Permian

Permians (named by the Fifth Doctor after their native time period) were predatory creatures native to Earth around 260 million BC.

Biology
Permians appeared to be animated skeletons of theropod dinosaurs, their bodies composed of bone and cartilage and held together by a bioelectric field generated by the brain. They also used this field to hunt their prey, first by inducing a state of fear in their minds, then by consuming them, stripping the flesh from bone more efficiently than chewing could manage. Permians could assume the genetic characteristics of their prey; when one consumed a human, it became larger and more intelligent.

Permians could harness the natural forces of the world, except for fire, which was too volatile for them to handle. They were vulnerable to synthetic materials.

History
The Permians were such efficient predators that they hunted 96% of life on the planet to extinction, and with their food supply gone, they went dormant.

In 1964, an archaeological dig in Alaska led by Tulung's father and Shaun Brett's father unearthed a Permian fossil, which revived and attacked them. While Brett abandoned the site and fled in the plane, Tulung's father used dynamite to destroy the creature.

In 1994, Shaun Brett, who was building a monument to his deceased father, unknowingly used Permian fossils as part of its construction. The close proximity of the two creatures' bioelectric fields caused them to revive. The process was initially unfocused, inadvertently creating monstrous hybrids. They eventually freed themselves from the rock and began hunting again, starting with Gaborik. The Doctor, having discovered them by tracking their energy readings and knowing the threat they posed to the world, killed them by burning down Brett's monument with them inside. (BFA: The Land of the Dead)