Mammoth

Mammoths were a species native to Earth in prehistory.

Prehistory
In the pre-universe before the Time Lords created history, there existed cities carved into gigantic ivory tusks where scholars and philosophers rode on the backs of steam-powered mammoth skeletons. (PROSE: Christmas on a Rational Planet) The mammoths ruled these cities and were in turn ruled by Cernunnos. The mammoths created stone men and then used breeding-engines to create humanity.

After the creation of the Spiral Politic, Cernunnos ordered the humans to hunt mammoths to extinction. A trace of loyalty to mammoths remained in humanity's collective memory for billions of years. The ruins of one of the mammoths' ivory cities stayed hidden in an alter-time realm. (PROSE: Cobweb and Ivory)

Around 100,000 BC, Martha Jones watched herds of mammoths while the Tenth Doctor went to retrieve the bodies of Modrikanians who had died in a crash on Earth. (PROSE: Snowglobe 7)

Nimrod's Neanderthal tribe herded mammoths "sunward to find new grazing." (TV: Ghost Light) According to the Fourth Doctor, the Neanderthals could knock up a good Mammoth casserole. (PROSE: The Romance of Crime)

While being pursued by the Trods through time, the Second Doctor visited prehistoric Earth, where he used his recorder to befriend a herd of mammoths and get them to destroy the Trods' power supply. (COMIC: Pursued by the Trods)

The Ninth Doctor and Rose Tyler on a visit to prehistoric Earth encountered a mammoth killed by a Hy-Bractor. (PROSE: Only Human)

After being flung back in time by a Time Cube, the Fourth Doctor, Sarah Jane Smith and Dr. Bhoul encountered a caveman and a raging mammoth. (PROSE: The Time Snatch)

Circa 35,000 years ago, the Eleventh Doctor and Rory Williams visited the future site of Los Angeles, California, where the TARDIS became stuck in a tar pit. A mammoth was also stuck in the tar pit with them. (COMIC: The Doctor and the Nurse)

There was a picture of a mammoth in Malohkeh's database. (TV: Cold Blood)

Modern times
In 1774, King George III of the United Kingdom received a weakened Cerunnos as a gift from Catherine II of Russia. (PROSE: The Adventuress of Henrietta Street, Cobweb and Ivory, Grass, COMIC: Political Animals) As late as 1804, Thomas Jefferson believed that woolly mammoths still roamed the North American midwest and even sent an expedition to find one. (PROSE: Grass, The Adventuress of Henrietta Street)

In 1894, a spaceship containing temporal radiation exploded near the London Zoo, devolving one of its elephants to a mammoth. (PROSE: The Evolution Episode)

When Professor Grisenko discovered Skaldak encased in ice in 1983, he thought that he was a mammoth. (TV: Cold War)

In 2010, woolly mammoths were some of the prehistoric creatures brought into Sydney by chronal waves caused by the SKARDIS. (COMIC: The Age of Ice) In the same year, the Eleventh Doctor and Amy Pond encountered an alien spaceship disguised as a mammoth in New York City. (PROSE: The Forgotten Army)

In the posthuman era, Cernunnos was resurrected at Terra Primagenia. Returning to the remains of the pre-universe mammoth empire with the unwitting help of Avus, Cernunnos began planning to undo the anchoring of the thread in a War against the Great Houses. (PROSE: Cobweb and Ivory)

Alternate timelines
In an alternate timeline, the Silurians brought back the mammoths, raising them for food and allowing them to roam the mountains of Earth. (PROSE: Blood Heat)

In another alternate timeline, an American news anchor told her audience that the Holy Roman Emperor Winston Churchill had a "personal mammoth", and that he returned to the Buckingham Senate atop it. (TV: The Wedding of River Song)

Other planets
A zoo on an Earth-like planet exhibited a mammoth or a mammoth-like creature. (COMIC: The Didus Expedition)

The Junlangis of Dellah were white, mammoth-like creatures. (PROSE: Twilight of the Gods) Yahoomer's species resembled orange mammoths with four trunks. (PROSE: The Monsters Inside)

K9 once encountered some mammoths on an unnamed planet in another dimension, partially inhabited by ex-Tellac miners. They lived alongside other Earth animals from widely varying periods of evolutionary history. On this planet, he observed a mammoth fighting a sabre-toothed tiger. (PROSE: K9 and the Missing Planet)

Due to a fracture in time caused by the Last Great Time War, mammoths on Traxis coexisted with dinosaurs, neanderthals, and robots. (COMIC: Weapons of Past Destruction)