Fossils: Formation and Classification

FOSSILS: FORMATION AND CLASSIFICATION

By: Mr. Marjonlien A. Mahusay

FOSSIL - the remnants or trace of ancient living organisms

that has been preserved in rock or sediment

Kinds of rocks containing fossil

1. Sedimentary rocks

2. Volcanic ash deposits

Fossilization- process of forming a fossil

Kinds of fossils

2. Fossils preserved in an amber or tar

1. Frozen or dried bodies

3. Preserved or replaced bones, teeth and shells

4. Petrified (premineralized) organisms

Turn into stone

5. Mold and cast

6. Carbonized impressions

7. Trace fossils

Fossil preservation

1.Death in an anoxic (oxygen free) environment

2. Rapid burial

3. Presence of hard parts

Classifying fossils

• according to its morphology alone

Naming:• Compared fossil forms from known organisms

Ex. Fossil organize with spiral shell that does not contain internal chamber is classified as a member of class gastropoda

Trilobites- 3 segmented shell that is divided across its width into 3 parts (arthropod)

Gastropods (snails)- spiral shell, does not contain internal chamber

Bivalves (clams & oysters) – shells that can be divide into 2 similar halves

Common invertebrate fossil

Brachiopods – resemble screen like grid of cells

Crinoides – looks like a flower, stalks consist of numerous circular plates stacked on top of each other

Grapholites – tiny carbon saw blades in a rock

Ammonites – spiral straight shell that contains internal chambers and has ridge surface

Corals

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