- You may be looking for the species named after the period.
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)