|Name||Great A'Tuin to Discworld scholars (What It calls Itself is unknown)|
|Books||The Colour of Magic, The Light Fantastic|
|Cameos||always there, of course|
Great A'Tuin is a turtle. So what if it has four World Elephants and a disc-shaped world on top of it? It's still a turtle, of the species Chelys galactica. Nobody knows where it goes, or why, except probably Great A'Tuin itself. Its gender is unknown too, even though a space ship has been built to go and have a look. It has been known to alter its course to avoid meteorite hits, and even to snap at them with its beak or send them away with its flippers; whereas on less sensibly-designed worlds people have to rely on Bruce Willis.
The suspicion arises that if the Discworld was originally meant to have five world-supporting elephants and one of them got "lost", then this makes the Disc strange and unique even by the standards of those worlds travelling through space supported on the shoulders of world-bearing elephants who in turn stand on the back of a giant chelonian. Could this deficiency in the cosmic pachydermian stakes explain much that is odd about the Disc?
We can infer that this is not the only Discworld in the known universe: refer to the conclusion of The Light Fantastic, where eight eggs hatch into eight baby Discworlds, which are no doubt travelling through Space and spreading the astrochelonian model of world formation, much to the disbelief and consternation of any astronomers looking upwards through telescopes from less favoured worlds. (Note that the baby turtles each had four baby elephants on board.)
The Light Fantastic might also offer an inferred clue to the gender of Great A'Tuin - just as we speak of Mother Earth, is it possible that this is a nurturing Mother Turtle, who popped back to see if the eggs were all right? In which case, either parthenogenesis applies, or the mating of two star turtles occurred, very very carefully (much more so than Discworld philosophers fear - although this may have been the trigger event causing the Fifth Elephant to lose its footing and fall off the turtle?), a long time ago, before the evolution of sentient life, and it's taken this long for the eggs to incubate in the light of the red sun.
Alternately, Chelys galactica may mate belly-to-belly: a configuration that would drown at least one participant in a sea-dwelling turtles' tryst, but protect the passengers of both space-dwelling star turtles. In that case, even the Krullians wouldn't have had enough of a view to discern details, thus preserving the gender mystery.