|Average height||40 meters|
|Average length||100 meters|
|Average weight||3,000 tons|
|Place of origin||Earth|
|Behind the Scenes|
|Universe||Godzilla: The Series|
|Performed by||Whale sounds|
Cryptocleidus is a plesiosaur kaiju that first appeared in the 1998 Godzilla: The Series episode "Leviathan".
Cryptocleidus were aquatic long-necked reptiles, or plesiosaurs, that went extinct at the end of the Cretaceous period, in 65,000,000 B.C. However, it seems a number of the Cryptocleidus somehow survived extinction.
A Cryptocleidus appeared and attacked H.E.A.T.'s submarine until Zilla Junior appeared and started to fight it, just as H.E.A.T. discovers a Tachyon ship in the bottom of the ocean. When H.E.A.T. get out of the Tachyon ship, another Cryptocleidus appears. Zilla Junior tries to evade them and eventually hits a rock formation, causing the two Cryptocleidus to be crushed by the rock slide. During the event of Monster Wars, one of the Cryptocleidus survived and was spotted swimming towards Site Omega. It attacked H.E.A.T.'s boat and was tricked into fighting the Giant Bat. After the fight was broken up, both mutations traveled to Site Omega. Once the aliens began their assault, Cryptocleidus attacked Hong Kong. When the alien control was severed, Cryptocleidus was killed by the Tachyon ship's beams.
- Needless to say, the real life Cryptoclidus didn't even come close to the size depicted here. It also lived in the mid-Jurassic period, rather than the late Cretaceous.