The Gnathostomata, all fishes other than agnathans and the tetrapods, are marked by the possession of jaws, a feature that opened an enormous number of adaptive pathways that were closed to agnathans in terms of diets and food-handling techniques. Jaws allowed gnathostomata to adopt a truly predatory mode of life for the first time: only jaws can grip a prey item firmly, and allow it to be manipulated, cut cleanly, and ground up, How did jaws evolve.