Neutrals exist. They have no major issues with vivosaurs of other types, and are generally easy to care for. Getting the most out of them is where the challenge lies. Often times they have special skills and abilities that make them interesting and unique choices for battlers and friends. Treat 'em right, and they won't let you down.
Neutral vivosaurs can harness a form of pure energy related to the elemental square, but unaffected by any of its sides. Aside from that, they're the closest in biology to true dinosaurs (or other prehistoric animals. Looking at you, Titanis.)
Most neutral vivosaur personalities fall into one of two categories: quiet and calm or hyperactive. Many of the latter are lighthearted pranksters who spook their trainers or other small creatures (relatively speaking) for fun. No harm is usually intended, and in time they'll develop a better sense of comedic timing.