EARTH 7 Lecture Notes - Lecture 7: Archosaur, Background Extinction Rate, Basalt
Phanerozoic Marine Diversity Patterns
- Raup and Sepkoski, 1982
- A landmark study that first gave us an indication of significant, focused, extinction
events (arrows)
- Can’t be explained by typical background extinction
- Average species only live around 2 million years
- 99.999% of everything that has ever lived are extinct
The five great mass extinctions
- End permian 60% genera, 80% species
The end-permian mass extinction 250ma
- Earth’s most severe extinction event
- 80% of all marine species went extinct
- 70 of all terrestrial vertebrate species
- 10-30 million years for recovery of global diversity
What caused the end-permian extinction?
1. Formation of pangea
a. Severe decrease in the extent of shallow marine environments
b. New competition from invaders both on continental shelf and on continents
c. Lowering of sea level
d. Alteration of oceanic circulation and atmospheric weather patterns
e. Interior of continents much drier
i. Note: these would all be slow processes, with winners and losers
1. Can’t alone account for such a drastic extinction
2. When plate tectonics slow down, fewer volcanos and mountains in ocean
3. Volcanic eruptions
a. Siberian trap flood basalts 250ma
i. 3mil m\km3 of lava
ii. Enough to cover earth in 20ft of basalt!
b. Huge dust and ash clouds would have blocked sunlight
c. Released catastrophic amounts of co2 and so2 - global warming and acid rain
d. acidification/anoxia in the oceans
Synapsids (we are synapsids) were dominant at the end of the paleozoic
Many synapsid groups die out during the end-permian mass extinction
Archosaurs radiate early in the mesozoic. They dominate for almost the entire mesozoic (250-
65ma)
Why did archosaurs thrive while many synapsids went extinct?
1. Synapsids were dominant, but the entire ecosystem failed around them (all the rules
change during a mass extinction).
2. There’s reason to suspect that archosaurs were better adapted to arid environments
(which spread after pangaea formed).
find more resources at oneclass.com
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Document Summary
A landmark study that first gave us an indication of significant, focused, extinction events (arrows) Can"t be explained by typical background extinction. Average species only live around 2 million years. 99. 999% of everything that has ever lived are extinct. 80% of all marine species went extinct. 10-30 million years for recovery of global diversity. Enough to cover earth in 20ft of basalt: huge dust and ash clouds would have blocked sunlight, released catastrophic amounts of co2 and so2 - global warming and acid rain, acidification/anoxia in the oceans. Synapsids (we are synapsids) were dominant at the end of the paleozoic. Many synapsid groups die out during the end-permian mass extinction. They dominate for almost the entire mesozoic (250- Dinosaurs are a type of archosaur, evolve out of the group. Triassic mass extinction jurassic, dinosaurs and pterosaurs evolve. Dinosaur novelties: erect posture + narrow tracked gait.
