Silurian

The Silurians are a race of reptile humanoids native to Earth. The Silurians were Earth's first known sentient species, were scientifically advanced, and lived during prehistoric times.

Appearance
Silurians are a very diverse species, with at least two known types. In general, Silurians are roughly the size of humans, with a large head and green scaly skin. Their mouth is small and somewhat sucker-like. The noticeable features of the Silurians are their three eyes. Their main eyes are bright yellow with cat-like pupils. The third eye is red and is on their foreheads. They can use this third eyes for a variety of purposes. The Silurians from their first appearance used them for stunning or killing their opponents, signalling each other, or opening Silurian made doors. (DW:Doctor Who and the Silurians) The Silurians from 2084, on the other hand, had eyes that merely glowed whenever they spoke. (DW:Warriors of the Deep)

The Silurians seen in their first encounter had green, lumpy skin, a large mouth, rectangular ears and an inset third eye. (DW:Doctor Who and the Silurians) The Silurians seen in 2084 had a stockier build, brown skin, a smaller mouth and the third eye on top. (DW:Warriors of the Deep)

The Sea Devils are also closely related to Silurians, though far enough apart genetically to create problems for the offspring. (DW: The Scales of Injustice)

Technology
The Silurians aren’t much more advanced then the humans of the 1900s. They have simple cryogenic technology, though it had a faulty timer and relied on nearby energy sources. Though they could use their genetic technology to create such creatures as the Myrka, they were still having problems with Silurian/Sea Devil hybrids’ deficiencies. They had some holographic technology as well. The Silurians processed their own food and didn’t rely on harvesting animals or plants. (DW: The Scales of Injustice)

Though the Sea Devils used sonic weaponry, the Silurians relied on the Sea Devils and their third eye for defensive purposes. As such, the Silurians tended not to use weaponry.

History
At some point in Earth’s history, the Silurians were the rulers of the planet. They were led by the Triad and used the Sea Devils as soldiers. Eventually, they discovered a large planet coming dangerously close to Earth. This panicked the Silurians, who sent themselves into hibernation to protect their species. Though this planet was actually just the moon, the hibernation technology was faulty. After millions of years, some of the shelters have been awakened. (DW:Doctor Who and the Silurians)

Their first appearance took place in the 1980s. In it, a group of Silurians were awakened from hibernation by the energy from the nearby nuclear power research centre. The Silurians (after a schism of power) then attempted reclaim the planet from humanity by releasing a deadly virus. This plan was stopped by UNIT and the Doctor. Despite the Doctor's best efforts to broker a peaceful solution, the Silurian base was bombed by UNIT on Brigadier Lethbridge-Stewart's order. (DW:Doctor Who and the Silurians) Shortly afterwards, a different base of Silurians was found. This also introduced the Silurian/Sea Devil hybrids and had an reference to the Myrka. (DW: The Scales of Injustice)

Another group of Silurians allied themselves with the Sea Devils, in a second attempt to reclaim Earth from the humans. That attempt took place circa 2084. The Silurians also used a living weapon, the Myrka. (DW:Warriors of the Deep)

Silurians have also made many minor appearances, as they have been accepted into Terran society by Bernice Summerfield's time, when the term "Earth Reptile" was apparently popularised. (DW: New Adventures)

Trivia

 * The Silurians have never been accurately dated. As implied by their names, they were first said to be from the Silurian period (roughly 440 million to 415 million years ago), though this was before the first reptiles had evolved. The Third Doctor stated they were from the Eocene period (roughly 55 million to 35 million years ago), but this was after the extinction of the dinosaurs (which the Silurians were shown using). The Silurians were also seen using a map of Pangea from around 200 million years ago.

Television

 * Doctor Who and the Silurians
 * Warriors of the Deep

Spin-off novels

 * Blood Heat
 * The Scales of Injustice

Audio spin-offs

 * Bloodtide
 * UNIT: The Coup