It is a long, tall, orange reptile with red spots on its back and neck. It has short, smaller legs and red around its eyes.It also appears to have a very wrinkled mouth.
Role in episode
While Ginger and the other lost kids chase SpongeBob through the Lost and Found, they pass through the lost world. SpongeBob rides on a Tylosaurus, while Ginger and the other lost kids ride in a box on a Tanystropheus' back.
At the end of the episode, when Squidward is lost in the lost world, a Tanystropheus can be seen walking around.
Role in Lost Treasures
A Tanystropheus reappears as an obstacle in level 5. Like "Lost and Found," it carries the lost kids on its back.