Ornithopods 1 were a group of ornithischian (“bird-hipped”) dinosaurs. These bipedal and quadrupedal herbivores had a horny beak, plant-cutting or grinding cheek teeth, and a pelvic and tail region stiffened by bony tendons. They evolved teeth and jaws adapted to pulping vegetation and flourished from the Middle Jurassic to the Late Cretaceous period (165–65 million years ago) in North America, Europe, Africa, China, Australia, and Antarctica. Some ornithopods were no larger than a dog, while others were immense creatures up to 49 ft (15 m) long. Iguanodonts, an ornithopod group, had a broad, toothless beak at the end of a long snout, large jaws with long rows of ridged,
closely packed teeth for grinding vegetation, a bulky body, and a heavy tail. Iguanodon and some other iguanodonts had large thumb-spikes that were strong enough to stab attackers. Another group, the hadrosaurs, such as Gryposaurus and Hadrosaurus, lived in Late Cretaceous times (97–65 million years ago) and with their broad beaks are sometimes known as “duckbills.” They were characterized by their deep skulls and closely packed rows of teeth, while some, such as Corythosaurus and
Lambeosaurus, had tall, hollow, bony head crests.
