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The Ornithopoda are a group of medium to large plant-eating dinosaurs. They include the "hypsilophodontids" (not discussed here) and the Iguanodontia. The crested and "duck-billed" hadrosaurs are iguanodonts. Several of these are noted for the spacious and bizarrely shaped sinus regions in their skulls. All ornithopods were herbivores and mostly bipedal.
There are two subfamilies of hadrosaurs, the Lambeosaurinae, which have a crest on the skull (like the top skull at right), and the Hadrosaurinae, which lacked the crest (like the bottom skull at right). The crest on a lambeosaur's skull contains the nasal passages, which "looped" through the crest and often formed sizeable chambers before passing into the airway. Why the crest? A number of hypotheses have been seriously suggested:
The most accepted theory today of the function of the crest is that it served as a resonating chamber, allowing lambeosaurs to make deep, loud sounds. Perhaps these calls warned of predators, or kept a herd together, or attracted potential mates, or did all these things. The crest may have also functioned as a visual display device in addition: perhaps large and odd-shaped crests attracted mates.
Now let's meet some of the duckbilled dinosaurs. Both Maiasaura and Edmontosaurus are hadrosaurines; they lack the crests of the lambeosaurs.
See Parasaurolophus, a crested lambeosaur, as it was exhibited in UCMP's former home in Minor Hall.
A newly hatched hadrosaur was less than 14 inches long and weighed about 1.5 pounds. What did these baby dinosaurs eat? They ate fruits, leaves and other plant material that may have been brought to the nests by their parents. Since the parent duckbills were nearly 30 feet long and weighed about three tons, we assume that the dinosaurs were too large to incubate their eggs by sitting on the nest. Instead, warming for the eggs was provided when vegetation, placed on the nest, began to ferment. Modern crocodiles incubate their eggs in the same way.
Edmontosaurus, another hadrosaur
For more, visit Hoag Levins' exhibit on the discovery of Hadrosaurus foulkii, the first nearly-complete dinosaur skeleton to be discovered.
Original page created by Dave Polly circa 1994, with later modifications by Rob Guralnick, Ben Waggoner and Colleen Whitney; modifications since 2005 by David Smith.
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