Fossil

From the Simple English Wikipedia, the free encyclopedia that anyone can change

A fossil is the remains, residue or trace of something that was once alive, but is now long-gone and dead. Very often, it is an imprint or impression in sedimentary rock of some animal, plant or protist that lived millions of years ago.

The most-common fossils are those left behind by the hard, calcitic shells of mollusks (such as clams and snails) and of now-rare brachiopods (also known as lampshells). These sea-dwelling shellfish have produced many fossiliferous (that is, fossil-bearing), chalky layers of limestone in the earth.

But the best-known fossils are those of the giant, prehistoric dinosaurs. The fossilized bones and fossilized footprints of these huge, ancient reptiles can be seen in many museums of natural history and earth science.

The study of fossils by geologists is known as "Paleontology"; while the study of fossils by scientists trained in biology is known as "Paleobiology." Likewise, "Paleozoology" is the study of prehistoric animals; while "Paleobotany" is the study of prehistoric plants. The study of fossil microbes is known as "Micropaleobiology"; while the study of prehistoric humans is known as "Paleoanthropology."

[change] Types of fossils

Microscopic or very tiny fossils are called "microfossils;" while larger, macroscopic fossils -- such as those of seashells and dinosaurs -- are called "macrofossils." Natural stones which look like fossilized organisms, but are not fossils at all, are called "pseudofossils."

Indirect evidence of prehistoric life -- such as a worm's trail or a mammal's footprint -- is known as a "trace fossil." Fossilized excrement, feces or dung is known as a "coprolite." Chemical traces of prehistoric organisms is known as a "chemofossil." Indirect evidence of prehistoric people is known as an "artifact."

Fossilization under the ground usually produces an external, "fossil mold" of the dead organism. This earthen mold, in turn, may produce a stoney copy or rocklike replica of the deceased organism known as an internal, "fossil cast" or "steinkern."

Occasionally, however, a fossil can be produced as a result of dryness (dessication), freezing, or pine resin. Mummified mammals, wooly mammoths, and insect-filled amber are examples of these rarely-found fossils.

"Living fossils", however, are not really fossils at all. Instead, they are modern-day organisms which very closely resemble their prehistoric ancestors of many millions of years ago. The ginkgo tree and horseshoe crab are good examples.