Great A'Tuin

Great A'Tuin is the giant star turtle who travels through space, carrying the four giant elephants (named Berilia, Tubul, Great T'Phon, and Jerakeen) who in turn carry the Discworld. A member of the species Chelys galactica, A'Tuin is the only turtle to ever feature on the Hertzsprung-Russell diagram. Its shell is frosted with frozen methane, pitted with meteor craters, and scoured with asteroidal dust.

Great A'Tuin's sex is unknown, but is the subject of much speculation by some of the Discworld's finest scientific minds - in an analogy to astrophysicists, specialists in this field are called astrochelonians.The sex of The World Turtle is pivotal in proving or disproving a number of conflicting theories about the destination of "Great A'Tuin's" journey through the cosmos. If (as one popular theory states) "Great A'Tuin" is moving to his (or her) mating grounds, then at the point of mating might the civilisations of the Discworld be crushed or simply slide off? Attempts by telepaths to learn more about Great A'Tuin's intents have not met with much success, mainly because they did not realise that its brain functions on such a slow timescale.

Following the events in The Light Fantastic, Great A'Tuin attended the hatching of eight baby turtles, each with four baby elephants and a tiny Discworld of their own. They have since gone off on their own journeys.The Great A'Tuin frequently rolls on its belly to avoid asteroid and comet collisions. This doesn't affect the Discworld's population, other than to induce severe seasickness on anyone who happens to be looking at the night sky at that time. A'Tuin has been known to do more complex rolls and corkscrews, but these are rarer.

A tiny sun and moon orbit the Great A'tuin, both about one mile in diameter when described at the start of the series, but the description of their diameter is increased to at least eighty miles later in the chronicles. The moon is slightly closer to the Discworld than the sun, and is covered, on one half, with silvery glowing plants, which feed the lunar dragons. The other half is burnt black by the sun. The moon rotates, and completes a full revolution in about a month; the full moon occurs when the luminescent side is completely visible from the Discworld, the new moon when the dark side is shown. Also, the sun's orbit is so complex that one of the elephants has to cock its leg to allow the sun to continue on its orbit.

A'Tuin is also orbited by a number of small "planets" made from the droppings of the elephants by giant dung beetles.