Elephant

An elephant' was a type of animal that was found on the planet Earth.

Among the prizes that the Doctor obtained during a game of backgammon against Kublai Khan in the 13th century were 35 elephants with ceremonial bridles. (DW: Marco Polo)

The Levantines from Oroobia were similar to elephants and had rubbery ears and thick skin. (NSA: The Doctor Trap)

The size of the alien Wurm was comparable to the size of elephants. (NSA: The Art of Destruction)
 * No elephant has ever actually been seen in a televised episode of Doctor Who, and descriptions of them have been skimpy at best. Therefore, it's difficult to say with authority exactly what an elephant is in the Doctor Who'' universe.