The Paleozoic Era, which marked the appearance of almost all animal phyla within a few million years, was ended by a mass extinction. The mass extinction was the virtual opposite of what started the era, with over 90 percent of the world's life being wiped out. Recovery from this mass extinction took almost 30 million years.
There are many subsections in the Paleozoic Era, breaking up the millions of years into smaller chunks. The end of the Paleozoic era is called the Permian era. This era saw numerous climate changes along with fluctuations in the carbon dioxide and oxygen levels. There are numerous hypotheses about what caused the extinction at the end of the Permian era, including the sea venting hydrogen sulfate, a huge meteor in Antarctica or even all of the possibilities combined into one.