Colorful World: Prehistoric

In each of the Colorful World board books, on each of their pages, there is a collection of things, and a different puzzle to solve (and something to learn about nature at the same time).
 
Look carefully! Something’s not the same in the Prehistoric ... Find what’s different!
 
Which triceratops is missing something? Find the one that is not an ankylosaurus. Which spinosaurus is wrong? Who is swimming the other way?