Silurian

The Silurians (known amongst themselves as Earth Reptiles) were Earth's first known sentient species. They were also referred to as Psionosauropodomorpha. Technologically advanced, they lived during prehistoric times.

Physical Appearance
Silurians were tall, some reaching up to 7 feet in height. They had long fingers and three webbed toes on each foot. Their mouths were small and somewhat sucker-like. The most noticeable feature of the Silurians were their three eyes. Their main eyes were bright yellow with cat-like pupils. The third eye was red and on the forehead, surrounded by a fluting bone structure. They also had external ears, capable of hearing all around themselves. (NA: Blood Heat)

The Silurians had a wide variation in appearance beyond these basics. The Silurians seen at Wenley Moor had green, lumpy skin, a large mouth, rectangular ears and an inset third eye. As well as having a more powerful third eye, they were active creatures who spoke quickly in a deep voice. (DW: Doctor Who and the Silurians) The Silurians seen on Sea Base 4, on the other hand, had a stockier build, brown skin, suckers on the tips of their fingers, a smaller mouth and the third eye on top. They also had ornate, curving spikes on their head and wore thick armour. They were also slower and spoke in a higher pitched voice. (DW: Warriors of the Deep)

Anatomy
Silurians were cold blooded and were only capable of surviving in warmer temperatures. They would become sluggish and slow when too cold. Silurians had a hunter's anatomy, with powerful muscles and hollow bones. Though they were taller than Humans, they were also lighter and faster. Silurians were incapable of crying. (NA: Blood Heat) The typical lifespan of a Silurian was 200 to 250 years. (MA: The Scales of Injustice)

The Sea Devils, though related to Silurians, were genetically divergent enough to create problems for the offspring of such matings. (MA: The Scales of Injustice)

Third Eye
The Silurians possessed a third eye on their forehead which allowed them to use a variety of telepathic powers.

The Silurians used their third eyes to communicate with other Silurians in a process known as "linking". The third eye would glow along with their emotions, becoming brighter when angered. They could also sense the presence of Silurians, even from great distances. Silurians were capable of controlling the minds of other creatures. (NA: Blood Heat) They were known to hypnotise and coerce Humans through a link to a primal part of their subject's mind, though stronger wills were capable of resisting this control. (BFA: Bloodtide)

The third eye was able of either simply harming organic beings, kill them or leave them unconscious. Alternatively, they were able to revive a Human that they had made unconscious through this third eye. Energies emanating from it allowed them to burn through walls and create tunnels. (DW: Doctor Who and the Silurians, NA: Blood Heat)

The Silurians also employed their third eye in more mundane tasks, such as activating their technology, opening passageways or creating forcefields to trap prisoners. (DW: Doctor Who and the Silurians)

Culture
The Silurians were described as generally a peaceful race with their highest laws preventing outright warfare except in the case of defensive engagements. (DW: Warriors of the Deep)

Silurians communicated by telepathically linking with the use of their third eye, as well as by body language. Though they could communicate with words, they generally only used it for effect, when talking to children or to species without telepathic linking abilities. Silurians had little in the way of literature, since their mind linking abilities were a more effective method of transferring ideas. (NA: Blood Heat)

Silurians of advanced age would festoon their third eye with pearls as a form of decoration. (NA: Blood Heat)

Some Silurians kept early homonids as pets. (Doctor Who and the Cave-Monsters)

Technology
The Silurians had many advancements unknown to the Humans. They had simple cryogenic technology, though it had a faulty timer and relied on nearby energy sources. They had some holographic technology as well. The Silurians processed their own food and didn't rely on harvesting animals or plants, (MA: The Scales of Injustice) except for times of food deprivation. (NA: Blood Heat) They also used mechanical airships, which Bernice used and found to be of high quality. (NA: St Anthony's Fire)

The Silurians had advanced genetic capabilities. They were capable of bringing species back from extinction, such as many species of dinosaurs. (DW: Doctor Who and the Silurians, NA: Blood Heat) They could also modify species, like they did with the Myrka. (DW: Warriors of the Deep) Furthermore, they demonstrated their ability in creating a genetically engineered plague, which they once used against early Humans who invaded their crop settlements. The disease was highly virulent to Humans and was used as a form of 'pest control'. (DW: Doctor Who and the Silurians) Despite this, they were still having problems with Silurian/Sea Devil hybrids' deficiencies. (MA: The Scales of Injustice)

Other noted technological abilities of the Silurians included the ability to disperse the Van Allen belt, which would have left Earth defenceless against cosmic radiation. (DW: Doctor Who and the Silurians) They could also modify the atmosphere, increasing the temperature in certain areas. (NA: Blood Heat)

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, though they used a Battlecruiser for transportation and offensive purposes. (DW: Warriors of the Deep) They could amplify the powers of their third eyes, allowing them to cause even more damage.

