Spiny anteater

The spiny anteater was one of the billions of entries in The I-Spyder Book of Earth Creatures. At some point, and for unknown reasons, it became extinct on Earth. In her quest to get a certificate from the Big Chief I-Spyder, Martha Jones never spotted one. Consequently, its I-Spyder point value was unknown. (PROSE: The Last Dodo)

Behind the scenes
In the Doctor Who universe, spiny anteaters are referred to only by that name, but in real life, the title can apply to both the long-beaked echidna and the short-beaked echidna. It is unknown which one The I-Spyder Book of Earth Creatures refers to.