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1

Trace fossils

Tracks burrows and borings. Behavioural activitys of extinct organisms

2

Why should we study fossils?

Bio stratigraphy, palaeography, paleoecology, simple fascination, evolution

3

Taphonomy

Study of how living organisms become fossilized

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Types of preservation processes

Per mineralization, unaltered remains, carbonization, dissolution and replacement, recrystallization

5

Per mineralization

Many bio tissues are full of pores and canals, these decay and the fossil gets buried, and the pores are permeated with flowing groundwater and gone minerals within the groundwater. New minerals fill the pores, and none of the original material is removed

6

Recrystallization

Some shells are made of unstable minerals that revert back to calcite after burial. Shape stays the same and so does the chemical comp, but there is a difference in texture

7

Replacement

Original shell may be dissolved due to water circulation. This is then replaced without leaving a void, and a new mineral precipitates

8

Carbonization

Fossil is preserved as thin lines of carbon on the bedding planes of sandstones and shales- outlines details of the organism

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Body fossils

Most fossils are hard parts of organisms

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Factors affecting fossilization potential

Biological agents, mechanical agents, diagenesis

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Biological agents

Predators and scavengers are active in breaking up shells and bones

12

Mechanical agents

Wind waves and currents. Shape density and thickness are important factors

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Diagenesis

After burial Diagenetic changes can easily destroy shells

14

Tectonic deformation

As muds containing shells are compressed under lithification, the fossils that are formed can start to deform, making identification more difficult

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Exceptional preservation

Lagerstatten. An abundant amount of fossils

16

Obrution deposits

Resulting from the episodic smothering of sea floor that strongly reflects benthic biotas

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Stagnation deposits

Formed under anoxic conditions that allow delicate preservation of body fossils

18

Burgess Shale

Mid Cambrian Rocky Mountains of bc

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Why is the Burgess Shale so important

Gives us a snapshot into the Cambrian explosion
Question of origins: how did so much anantomical variety evolve so quickly?
Question of consequences: introduced a number of architectural designs that were unknown to us

20

Chengjiang

Lower Cambrian
China
Arthropods
Soft bodied preservation

21

William lake

Upper ordivician
William lake Manitoba
Jellyfish
High salinity

22

Solnhoffen limestone

Upper Jurassic
Germany
Crustaceans, invertebrates, fine grained limestone

23

Messel

Middle Eocene
Germany
Plants insects invertebrates

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Temporal trends in lagerstatten distribution

Concentrations in time correspond to particular environments

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Process related vs pattern based

Process: rely on the knowledge that gave rise to them
Pattern: distribution of characters

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Process related example

Biological species concept developed by gg Simpson but Ernst was a supporter
A species is an array of organisms that are actually or potentially interbreeding

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Problem with the process related example

Problem with it is that few organisms have been observed and their breeding behaviour observed
Also fossils don't usually show breeding
It is doe sexually producing organisms not asexually

28

Pattern based example

Morphospecie concept: a species is a diagnosable cluster of individuals in which there is a pattern of ancestry and descent and beyond which there is not

29

Ontogenic variation

Changes an organism goes through during its lifetime

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Accretion

Adding on of discrete growth layers onto exoskeleton