<em>Fossils are formed in many different ways, but most are formed when a living organism (such as a plant or animal) dies and is quickly buried by sediment (such as mud, sand or volcanic ash).</em>
Most animals become fossilized by being buried in sediment. For them to be fossilized, they have to be buried and leave an imprint before they decompose. Animals without skeletons are seldom fossilized, because they decompose so quickly. Animals with hard skeletons are much easier to fossilize.
