Tricey was the name given by the Eleventh Doctor to a Triceratops he encountered on the Silurian Ark.
Biography
More information from Dinosaurs on a Spaceship and information from Legacy needs to be added.
Tricey behaved somewhat like a dog, fetching Brian Williams's golf ball and enjoyed being patted by the Doctor. Tricey was used by the Doctor and his friends as a mount to escape Solomon's robots on one occasion. However, soon afterwards, Tricey was shot and killed under Solomon's orders to demonstrate his seriousness. The Doctor comforted Tricey as it died. (TV: Dinosaurs on a Spaceship)
Legacy
When the Doctor wrote about the Silurian Ark in his diary, he included a photograph of Tricey. (PROSE: The Doctor's Diary [+]Moray Laing, The Official 50th Anniversary Annual (Penguin Group, 2013). Page 8.)