A Cryptoclidus is an aquatic Dinosaur with flippers that he is From The Land Before Time 4: Journey Through the Mists.
Role's in the film
The Land Before Time 4: Journey Through the Mists
It is a type of Swimming Sharptooth, that appeared near the end of The Land Before Time IV: Journey Through the Mists. After Dil swatted Ichy away, with her tail, she swam off defiantly. However, then, she met the Cryptoclidus, which roared, and started to chase after her. She called for Ichy, to come and rescue her, but he didn't arrive (because he didn't or wouldn't hear Dil's cries for help). It is currently unknown, as to whether or not Dil (or Ichy, for that matter) survived, or if she got eaten, since her death was not shown, on-screen, and the villainous pair have not had any subsequent appearances, yet, so far.