Ornithopod
| Ornithopoda Fossil range: Lower Jurassic – Upper Cretaceous |
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| Ornithopod dinosaurs. Far left: Camptosaurus left: Iguanodon, centre: Shantungosaurus centre foreground: Dryosaurus, right: Corythosaurus, far right: Tenontosaurus. |
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Ornithopods are the infraorder of bird-hipped dinosaurs. They started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world.
Their major evolutionary advantage was the progressive development of a chewing apparatus that became the most sophisticated ever developed by a reptile. They had multiple teeth rows, cheek pouches and true chewing.[1] Efficient chewing means faster digestion, as the material is broken into smaller pieces.
They reached their apex in the duck-bills, before they were wiped out by the Cretaceous–Tertiary extinction event with all other non-avian dinosaurs. Members are known from all seven continents, although the Antarctic remains are unnamed, and they are generally rare in the Southern Hemisphere.
They are the sister group to the horned dinosaurs (Ceratopsia) and the hard-headed dinosaurs (Pachycephalosauria).
The duck-bills started out as small, bipedal running browsers, and grew in size and numbers. They became one of the most successful groups of herbivores in the Cretaceous world, and dominated the landscape. Their success is a perhaps surprising, as they have little obvious defence against theropod carnivores. They could run, and had the usual defences of a herd animal.[1] They had horny beaks and some cartilage rib plates. Iguanadons, however, could protect themselves. They were very robust (heavy and strong), and armed with a dagger-like thumb.
[change] Classification
Infraorder Ornithopoda
- Family Camptosauridae
- Family Dryosauridae
- Family Hypsilophodontidae
- Family Iguanodontidae
- Family Rhabdodontidae
- Family Hadrosauridae
