In their own way, ornithopods--the small, mostly two-legged herbivorous dinosaurs of the Mesozoic Era--have had a disproportionate impact on the history of paleontology. By a geographical fluke, many of the dinosaurs dug up in Europe in the early 19th century happened to be ornithopods (the most noteworthy being Iguanodon), and today more ornithopods are named after famous paleontologists than any other kinds of dinosaur. (See a gallery of ornithopod piotures.)
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Ornithopods (the name is Greek for "bird-footed") are one of the classes of ornithischian ("bird-hipped") dinosaurs, the others being pachycephalosaurs, stegosaurs, ankylosaurs and ceratopsians. The most well-known subgroup of ornithopods are the hadrosaurs, or duck-billed dinosaurs, which are discussed in a separate article; this piece focuses on the smaller, non-hadrosaur ornithopods.
Technically speaking, ornithopods (including hadrosaurs) were plant-eating dinosaurs with bird-shaped hips, three- or four-toed feet, powerful teeth and jaws, and a lack of the anatomical "extras" (armor plating, thickened skulls, clubbed tails, etc.) found on other ornithischian dinosaurs. The earliest ornithopods were exclusively bipedal, but the larger species of the Cretaceous period spent most of their time on all fours (though it's conjectured that they could run on two feet if they had to get away in a hurry).
Ornithopod Behavior & Habitats
Paleontologists often find it helpful to infer the behavior of long-extinct dinosaurs from the modern creatures they most resemble. In that respect, the modern analogs of ancient ornithopods seem to be herbivorous mammals like deer, bison, and wildebeests. Since they were relatively low on the food chain, it's believed that most genuses of ornithopod roamed the plains and woodlands in herds of hundreds or thousands, to better protect themselves from predators, and it's also likely that they took care of their hatchlings until they were able to fend for themselves.
Ornithopods were widespread geographically; fossils have been dug up on every continent except Antarctica. Paleontologists have noted some regional differences between genuses: for example, Leaellynasaura and Qantassaurus, which both lived in near-Antarctic Australia, had unusually large eyes, presumably to make the most of the limited sunlight, while the north African Ouranosaurus may have sported a camel-like hump to help it through the parched summer months.
As with many types of dinosaurs, our state of knowledge about ornithopods is constantly changing. For example, recent years have seen the discovery of two enormous genuses, Lanzhousaurus and Lurdusaurus, which lived in mid-Cretaceous Asia and Africa, respectively. These herbivores weighed about 5 or 6 tons, making them the heaviest ornithopods until the evolution of plus-sized hadrosaurs in the later Cretaceous--an unexpected development that has caused scientists to revise their views of ornithopod evolution.
Next Page: Ornithopod Controversies, and a List of Notable Genuses
