Fossil Preservation
is very limited
250,000
= # of species of plants & animals in the fossil record
1,500,000
= # of known species of plants & animals inhabiting the Earth today
4,500,000
= proposed # of species of plants & animals inhabiting the Earth today,
taking into account species that have not yet been identified
Then consider ....
4,500,000 living species represents an “instant” in time; whereas
the fossil record covers BILLIONS OF YEARS.
FOSSILIZATION &
PRESERVATION BIAS
- What is a fossil?
- How to become a fossil
- Preservation processes
FOSSILIZATION &
PRESERVATION BIAS
- What is a fossil?
- How to become a fossil
- Preservation processes
What is a fossil?
The remains OR traces of pre-existing
life generally > 10,000 years old
BODY FOSSIL
TRACE FOSSIL
FOSSILIZATION &
PRESERVATION BIAS
- What is a fossil?
- How to become a fossil
- Preservation processes
How to become a fossil
1. Possess hard parts
“My only ambition in life is to become part of the fossil record.”
How to become a fossil
1. Possess hard parts
shell
bone
teeth
wood
[soft parts (rare)]
[traces]
Preservation processes
OR What happens next?
2. Rapid burial
FOSSILIZATION &
PRESERVATION BIAS
- What is a fossil?
- How to become a fossil
- Preservation processes
Preservation processes
1. Unaltered Body Parts
Preservation processes
2. Altered Body Parts
a. carbonization
b. permineralization
(petrifaction)
c. replacement
d. recrystallization
Preservation processes
2. Altered Body Parts
a. carbonization
- thin carbon film remnant
Preservation processes
2. Altered Body Parts
b. permineralization
(petrifaction)
-crystallization within pores
or openings
Preservation processes
2. Altered Body Parts
c. replacement
- original material is dissolved
& replaced by new precipitate
ex. chertification / silicification
ex. pyritization
Preservation processes
2. Altered Body Parts
a. carbonization
b. permineralization
(petrifaction)
c. replacement
d. recrystallization
Preservation processes
3. Molds or Casts
direct 'imprint'
infilled form
Preservation processes
3. Molds or Casts
(direct imprint)
(infilled form)
external mold
external cast
preserve ornate detail of surface patterns
Preservation processes
3. Molds or Casts
(direct imprint)
(infilled form)
internal
molds (& casts?)
3D
lose ornate detail of surface patterns
Preservation processes
3. Traces of activity
a. tracks & trails
b. burrows & boreholes
c. coprolites
d. gastroliths
e. artifacts
Preservation processes
3. Traces of activity
a. tracks & trails
impressions
of appendage
- on the surface
series of tracks
trails
track
trackway
Preservation processes
3. Traces of activity
b. burrows & boreholes
excavation into
SOFT sediment
burrows
- excavation
(digging in)
excavation into
HARD material
(rock or wood)
boreholes
Preservation processes
3. Traces of activity
c. coprolites !!!
- fossilized excrement
Preservation processes
3. Traces of activity
d. gastroliths
- stones ingested to aid digestion
smooth with tiny pitting on surface
Preservation processes
3. Traces of activity
e. human artifacts
- evidence of culture
But beware of…
Pseudofossils
“false fossils”
formed geologically through INORGANIC,
NOT ORGANIC processes
natural mineral
growth shapes
concretions