1. The fossil record 2

2. The fossil record 2 What is a fossil? Where do we find fossils?
Why study fossils?
Palaeobiology
Geochronology
Palaeoenvironments/climates
How are fossils formed?
Types of fossil preservation
Quality of the fossil record

3. Taphonomy - ‘fossilization’
The manner and cause of death
Processes of decay and decomposition
Transportation of fossils/potential fossils
Burial of remains
Diagenesis of remains

4. NB text-book, p. 8-17

5. Taphonomic information
life position, clustering
articulation, breakage, sorting, orientation
population structure - age and size frequency
trace fossils
sedimentology

6. Types of preservation ‘Unaltered’ remains Altered remains Imprints
Soft parts - very rare
Freezing
Mummification
amber, etc.
Hard parts
Altered remains
Petrifaction
Permineralization
Recrystallization
Replacement
Carbonization
Imprints
Moulds/casts
impressions
Tracks, trails and burrows

7. Unaltered remains - freezing
1999

8. Unaltered remains - freezing
Lyuba (age 4 months, 40kya old) - discovered in 2007 in Siberian permafrost

9. Unaltered remains - freezing
Dima (age 7 months, 40kya old) - discovered in 1977 by gold diggers in a lump of ice near the Kirgilyakh Creek

10. Unaltered remains - amber
Oligocene (~30Ma) amber, Baltic

11. Unaltered remains - amber
Oligocene (~30Ma) amber, Baltic

12. Altered remains - permineralization
Triassic (~230 Ma) trees, Petrified Forest NP, Arizona

13. Altered remains - recrystallization
NB. mineralogy is unchanged
gastropod/snail

14. Altered remains - replacement, e.g. aragonite to calcite
Peronoceras fibulatum
Placenticeras meeki
ammonites

15. Altered remains - replacement, e.g. aragonite to pyrite
Jurassic ( Ma) ammonites

16. Altered remains - carbonization
fossil fern frond (Neuropteris)

17. Imprints - moulds and casts
internal mould
external mould
imprints

18. Chemical/molecular fossils
degree of alteration may be difficult to determine

19. Quality of the fossil record
Chances of fossilization
Soft parts vs. hard parts
Lagerstätten
Biases
Sedimentary environment
e.g. marine vs. continental
Stratigraphic bias
older rocks - less exposure, tectonized
Collection
bias towards commonest and most accessible sedimentary facies (~environments)
NB. oldest ocean crust 165 m.y.

20. Chances of fossilization
~60% of marine animals are soft bodied and usually unrepresented in the fossil record (NB shell and coral carbonate is also broken down by bioerosions - up to 60% in coral reef settings)
Discalioides jellyfish, Oligocene, Provence, Southern France

21. Chances of fossilization
marine vs. continental environments + scavengers, decomposition

22. Lagerstätten deposits of exceptional value - conservation
- concentration
Solnhofen (Jurassic, S Germany) - a conservation lagerstätte
Shrimp - Aeger tipularius

23. Lagerstätten
Solnhofen (Jurassic, S Germany)
Dragonfly - Libellulium

24. Lagerstätten
Solnhofen (Jurassic, S Germany)

25. Lagerstätten
Messel (Eocene, Germany)
beetle

26. Lagerstätten
Messel (Eocene, Germany)
snake

27. Lagerstätten
Messel (Eocene, Germany)
Fish - Cyclurus kehreri

28. Lagerstätten Messel (Eocene, Germany)
Turtle - Allaeochelys crassesculptata

29. Lagerstätten Messel (Eocene, Germany)
Mammal - Propalaeotherium parvulum
Messel (Eocene, Germany)

30. Lagerstätten
Messel (Eocene, Germany)
Marsupial - Leptictidium nasutum

31. Lagerstätten
Messel (Eocene, Germany)
Bat - Archaeonycteris trigonodon

32. Lagerstätten Holzmaden (Jurassic, Germany)
marine reptile - ichthyosaur
Holzmaden (Jurassic, Germany)

33. Quality of the fossil record
Chances of fossilization
Soft parts vs. hard parts
Lagerstätten
Biases
Sedimentary environment
e.g. marine vs. continental
Stratigraphic bias
older rocks - less exposure, tectonized
Collection
bias towards commonest and most accessible sedimentary facies
oldest ocean crust 165 m.y.
UP TO HERE!!

34. Stratigraphic bias

35. Collection bias
e.g. oceans vs. shelf sediments
Europe vs. Asia, etc.

36. Quality of the fossil record - biases but ……

37. Quality of the fossil record
Palaeobiology and the Fossil Record Benton & Harper

38. Quality of the fossil record
‘corrected’ for sampling biases
Sepkoski data
PBDB data
Alroy et al. 2008, Science