The earliest carnivorous dinosaurs, or meat-eaters, came in many different shapes and sizes. It is thought that the 20-foot-(6-meter-) long, Early Jurassic Dilophosaurus was a typical carnivore: This dinosaur had strong hind legs, but short, weak forelimbs. It also had thin parallel ridges on its forehead, which could have acted as radiators to control temperature, or as decoration, possibly for territorial or mating displays. The earliest herbivorous dinosaurs, or plant-eaters, also came in many different shapes and sizes. One typical herbivore was the Early Jurassic Heterodontosaurus, a small, turkey-sized dinosaur that had sharp incisors, canine-like tusks, and grinding teeth for chewing plants.