1. How do fossils form? Biological materials Conditions needed for preservation Types of preservation, types of fossils

2. Fossilization2 VertebrateCrustaceanMolluskPlant DNA Protein Collagen Cellulose Mineral boneMineral shellLignin Teeth Biological Materials

3. Fossilization3 Conditions required for fossilization 1. Retard decay and chemical and physical breakdown 2. Burial 3. Fixation

4. Fossilization4 Step 1: Retard decay and chemical breakdown Anaerobic environment Reduces decay, but acidity may destroy DNA, proteins, and carbonate-bearing minerals Clay films Mg + Ca ++ Fe ++ C O-O- Carbonyl … first product of bacterial breakdown

5. Fossilization5 Step 2: Burial Removes object from destructive environment Paves entry to rock record

6. Fossilization6 Step 3: Fixation Reduces vulnerability to breakdown Drying or freezing Clay minerals fix organic material Minerals entering cells Mineral alteration - e.g. aragonite to calcite or dolomite

7. Fossilization7 Kinds of Fossils Unaltered remains Altered Hard Parts –Compression –Permineralization –Recrystallization –Replacement Traces –Impression –Mold-Cast –Tracks, trails, and burrows –Coprolites - that’s fossil poop, by the way Molecular fossils

8. Fossilization8 Unaltered Remains Original tissues preserved intact –Drying, freezing, or preservation in amber

9. Fossilization9 2D remains of 3D material Retain organic material Compressions

10. Fossilization10 Mineral infilling of porous spaces in skeletal elements like wood, bone, and echinoderm plates Can preserve cellular detail Permineralization

11. Fossilization11 Recrystallization Loss or blurring of original shell structure as shell is converted to interlocking crystals.

12. Fossilization12 Replacement Original material dissolved away and replaced by another mineral Pyritization, Silicification, Calicification, others

13. Fossilization13 2-dimensional imprints without any organic material Impressions

14. Fossilization14 Mold / Cast Physical characteristics of organisms are impressed onto rocks, especially coarse porous rocks like sandstones.

15. Fossilization15 Tracks Trails Burrows Other evidence that organisms were present Only evidence for behavior Ichnofossils

16. Fossilization16 Coprolites Fossil Excrement Extremely informative - what were they eating?

17. Fossilization17 Molecular fossils Chlorophyll Flavinoids Collagen DNA Lipids Proteins And their biochemical breakdown projects