The Last Dodo — Jacqueline Rayner

After a trip to the zoo, the Doctor and Martha go in search of a real live dodo, and are transported by the TARDIS to the mysterious Museum of the Last Ones. There, in the Earth section, they discover every extinct creature up to the present day - billions of them, from the tiniest insect to the biggest dinosaur, all still alive and in suspended animation.

Preservation is the Museum's only job - collecting the last of every endangered species from all over the universe. And for millennia the Museum has been trying to trace one elusive specimen: the last of the Time Lords...