The Polacanthus encountered by the Fourth Doctor. (PROSE: The Doctor Who Dinosaur Book)
Polacanthus was a Dinosaur species which lived in the part of the world that later became England and Northern Europe. It was a "slimmer relative" of the Ankylosaurus; instead of armour plating, its back was protected by rows of sharp "horns". The Fourth Doctor pointed one out to his companion during a trip back in time to the Age of the Dinosaurs. (PROSE: The Doctor Who Dinosaur Book)
