CRETACEOUS PERIOD: 110 - 65 million years ago
Hadrosaurs were the most common, varied, and well-adapted ornithopod (bird-hipped) dinosaurs. The group probably evolved in central Asia and by the Late Cretaceous Period, had spread all over the lands of the northern hemisphere, migrating across a land bridge that existed at that time connecting Asia to North America. From there, the group moved eastward again to Europe. Remains of a certain type have even been found in southern Argentina, believed to be from a migration from North America across a volcanic island chain that once existed. Hadrosaurs were the first dinosaur family to be described in North America.
The outward appearance of hadrosaurs varied widely amongst the different species but structurally, they were all the same. The most obvious common feature was the elongated face ending in a broad, flattened snout. The toothless beak of the hadrosaur looked quite similar to the bill of a duck, hence the common nickname of these dinosaurs, "duck-billed dinosaur". Hadrosaurs were herbivores (plant-eaters) and only had teeth in the cheek area, not the front of the mouth. The many rows of teeth were perfect for effectively grinding up rough vegetation for easy digestion.
This unique group of dinosaurs grew in sizes over 40 feet and probably weighed over 5 tons! In-depth studies of a variety of duckbill remains indicate that these were strictly land-based dinosaurs that walked predominantly on all fours but had the ability to stand on their hind legs. In 1999, a remarkable discovery was made from the Hell Creek Formation where a mummified hadrosaur was discovered with skin, ligaments, tendons and what appear to be some internal organs. CT scanning of the specimen and further research will help scientists to further understand this and even other, dinosaurs.
Hadrosaur fossils have been found in China, North America, South America (Argentina) and Europe.
- image by Mineo Shiraishi