Fossils

2. fossil – a fossil of a species used to determine the relative age of rock layers.
8. – the hard outer covering of many organisms that is commonly preserved in the fossil record
9. fossil – a fossil formed when minerals replace the original organic material.
10. – fossilized tree resin that may preserve ancient plants or animals.
11. – the preserved remains, impression, or trace of a once-living organism found in rock.
12. fossil – evidence of an organism's activity, such as footprints, burrows, or trails.
14. – the process by which organic material is preserved as a thin film of carbon.
16. fossil – the preserved remains of an organism, such as bones, shells, or teeth.
17. – fossilized animal dung preserved in rock.
19. – a member of a group of extinct reptiles that lived during the Mesozoic Era.
20. – an extinct marine mollusc with a coiled shell, widely used as an index fossil.

1. – the natural process by which the remains or traces of organisms become fossils.
3. – the complete disappearance of a species from Earth.
4. – the hard framework of bones or cartilage that may be preserved as a fossil.
5. fossil – a hollow impression left in rock after an organism has dissolved.
6. – an extinct marine arthropod commonly found as a fossil.
7. – material that buries and protects organisms, allowing fossils to form.
13. fossil – a fossil formed when a mold is filled with minerals or sediment.
15. fossil – a fossil showing the imprint of an organism without preserving its original material.
18. – the study of ancient life through fossils.