Related knowledge: 1. Fossils include trilobites, plants, shells, footprints, dinosaurs and fish.
2. Formation conditions:
(1) Organic matter must have hard parts, such as shells, bones, teeth or woody tissues. However, even very fragile organisms, such as insects or jellyfish, can become fossils under very favorable conditions.
(2) living things must avoid being destroyed immediately after death. If the body parts of an organism are crushed, rotted or seriously degraded, it may change or cancel the possibility of this organism becoming a fossil.
(3) living things must be quickly buried by things that can hinder decomposition. The type of this buried material usually depends on the living environment of organisms.