<P> Ages show that the two volcanic phase hypotheses are well supported and the weighted mean ages of each volcanic phase are 376.7 ± 3.4 and 364.4 ± 3.4 Ma or 373.4 ± 2.1 and 363.2 ± 2.0 Ma, which the first volcanic phase is in agreement with the age of 372.2 ± 3.2 Ma proposed for the Kellwasser event . However, the second volcanic phase is slightly older than Hangenberg event which place at 358.9 ± 1.2 Ma . Viluy magmatism may have injected enough CO and SO into the atmosphere to have generated a destabilised greenhouse and ecosystem, causing rapid global cooling, sea - level falls and marine anoxia occur during Kellwasser black shale deposition . </P> <P> Other mechanisms put forward to explain the extinctions include tectonic - driven climate change, sea - level change, and oceanic overturning . These have all been discounted because they are unable to explain the duration, selectivity, and periodicity of the extinctions . </P>

What animals became extinct in the devonian period