Discovering Fossils

Discovering Fossils — page 3
chapter WhAt ArE FOSSILS Fossils are the remains or traces of plants and animals These remains are preserved in rock Fossils can come from species that are still alive today Others are from extinct species such as dinosaurs Fossils can take several different forms Trace fossils are records of an organism’s activity They include footprints and nests Other fossils are the actual remains of a plant or animal These are called body fossils Often the remains of an organism decay over time But in some cases an impression of the organism stays in the rock This is called a mold fossil Sometimes minerals fill a mold fossil and crystalize inside it This forms a replica of the organism’s remains This replica is called a cast fossil Rock containing fossils is worn away by water and wind This erosion sometimes exposes fossils Paleontologists then uncover 1 6