Not all former life was preserved as fossils, in fact the vast majority simply vanished without trace. The most likely materials to survive fossilisation are the hard parts such as shells and objects which in life were constructed from resistant materials, such as Coral. In order for softer materials to survive, the conditions must be extremely favourable.
Fossils come in a variety of sizes, from minute traces to large skeletons. Trace fossils are clues to former life, they result from the activities or presence of creatures and plants. Examples of these traces include footprints, burrows and root tunnels. At the larger end of the scale, fossils also include bones, the largest of which belong to the dinosaurs, which existed between the Triassic and Cretaceous periods.
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