page_title: Hadrosaur diet
section_title: Early history of research
hierarchical_section_title: Hadrosaur diet / Early history of research
caption_attribution_description: Historical life restoration of “Hadrosaurus mirabilis” (i.e. Edmontosaurus annectens aka Anatoasaurus copei) by a lake.
context_page_description: Hadrosaurids, also commonly referred to as duck-billed dinosaurs or hadrosaurs, were large terrestrial herbivores. The diet of hadrosaurid dinosaurs remains a subject of debate among paleontologists, especially regarding whether hadrosaurids were grazers who fed on vegetation close to the ground, or browsers who ate higher-growing leaves and twigs. Preserved stomach content findings have indicated they may have been browsers, whereas other studies into jaw movements indicate they may have been grazers.
  The mouth of a hadrosaur had hundreds of tiny teeth packed into dental batteries. These teeth were continually replaced with new teeth.
  Hadrosaur beaks were used to cut food, either by stripping off leaves or by cropping. It is believed hadrosaurs had cheeks in order to keep food in the mouth.
  Researchers have long believed their unusual mouth mechanics may have played a role in their evolutionary success. However, because they lack the complex flexible lower jaw joint of today's mammals, it has been difficult for scientists to determine exactly how the hadrosaurs broke down their food and ate.
context_section_description: The first hadrosaur finds did not include much skull material. Hadrosaur teeth have been known since the 1850s (Joseph Leidy's Trachodon), and a few fragments of teeth and jaws were among the bones named Hadrosaurus by Leidy in 1858. (The skeletal mount made for Hadrosaurus by Benjamin Waterhouse Hawkins included a speculative iguana-like skull) Leidy had enough skeletal material to make other inferences about the paleobiology of hadrosaurs, though.  Of particular importance was the unequal lengths of the forelimbs and hindlimbs. He interpreted his new animal as a kangaroo-like animal that browsed along rivers, using its forelimbs to manipulate branches. His vague inference of amphibious habits would later be expanded upon by Edward Drinker Cope, who contributed the mistaken conclusion that hadrosaur teeth and jaws were weak and suitable only for eating soft water plants. 
  Cope described the next piece of the puzzle in 1874: a more complete jaw fragment in 1874 he named Cionodon arctatus, which revealed for the first time the complex hadrosaur tooth battery. However, the first essentially complete hadrosaur skull was not described until 1883. It was part of a skeleton (the first essentially complete hadrosaur skeleton as well) collected in 1882 by Dr. J. L. Wortman and R. S. Hill for Cope.  Described as a specimen of Diclonius mirabilis, it is now known as the type specimen of Anatotitan. Cope immediately drew attention to the anterior part of the skull, which was drawn out, long, and wide.  He compared it to that of a goose in side view, and to a short-billed spoonbill in top view.  Additionally, he noted the presence of what he interpreted as the remnants of a dermal structure surrounding the beak. Significantly, Cope regarded his Diclonius as an amphibious animal consuming soft water vegetation. His reasoning was that the teeth of the lower jaw were weakly connected to the bone and liable to break off if used to consume terrestrial food, and he described the beak as weak as well.  Unfortunately for Cope, aside from misidentifying several of the bones of the skull, by chance the lower jaws he was studying were missing the walls supporting the teeth from the inside; the teeth were actually well-supported. While Cope anticipated publishing a full report with illustrations, he never did so, and instead the first accurate illustrated description of a hadrosaur skull and skeleton would be produced by his great rival, Othniel Charles Marsh. While Marsh corrected several anatomical errors, he retained Cope's postulated diet of soft plants.  The description of hadrosaurs as amphibious eaters of aquatic plants became so ingrained that when the first possible case of hadrosaur gut contents was described in 1922 and found to be made up of terrestrial plants, the author made a point of noting that the specimen only established that hadrosaurs could eat land plants as well as water plants.
caption: Early restoration by Charles R. Knight of hadrosaurs as semi-aquatic animals that could only chew soft water plants, a popular idea at the time which is now outdated
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