Creature type (Dungeons & Dragons) all animal type monsters are based on real world animals. Creature entries based on mythological, fictional, or nonexistent animals are usually classified as magical beasts (see below). Besides ordinary fish, birds, reptiles and mammals, the animal type is also applied to depictions of dinosaurs, prehistoric animals, and "dire" or specially modified, often larger and scarier, versions of real world animals. Some real world animals are not given the animal type in the game. Examples include arthropods (insects, spiders, etc.) and worms, which the game classifies as "vermin" (see below) and not animals. Mollusks, such as octopuses, are often classified as
Type system when called, at run-time. Duck typing differs from structural typing in that, if the "part" (of the whole module structure) needed for a given local computation is present "at runtime", the duck type system is satisfied in its type identity analysis. On the other hand, a structural type system would require the analysis of the whole module structure at compile time to determine type identity or type dependence. Duck typing differs from a nominative type system in a number of aspects. The most prominent ones are that for duck typing, type information is determined at runtime (as contrasted to compile