A plesiosaurus is a marine dinosaur whose compact body is driven by powerful flippers. Predatory and aggressive, it attacks any creature it encounters. Its flexible neck accounts for a third of its total length, letting it twist in any direction to deliver a powerful bite.

Dinosaurs

Dinosaurs, or behemoths, are among the oldest reptiles in the world. Predatory dinosaurs are savage, territorial hunters. Herbivorous dinosaurs are less aggressive, but they might attack to defend their young, or if startled or harassed.

Dinosaurs come in many sizes and shapes. Larger varieties often have drab coloration, while smaller dinosaurs have colorful markings akin to birds. Dinosaurs roam rugged and isolated areas that humanoids seldom visit, including remote mountain valleys, inaccessible plateaus, tropical islands, and deep fens.

A prehistoric aquatic reptile with a flat body, short tail, and long neck

Elasmosaurus is a member of the plesiosaur family of prehistoric aquatic reptiles; they are not properly dinosaurs, but are included here as they were contemporaries. Plesiosaurs have flat bodies, short tails, and long necks; where a quadrupedal animal would have legs, they have flippers. As they are reptiles, they cannot breathe underwater, though they can hold their breath for an extended period. They are aggressive carnivores, subsisting on fish and small non-aquatic animals, which will be pulled below the surface and drowned. On any successful hit, an elasmosaur has established a hold on the victim, who will then be pulled into and under the water unless they can make a successful save vs. Death Ray to break free. An elasmosaur is not strong enough to thus move any creature weighing more than 300 pounds.

Cretaceous carnivore

None of these creatures are technically dinosaurs, though all are found in "Lost World" areas. Elasmosaurus can also swallow whole, needing only 18-20 on its "to hit" roll to do so but otherwise as dunkleosteus. Cretaceous carnivore.