Spiny anteater
From Tardis Wiki, the free Doctor Who reference
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. (NSA: The Last Dodo)