Endangered animals：12 endangered animals

The second, or Devonian-Carboniferous, mass extinction came about 367 million years ago. It lasted for three million years, during which time 82% of existing species disappeared. The causes included a proliferation of algae from the emergence of land-based plants that, by turning the soil, released nutrients into the ocean. The algae, by taking oxygen from the water, caused the disappearance of much of marine animal life.

The third mass extinction event took place 251 million years ago. Also known as the Permian-Triassic extinction, the process lasted one million years and led to the disappearance of 96% of species. The reason? Volcanic activity—which, according to scientists, perhaps also contributed to the disappearance of 76% of species during the Triassic-Jurassic event, the fourth mass extinction. That event took place 210 million years ago and lasted a million years.

The fifth mass extinction came about 65 million years ago, and saw the end o...