When the Pteranodon family spots Annie and her T. rex herd migrating to follow the food, the Pteranodon kids wonder if other creatures, even marine mammals, also migrate. The Conductor flies the Pteranodon family over the ocean in the Dinosaur Train Zeppelin to look for Polycotylus, a type of marine reptile that does migrate in the ocean. After spotting a pod of migrating Polycotylus from the sky, the Zeppelin lands in an atoll and our family meets Paulette and Polly Polycotylus, a mother and daughter (from what is modern-day Australia.) Our Pteranodon kids, and Mom, Dad and the Conductor learn all about Polycotylus migration and the reptile features. Then the whole group of new friends enjoys a fish-picnic on the reef of the atoll before the Pteranodon clan heads back home in the zeppelin.