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Fossils
What is a fossil?
• A fossil is the preserved remains of a once-living organism.
A fossil may be:
• an original skeleton or shell;
• a mold or cast;• material that has
replaced the once living thing;
• traces such as footprints or worm tubes
What are the fossil types?
• Body fossils – actual parts of an organism, unaltered or altered
bones, shells, leaf imprints
• Trace fossils – evidence of life that is not a body fossil
tracks, burrows, casts
Body fossils
Trace Fossils
More on trace fossils
• Tracks – impressions of passage of living things
Fossil
records
document
the course
of life through
time
Fossil Evidence of Evolution
9
• Fossils document evolutionary transition• The oldest known bird fossil is the Archaeopteryx
• It is intermediate between bird and dinosaur
• Possesses some ancestral traits and some traits of present day birds
• Archaeopteryx was first found in 1859
Fossil Evidence of Evolution
10
Fossil of Archaeopteryx
Fossil Evidence of Evolution
11
Recent discoveries–Four-legged aquatic mammal
• Important link in the evolution of whales and dolphins from land-dwelling, hoofed ancestors
–Fossil snake with legs–Tiktaalik: a species that bridged the gap
between fish and the first amphibian
Fossil Evidence of Evolution
12Whale “missing links”
Fossil Evidence of Evolution
13
Homology of the bones of the forelimb of mammals
Anatomical Evidence for Evolution