1. The Paleozoic

2. Cambrian Period MYA
Named by Adam Sedgewick as a Latinized form of Welsh name for Wales (Cymru).
Period begins with the breakup of a supercontinent called Pannotia, centered on the south pole
Increase in the number of animals with hard exoskeletons. It likely began as a way to sequester Ca, but continued with larger body sizes following predation.
CO2 (~1.4%) O2 (rose to ~14%)

4. Ordovician Period 485-443 MYA
Named after a Celtic Welsh tribe by Charles Lapworth to resolve a fight between Sedgewick and Murchison
Transition from Cambrian marked by an extinction event
To Silurian by a more significant extinction event (~60% lost)
Continents remained southern in distribution

5. Silurian Period MYA
Roderick Murchison named this rock sequence after an ancient Celtic tribe of Wales
Continental masses equatorial and began to collide
Vascular plants appeared on land
Jawless fish continued to diversify and jaws appeared

6. Devonian Period MYA
Named after Devon, England by Murchison and Sedgewick
Vascular plants diversified
Vertebrates began to move onto land
End of the period marked by a series of extinctions

7. Carboniferous Period 358-298 MYA
Named for coal-bearing strata by William Conybeare and William Phillips
Mississippian ( MYA)
Pennsylvanian ( MYA)
Southern continents (Gondwana) were centered over the south pole generating a southern hemispheric ice age
Romer’s Gap ( MYA) caused by mass extinction and drop in oxygen
Rise in importance of ray-finned fishes and crinoids
Gradual rise in oxygen to 35% as more carbon sequestered
Rise in terrestrial arthropods, amphibians and reptiles
Toward the end of period (~305 MYA) rainforest collapse –a minor extinction event

8. Permian Period MYA
Named for the city of Per’m in the Russian Ural Mountains by Roderick Murchison
Assembly of Pangaea with large continental desert
Modern terrestrial vertebrate groups became dominant
Largest extinction event of the Phanerozoic at end of the Permian –most life extinguished

9. Causes of the end Permian extinction
Volcanism
Methane hydrate release
Anoxia
Hydrogen sulfide release
Influence of Pangaea