Unknown (possibly a female)
Slate Gray (original)
Frank Welker (stock sound effects only)
A "Swimming Sharptooth" makes a small appearance in The Land Before Time IV: Journey through the Mists. It lives in the Mysterious Beyond, and possibly lives in a river area, as it appears there in the film. Though what specific genus of plesiosaur it is intended to represent is unknown, a number of fans believe that it is a Hydrotherosaurus or a Pleisiosaurus.
It appears near the end of the film, after Ichy and Dil part ways. After Dil swats away Ichy with her tail, she bumps into the plesiosaur, who subsequently chases the Deinosuchus away. It is unknown if Dil survived the encounter, or if she was ultimately eaten by the much larger plesiosaur. It is likely that she did not escape the much faster and keen sighted plesiosaur.
- The swimming sharptooth's color is brown instead of gray in the 2014 remastered DVD re-release of the film.
- The plesiosaur is the fourth Swimming Sharptooth to appear in The Land Before Time franchise.
- This plesiosaur is the first and so far only one of its species in the franchise.
- It is the first plesiosaur to appear in the franchise.
- It bears a slight resemblance to the famous Loch Ness Monster that is believed to live in Loch Ness, Scotland.
- The plesiosaur looks similar to a real Elasmosaurus, but Elsie, who is confirmed to be an Elasmosaurus from The Land Before Time V: The Mysterious Island, looks different, due to her having a crest on her head.