Devonian-Silurian Extinction Essay

1298 Words3 Pages

Riley 6
recognizable evidence for animals was discovered in Oman, this discovery revealed small sea sponges that were alive approximately 635 million years ago.” -Oldest fossil evidence for animals found. Nearing 443 million years ago occurred the third largest extinction in Earth’s history the Ordovician-Silurian extinction, during this extraordinary event almost 85% of all sea life had been wiped out. Preceding this event a giant formation of ice was collecting in the southern hemisphere. It was proposed that this sheet of ice had lowered sea levels and messed with ocean chemistry.
The Devonian Period was between 416 million and 358 million years ago. During this fundamental period sea life grew exponentially with the introduction of new organisms such as trilobites, and Placoderms (armored fishes). Towards the end of this period there was another mass extinction resulting in one third of all species on Earth becoming extinct this extinction is called the Late Devonian extinction. The best possible cause of this was an impact event caused by a huge meteor. With left the oceans in a state devoid of oxygen the only possible creature able to …show more content…

However, it would not be until the dinosaurs went extinct that the mammals would flourish. The evolution of the first mammals had occurred towards the end of the triassic period. Their ancestor who can link this evolution to is the therapsids. The first mammals were small, which was an advantage during the time of the dinosaurs. Since nearly all of the carnivorous dinosaurs were large, the smaller the mammal the more likely it will survive. The extinction of the dinosaurs was most likely caused by a huge meteor colliding with the Earth which is known as the Cretaceous-Tertiary extinction extinction. This

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