Permian period

The Permian was a period of Earth history. It was part of the Palaeozoic Era. (PROSE: The Southwell Park Mermaid)

Permians, as named by the Fifth Doctor, were predatory creatures native to the Permian period around 260 million BC. They hunted 96% of life on Earth to extinction and went dormant. (AUDIO: The Land of the Dead)

According to the Seventh Doctor, a methane release at the end of the Permian killed nearly all life on Earth. Horseshoe crabs were one of the few organisms to survive. (PROSE: The Southwell Park Mermaid)