Our Pteranodon family is on the beach watching small eggs hatch and baby Archelon turtles emerge, and start to swim away. Our family and Mr. Conductor get into the Dinosaur Train Submarine and follow the baby Archelons who discover their own facts of nature - that their mother doesn't stay with them after they're born, and that they will grow up to be giant-sized sea turtles. Tiny and Buddy find out that a newer train will be riding the same tracks as the Dinosaur Train. The new train is called the Rocket Train, and its conductor is named Thurston Troodon, who was a former classmate and rival of Mr. Conductor. Thurston is very confident and boasts that the Rocket Train is newer, better, and faster than the "old Dinosaur Train." Mrs. Troodon, Thurston, and Mr. Conductor's old teacher, suggests a friendly train race. With Tiny and Buddy on board, the "old" Dinosaur Train ends up helping out Thurston and the new Rocket Train after it breaks down.