Characters (or more accurately, animals) that belong to the clade Dinosauria, which includes 2 Orders Saurischia and Ornithischia.

Note that not all reptiles from the Mesozoic era (such as pterosaurs, mosasaurs, plesiosaurs, etc) or any prehistoric reptilian-looking animals (e.g Dimetrodon) are dinosaurs as commonly mistaken, so do not add this category to any prehistoric animal that is not a dinosaur.

Also, animals within the Dinosaurs category should not be in the Dragons category simultaneously, unless it is a verse's specific mechanics (e.g. Tyrantrum is in both categories, due to being both based on the dinosaur Tyrannosaurus rex and classified as a Dragon type).

This category also includes creatures that are based on dinosaurs, such as several Pokémon and Digimon, kaijuu that evolved from dinosaurs (e.g. Gorosaurus and Anguirus), or the Dinobots.

Birds do have their own category.