Original Rule
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. (DW: Doctor Who and the Silurians) In this time, they had built cities of metal millions of years ago which was the height of their civilization. However, some of their scientists such as Doctor Wolik believed that a large space moving object was destined to crash to their world. Despite their findings, some of the Silurians were cynical of this coming disaster with a few believing it to be a simple scare story. In time, they panicked at the coming event and decided to seal themselves into hibernation. During this time, primitive ape-like Man began to hunt in packs and began attacking the Silurians. (DWM: Twilight of the Silurians)

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. (DW: Doctor Who and the Silurians)


 * The time of this rule has never been consistently dated.

Re-awakenings
After millions of years, some of the Silurian Hibernation units had been awoken.

Charles Darwin and the HMS Beagle expedition, along with the Doctor and Evelyn Smythe encountered a rogue Silurian group in the Galápagos Islands. It was revealed that the leader of this group had been responsible for creating humanity's prehistoric ancestors via a forbidden breeding program. (BFA: Bloodtide)

At some point, H. P. Lovecraft discovered a reawakened settlement of Silurians who were freed from their hibernation by the machinations of The Master. However, they refused to follow him and decided to sacrifice both him as well as Lovecraft to their idol. During the event, Lovecraft stole a gemstone that was the key to the reactivation of the hibernation chambers and escaped with the Master to his TARDIS which was actually disguised as the sacrificial idol. Without the gemstone, the Silurians were forced to return to their sleep. (DW: Perfect Timing)


 * This may have inspired Lovecraft's writings and had him turn the Silurians into the Deep Ones from his stories.

Jules Verne and the Doctor once encountered Silurians and a giant squid. This adventure would be reworked into 20,000 Leagues Under the Sea, though the Doctor had some difficulties convincing Jules to remove the parts with the Silurians. (NSA: Peacemaker)

In the late 20th century a group of Silurians were awakened from hibernation by the energy from the nearby nuclear power research centre at Wenley Moor. After disagreement between Okdel and Morka over this course of action, Morka won out and the Silurians 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 afterward, a second base was awoken in Oregon, and was likewise dealt with by UNIT. (PDA: The Devil Goblins from Neptune)



Shortly afterwards, a different base of Silurians was found. They too wanted to take back Earth, and there was also a schism of power leading to the eventual second invasion. (MA: The Scales of Injustice)

In 1983, Sarah Jane Smith and K-9, while visiting Warren Martyn's archaeological expedition in Egypt, discovered an underground city of Silurians and Sea Devils. Sarah Jane opened diplomatic relations with them, and on her return to England, contacted the Brigadier, who was willing to make amends for his earlier mistakes. (DWM: City of Devils)

By 2003 there were Silurians serving as part of UNIT, in particular Imorkal, who was working with Liz Shaw at Tranquillity Moonbase on Earth's Moon. (NA: Eternity Weeps)

A number of decades later, General Sir Lethbridge-Stewart, helped the Silurians attempt to finally make peace with the humans, though the general public believed it to be a stunt involving men in rubber suits. (BFA: The Coup) Later, the Silurians aided UNIT in finding a cure for a new deadly plague. (BFA: The Wasting)


 * How this peace eventually breaks down into the open hostility some eighty years later at Sea Base 4 is not known.

Circa 2084, a group of Silurians allied themselves with the Sea Devils to invade Sea Base 4. They attempted to launch the Proton missiles to provoke a war between the two major power blocs. They were killed when the based was flooded with Hexachromite gas. (DW: Warriors of the Deep)

By the 26th century they had been accepted into Terran society, when the term "Earth Reptile" was apparently popularized among the Humans. (NA: Love and War)

Alternative histories

 * In one alternative version of the 1990s, the Doctor having died during the Wenley Moor incident, the Silurians ruled Earth unchecked, introducing dinosaurs into Earth's ecosystem. (NA: Blood Heat)
 * In another alternative 1990s, the Doctor died during the same incident. Silurians, Sea Devils and Humans live, however in peace, under the URIC or United Races Intelligence Command, formerly known as UNIT. (DWM: Final Genesis)
 * In a timeline diverging from the 1970s, the Silurians (refered to as "lizards") unleashed an army of dinosaurs on London. UNIT used time-travel technology to wipe out the Silurians with nuclear weaponry before they could wake up in the 1970s. (DWU: Sympathy for the Devil)

Other information

 * 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. The PDA The Quantum Archangel suggests that the Moon was orbiting the Earth before 150 million BCE, which means the Silurians ruled before then.
 * One account shows portrays Cybermen on Mondas discovering Silurians and Sea Devils during an unspecified time in the past. Whether these Earth Reptiles evolved on Mondas or were transported there is not clear. The strip also portrays Golgoth, a primordial god-figure, who resembles a Sea Devil and may have some link to the Silurians. (DWM: The Cybermen: The Dead Heart)
 * One account has the Silurians referred to by the Latin name Psionosauropodamorphae, which literally translates as psychic lizard-foot shaped. This may be intended to suggest a connection between the Silurians and the sauropod family of dinosaurs, though this seems unlikely given the near-total lack of physical resemblance and the comparatively small cerebral capacity of most sauropod dinosaurs. (NA: Blood Heat)

Background

 * A alien resembling a Silurian minus the obvious third eye will appear in series five, and though it is not yet clear whether this is a Silurian redesign it has been stated by some set reporters that it is.