobites became extinct 252 million years ago therefore, no other remains keep existing on rocks earlier.
Trilobites lived on Earth more than 521 million years ago
