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Fossil
any remains, impression, or trace of a living thing of a former geologic age
Tell us about past environment – can be used to date rocks
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Porifera
– sponges, spicules w/ distinctive spikes
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Protezoa
single cell eukanyote
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Cridaria
Corals, jellyfish, have radial symmetry
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Brachiopoda
lamp shells, left/right symmetry, shells not symm to each other
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Mollusca
clams, gastropods (slugs,snails) cephalopods
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Arthropoda
- Insects, crustaceans,
- Trilobites (early cambrian to late permian)
- segmented exoskeleton, bilateral symm.
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Echindermata
crinoids, sea urchins, sea star - 5 way radial symmetry
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Cordata
notochord, aka nerve cord, bilateral symmetry
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Required factors for fossilization
fast complete burial, anaerobic environment
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Unaltered Remains
encased in amber, bog people (anaerobiv env.), frozen
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Replacement
original biological tissues are replaced by new mineral
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Permineralization
(petrified wood) – fluids fx. dissolved quartz may precipitate though wood, filling in voids
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Carbonization
thin carbon film left behind after compression, can record detailed microstructure
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Mold & Cast
- internal and external casts- tracks, burrows, tunnels, footprints (trace) fossilized dung
- (copralites)
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