End Permian Extinction on Land (studied in Karoo deposits, S. Africa): :

1. Reptiles (ancestors Dinosaurs, ancestors mammals, amphibians: rapid extinction
2. Plants: gradual replacement of scale-tree floras by conifers, cycads (from middle Permian on), no rapid mass extinction
3. Short-term ecological disturbance (Karoo: river patterns change; 'fungal spike'). Plants show major disruption of life: dense vegetation, meandering rivers before extinction, scarce vegetation, braided rivers after.
4. Insects: gradual extinctions since middle Permian (all giant insects extinct)

One continent: could have influenced global diversity

• Overall low diversity
• Large continent: interior has harsh climates (cold winters, hot summers)
• Large areas with high elevation (harsh climate)

BUT: continents became one BEFORE end Permian (in middle Permian), gradual process; remained one long AFTER extinction (until Early Jurassic).

• There was a prolonged period of higher-than-average rates of extinction (over several millions of years
• Topped of by an extinction of many species within a few hundred thousands of years, possibly even within a few ten thousands of year.

1. Trilobites
2. Paleozoic corals
3. Many crinoids (sea lilies; Echinodermata)
4. Many brachiopods
5. Many bryozoa
6. Many sponges

Extinction at end Permian: led into development of Mesozoic faunas, typically with more energy-intensive organisms (e.g., crawling/burrowing bivalves rather than brachiopoda).

Selectivity of P/T extinction in oceans: 

 Is there a pattern in these extinctions?

Most severely hit:

• Heavily calcified organisms (e.g., corals)
• Organisms with passive gas exchange (not active circulation, e.g., by gills), such as Brachiopods, Echinodermata (sea lilies), Bryozoans.
• Very high CO₂ levels (hypercapnia=CO₂-poisoning), disturb the acid-base balance of internal fluids.
• Evidence from sediments: in many locations in open ocean low oxygen conditions; affect organisms with slow circulation most

NOTE: Mechanism of extinction: must affect land and sea biota.

• High temperatures (less O₂ dissolves)
• CH₂O + O₂ -> H₂O + CO₂ : oxidation of organic matter (reverse of photosynthesis reaction!)
• Anoxia in oceans: maybe oceans first very sluggish (organic matter on bottom rots), then sudden overturn, gases come out?
• New theory: methane hydrates dissociate: CH₄ + 2O₂ -> CO₂ + 2H₂O (Note: methane, CH₄, is a greenhouse gas)

Methane hydrates: 10,000 Gigatons stored in sediments; permaforst soils at Arctic, deep-sea sediments (wherever there is organic matter, from which bacteria produce methane, and low temperatures and/or high pressures).

Methane hydrates: methane stored in ice, 'The ice that burns':

If oceans warm up by several degrees, hydrates melt, methane escapes into oceans, atmosphere; leaves chemical (carbon isotope) evidence in fossil record.

• Continents form one land mass  (One continent: may have been a factor of long-term decline in diversity, probably not main cause of rapid extinction)
• Global cooling (volcanoes): cooling was much earlier
• Global warming (volcanoes): Siberian traps
• Low oxygen conditions (oceans)
• Low sea level (not much area with shallow seas) : timing low sea level wrong, sea level was rising during extinction
• Impacts of meteorites or comets: possible, no crater of correct age found; various lines of evidence that there may have been an impact (chemical signature from fall out), but none unequivocal
• Supernova explosions: no evidence

Why warming? How did it cause extinction?

• Long-term warming (a few millions of years): CO₂ from Siberian flood basalts
• Long-term warming caused dissociation of methane hydrates -> more greenhouse effect, more warming -> more methane hydrate dissociation, etc. (positive feedback effects)
• Methane oxidation causes anoxia and CO₂-poisoning in oceans
• Land: poisoning volcanic fumes, changes in climate
• Impact may have complicated matters..

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