1. Ordovician
The first vertebrates - jawless fishes called ostracoderms

2. Ordovician
Reef-forming corals called rugose corals

3. Ordovician
Eurypterids or sea scorpions - up to 2 m long

4. Ordovician
Major radiation of trilobites and brachiopods

5. Ordovician mass extinction
Occurred at the end of the Ordovician
Second largest mass extinction, especially for marine animals
Apparently caused by movements of southern continents toward the South Pole
Cooler climate caused more tropical species to go extinct
Water tied up in glaciers caused sea level to fall

6. Silurian
First land animals (millipedes, centipedes, arachnids)

7. Silurian
First jawed fishes (placoderms)

8. Silurian Appearance of first higher plant, Cooksonia
This plant had neither leaves nor roots
Its stem projected 10 cm high from which spores were released for dispersal

9. Devonian
First insects (both winged and wingless species)

10. Devonian
First trees and first forests

11. Devonian Explosive radiation of modern fishes
Associated with extinction of many jawless fishes
Two major groups
Ray-finned fishes (Actinopterygii)
Lobe-finned fishes (Sarcopterygii)
The pectoral and pelvic fins of the lobe-finned fishes had fleshy central portions unlike the ray-finned fishes

12. Devonian
First sharks

13. Ray-finned fish

14. Coelacanths

15. Coelacanth distribution

16. Lungfishes

18. How to make a leg out of a fin
A sarcopterygian fin is made up of preaxial, axial and postaxial elements
To make a leg of a fin, the axis of the limb has to curve around
Some of the preaxials were incorporated into arm and wrist
The postaxials end up as the digits

19. Acanthostega - amphibian but probably fully aquatic

20. Devonian
First land amphibians (Ichthyostega)

21. Devonian mass extinction
At end of Devonian
Primarily affected marine organisms
Rugosan corals, brachiopods, trilobites, jawless fishes and placoderms greatly affected
About 60% of existing species went extinct
What was the cause?
Most species affected were warm water forms, suggesting that global cooling might have been responsible

22. Carboniferous
Climate was warm and humid
Extensive coal-forming swamps

23. Carboniferous Dragonflies with 70 cm wing spans (Meganeura)
Millipedes over 2 m long

24. Carboniferous Extensive radiation of amphibians Bewildering diversity
Two groups evolved of great importance
Lissamphibia - gave rise to living amphibians
Anthracosaurs - gave rise to reptiles, birds and mammals

25. Anthracosaurs

26. Carboniferous
First reptiles (amniotic or cleidoic egg)