A deinonychus was a type of dinosaur. The Fifth Doctor recognised a plaster footprint found in Eternity, California as belonging to a deinonychus. (PROSE: A Town Called Eternity)
On an alternate earth where the Silurians took over, Deinonychus were one of the many specimens bought back from extinction. They were known to gather in huge numbers and attack the surviving human settlements. (PROSE: Blood Heat)