Thomas-saurus Rex is a book.
Thomas hears Gordon and James talking about Stepney and his "old load". The big engines think they are too important to pull it. Later, Percy asks Thomas if he knows what Stepney is bringing. Thomas tries lower his voice so that Gordon and James won't laugh at them. Thomas likes Stepney, and he likes the story of when Sir Topham Hatt and Grandfather Hatt got dirty when they rode in Stepney's truck full of coal, because the carriage's axle broke. Stepney asks Thomas what he thinks of his load. Thomas does not want to hurt Stepney's feelings, so he says it looks old. Gordon, James, and Sir Topham Hatt then arrive. Sir Topham Hatt asks if anyone will volunteer to help Stepney up the hill, so he can deliver the load to Tidmouth. Gordon and James do not want to help, so Thomas volunteers, and as they leave Sir Topham Hatt gives Gordon a stern look. When they arrive the children are amazed at what Thomas and Stepney have brought - a dinosaur skeleton.
- Sir Topham Hatt
- Grandfather Hatt (does not speak)
- Henry (only on the cover)
- Dowager Hatt (mentioned; not named)
- The book suggests that Sir Topham Hatt use to be called "Little Topham Hatt" in his youth.
- The cover shows Henry, but in the story, Gordon is in his place.
- The treasure chest is not on the cover.
- In the first illustration, a building was replaced by two rails and a water tower.
- Sir Topham Hatt was not dirty in the final illustration.
- Wooden Railway (Stepney with Museum Cars and Thomas-Saurus Set; discontinued)