Hadrosaursby Neal Immega, Paleontologist and Master DocentWritten in 2003 for use in the Paleo Hall documentationSubmitted by Neal Immega for use on the HMNS Volunteer Website on 3/11/08

Our museum has its hadrosaurs as part of a herd with a juvenile following an adult, a perfectly reasonable setting. There is good evidence that at least some types of hadrosaurs were caring parents who fed their young in a nest until the nestlings had grown to a yard from nose to tail. This nurturing may explain why Hadrosaurs fossils are quite abundant. Our specimens are composites, assembled from a jumble of bones found in a Cretaceous sandbar. Note that some of the leg bones are crushed.

Adult hadrosaur.

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Juvenal hadrosaur.

Name: Hadrosaur means “bulky lizard”, another example of a name that is not very diagnostic. These animals are also known as duckbill dinosaurs, for their broad beak. Edmontosaurus, the genus name, points to Edmonton, Alberta, where the first of these animals was found in 1917.

Diet: The very best data about hadrosaurs come from specimens where an animal was mummified before being buried. Some of these fossils retain the structure of the soft parts and preserve stomach contents. A new hadrosaur find from the Judith River Formation in Montana, a Brachylophosaurus called “Leonardo”, preserved stomach contents of conifers and ferns. This is a very surprising diet because almost no modern animal eats these. Cattle and buffalo commonly abort their fetuses if they eat pine needles when snow has covered all other forage. Ferns, particularly uncooked, are also toxic. The “live off the land” books tell people to eat only the well-cooked young shoots (called fiddleheads for their shape) and to avoid the toxic older fronds. There are many studies on cattle, which suffer after eating fern foliage. Hogs, however, regularly devastate tracts of Australian tree ferns by eating their starchy centers and seem to survive quite well. There is frequently a specific predator for a plant, no matter how toxic (e.g. Monarch caterpillars feed on highly toxic milkweed plants.). The energy cost to safely digest a toxin is repaid by having exclusive access to a food supply that is poisonous to other animals. Maybe hadrosaurs were the same. They were certainly abundant in the Cretaceous.

Beak: Hadrosaurs had a keratin-covered beak in the front that could be used to nip off vegetation and teeth in the back to chop it up. This is the same arrangement as the ceratopsians like Triceratops. Our specimens do not show the actual beak, just its core. The full beak (preserved in some specimens) would have been about 3 inches longer and two inches wider.

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Hadrosaur skull showing teeth recessed from the edge of the skull.

Teeth: Hadrosaurs had rear teeth that cut like a pair of scissors. Multiple rows of leaf-shaped teeth on the upper and lower jaws slid past each other vertically in a self-sharpening arrangement. As in other dinosaurs, these teeth were continually replaced. The jaw hinge allowed only an up-and-down motion.

Cheeks: Hadrosaurs have cheeks! The next time you eat a carrot, notice that you chew it into your cheek and then back out. The Hadrosaur did the same. The tooth battery is recessed from the edge of the jaw to have a pocket to chew things into.

Skull: Modern reptiles grow continuously and dinosaurs likely did the same. To accommodate this, the skull is made of separate plates. You can see this particularly well in the skull of Triceratops. From the muscle scars, it is likely that the whole head moved when the animal chewed. That’s using your head! Unfortunately, the plates were easily separated when the bones were transported by rivers and, thus, complete skulls are scarce and expensive.

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Noises: If you watched all the Jurassic Parks, then one of the animals you saw was a hadrosaur that made loud, honking sounds. Some hadrosaur species had a folded resonating chamber as a crest on their heads, like a bassoon. Our skeletons are from a species that did not have such an elaborate nasal arrangement.

Brain: Lets be tactful and not dwell out the shortcomings of dinosaurs in brain development. It would be particularly difficult to fit in Dinotopia-style language and writing skills in a brain the size of the thumb of a 4th grader. Any student has more brains than a herd of dinosaurs but, to be fair, the dinosaurs did not waste any power on English and Social Studies (children like this comparison).

Feet: The venerable skeleton of a Triceratops in the Smithsonian was put together using Hadrosaur feet! Oops. Just think how difficult it is to put a jumble of bones back together. The Leonardo mummy (remember, it is a different species than ours) has bigger leg/foot “scales” (tubercules) than on the body, a “mitten” of skin that encloses the fingers, and indications of a pad under the foot.

Nests: John Horner (Museum of the Rockies) found a nesting ground in Montana with the nest on about a 25-foot grid. Maybe hadrosaur colonies were like some birds, which squabble with their neighbors if the nest spacing is closer than the size of an adult. Horner named these Maiasaura, which translates into “Good Mother Lizard” because he found good evidence that the kids were kept in the nest until they had grown a bit. He found fragmented, trampled egg shells in nests, suggesting that the young stayed in the nest until the bottom had been stomped flat. More evidence comes from the soft ends of the nestlings’ bones, a juvenile trait very similar to that of modern babies that do not need to get up and run within a few hours of getting born. Our museum has a nest (from France) of an unknown dinosaur that apparently did not keep the young in the nest because the eggshells are intact except for the area on top, presumably where the hatchling crawled out. The nests that Horner found are scrapes in the mud about 5 feet in diameter and 3 feet deep. Fortunately (for science but not the mother hadrosaur), a flood filled the red mudstone of the nest with green mudstone, and the filling was gentle enough to retain lots of hatchling skeletons. The color contrast helped greatly in making sense of the nest configuration.

Family: The fossil evidence shows that at least some species of hadrosaur traveled in family groups. Death assemblages have individuals with large crests (male?) and no crests (female?) and lots of smaller ones from 3 feet to 10 feet from nose to tail (juveniles?). The species of Edmontosaurus that we have does not seem to have enough sexual dimorphism that would let us determine if the family groups had males and females present.

First Mounted Skeleton: We always think of dinosaurs roaming around the northern Great Plains, but one of our docents (Greg Sarto) was quick to point out that the very first mounted skeleton in the world was a duckbill from New Jersey. Will Foulke was what we would today call a rockhound. He had heard about an old discovery of huge bones in a marl pit and decided that he must dig them out. He, along with a gang of hired diggers, spent the summer of 1858

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excavating. In England, in 1841, Richard Owen had described dinosaurs from scraps and, now, there was a complete skeleton. In one step, dinosaurs went from an academic subject to a public sensation!

The locality was lost until a 13-year-old boy scout, Chris Brees, made it his project to find and mark the site. Now the local garden club keeps it up. Way to go!

Photographs were taken in the Houston Museum of Natural Science Mineral Hall by the author

If you want to learn more:

“Leonardo” the mummy - http://www.montanadinosaurdigs.com and http://news.nationalgeographic.com/news/2002/10/1010_021010_dinomummy.html

John Horner, 1990, Digging Dinosaurs, 210 pages, Harper and Row publishers.

New Jersey hadrosaur - http://www.levins.com/dinosaur.shtml and - http://home.earthlink.net/~skurth/DINO.HTM

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