The cryptoclidus are grey or yellow fish-eating plesiosaurs who inhabit the planet Cryptos and have a sizeable fishing colony on the planet Aqua Minor. They can swim well, using four paddle-like flippers to travel through the water with ease. Cryptoclidus can also travel on land, although they are more awkward there. The colony's leader is the well-meaning but hasty Cripes. The cryptoclidus are not herbivores, eating fish as well as ammonites and belemnites, but most are friendly to the DSS. However, two cryptoclidus were leading members of a group of criminal sea reptiles called the Doom-Flipper Gang. The inventor Zindi Bent is also a cryptoclidus.