Below is a list of all the removed animals and dinosaurs in the series:
Plateosaurus was going to be in the first episode but the Triassic was scrapped
and became the Cretacieous.Sellosaurus was also going to be in episode 1. It was replaced by Onchopristis.
Unicerosaurus was a fish that was going to be in a now scrapped episode, Dinos and Fish
Velociraptor was origially going to be in Planet Dinosaur (excluding the database). it was replaced by Saurornithoides.
Sinosauropteryx originally had a role as a creature. It was then scrapped and put in a database.
Aetosaurus was planned but its role was taken by Sarcosuchus.