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The Devonian saw the first terrestrial trees, insects, predatory fish, and many warm tropical reefs. The length and nature of the late Devonian extinction is highly disputed, with estimated lengths between 25 Myr and 500k years. One estimated cause is ocean anoxia, due to eutrophication, due to runoff from a new layer of soil created by the deep root systems of new trees. The sedimentary record shows the oceans had a widespread anoxia problem, and had lots of continental soil there too.
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Massive, 96% of all marine, 57% of all families, and 83% of all genera. Life on the surface was mostly dog-like creatures living in conifer forests. We know of the extinction because, in Lootsberg pass, the fossil record before 252 mya shows a lot of variety, and after it homogenizes. In the Italian alps the sediment contains a lot of pollen until 252 mya, where it disappears. Scientists believe this extinction was caused by an increase in the acidity of rain, caused by volcanic eruptions.
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34% of all marine life, at least 50% of all species, and many large amphibians went extinct here. Mostly this vacated terrestrial niches, allowing dinosaurs to become dominant. The major theory is that the breakup of pangea caused enough volcanic activity to release enough CO2 to warm the climate past most species habitable limits. The Triassic was warm, and the massive distance between oceans and the center of the super continent allowed for extremely arid deserts.
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All non-avian dinosaurs died, along with 75% of all species. The commonly accepted theory is a massive comet or asteroid (10 km wide) impacted a peninsula in mexico. Two major evidences support this, the Chicxulub crater and a thin boundary of clay high in iridium found around the world, which is called the K-Pg boundry. This extinction allowed mammels to become the dominant form of life. During the Cretaceous period emerged marine reptiles, many mammels and birds, and flowering plants.
