1. The Cambrian fauna
1. Sepkoski’s Curves
2. The Cambrian fauna
3. Small shelly fossils
4. Archaeocyathids
5. Trilobites
6. Burgess Shale
7. Ecological overview

2. An analysis of shallow marine diversity through time
1. Sepkoski’s Curves
An analysis of shallow marine
diversity through time
Family diversity
Cambrian fauna
Ordovician radiation
End Permian extinction
Diversity = evolution - extinction

3. 2. Cambrian fauna Mud-eating trilobites and hyolithids
Simple brachiopods
Low tiering above
or below sea floor

4. Include diverse shapes and compositions
3. Small shelly fossils Ma
510
Include diverse shapes and compositions
Sometimes whole shells,
eg primitive molluscs
Sometimes parts of larger, cataphract organisms,
eg Wiwaxia
520
530
540
Cambrian
Precambrian
550

5. Cup-like forms, usually about 10 cm in height
4. Archaeocyathids Ma
510
Intervallum
Pore-bearing
outer wall
Inner
wall
520
Sole
Cup-like forms, usually about 10 cm in height
Could be solitary or colonial
Probably sponges
Calcareous skeleton
Filter feeders
530
540
Cambrian
Precambrian
550

6. 5. Trilobites Arthropods with diverse habits and modes of life
Highly developed senses and head
Trilobite diversity
through time
Segmented body and tail
Cephalon

7. 6. Burgess Shale Middle Cambrian Canadian Rockies
Preserved at base of a steep marine palaeoslope.
Most of fauna has been transported off a reef
Arthropods
dominate fauna
Abundant infauna
including predatory worms

8. 7. Ecological overview
1. Cambrian sees massive increase in diversity due to introduction of hard parts
2. Diversity plateaus at about 100 families
3. Dominated by mud-grubbers and food chains based on them
4. Low faunal tiering may have inhibited diversity, but archaeocyathids were reef builders
5. Faunal interpretations based on Burgess Shale suggest greater complexity.
6. Declined gradually though Ordovician and were badly affected by end Ordovician mass extinction