Dinosaurs from Judith River formation
Hadrosaurs, commonly known as duckbilled dinosaurs, were basically bipedal herbivores, although they probably used their front limbs as legs from time to time as well. Behind their duck-like bill they had a battery of teeth. Each of the 50 or so tooth positions in each jaw was occupied by several teeth at a time, giving them as many as 700 teeth. Of all the dinosaurs it is believed that only hadrosaur had cheeks. Together with their fine teeth, they chewed their food, unlike other dinosaurs which wolfed their food and relied on either gizzard stones (sauropods) or a long digestive tract (ceratopsians) to absorb the nutrients.
Many species had prominent crests on their heads. Skin impressions show that the hands were webbed. The high tail was used for propulsion while swimming, similar to the way an alligator uses its tail.
A dissenting view by some paleontologists holds that since the tail was reinforced by many tendons, it was too stiff to propel the animal in the water.
Most fossils have been found in lowland deposits, but nesting sites have recently been discovered in upland areas, leading to the conclusion that they seasonally migrated.
Hadrosaurs comprise the suborder Hadrosauridae within the ornithischian (bird-hipped) dinosaurs. The arrangement of the hip allowed hadrosaurs to have a large belly for digesting plant material located mainly over their legs, enabling a bipedal posture.
Edmontosaurus is one of the largest, most widespread, and most common of the duckbills. It was the only hadrosaur during the Maastrichten, the latest interval of the Cretaceous.
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Tooth is 9/16" long. Occlusal (chewing) surface is at top. |
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Click image to enlarge. Vertebrae is 2" long. |
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I'm speculating that this may be a skin impression. It was found in close proximity to a Edmontosaurus vertebrae. |
| Formation: | Scollard |
| Epoch: | Maastrichten, late Cretaceous |
| Length: | 43 feet |
| Weight: | 3 tons |
| The name Corythosaurus means helmet lizard for the crest on its head. The crest was larger in the adult males. Corythosaurus may have fed on plants and insect colonies. It preceded the duckbill Edmontosaurus. |  |
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Occlusal surface view of tooth on the left; tooth on the right is unworn, about 3/4" long. The Occlusal surface for the rightmost two teeth is at the top. |
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The lower jaw fragment is probably Corythosaurus. Each groove held several teeth; one groove still holds an unworn tooth. This is the lingual (inside) side of the jaw. |
| Formation: | Oldman |
| Epoch: | Campanian of the late Cretaceous |
| Length: | 33 feet |
| Weight: | 3 tons |
.Kritosaurus
A close relative of Hadrosaurus, Kritosaurus had a flat, broad head, a humped nose, and no crest on top its head.
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Click image to enlarge; the larger vertebrae is 2 1/4" wide. |
| Formation: | Horseshoe Canyon |
| Epoch: | Campanian of the late Cretaceous |
| Length: | 30 feet |
| Weight: | 3 tons |
A close relative of Lambeosaurus, Parasaurolophus had a narrow beak and a long curved crest. Air tubes led through the crest, leading scientists to believe that it was probably used to make bellowing sounds. Some scientists speculate that the narrow beak allowed it to specialize in its diet, nipping off just the desired vegetation.
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Tooth is 5/16" long; occlusal (chewing surface) is at top |
| Formation: | Oldman |
| Epoch: | Campanian of the late Cretaceous |
| Length: | 33 feet |
| Weight: | 2 tons |
Unknown Hadrosaur Species
The following fossils can not be identified according to species.
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Tendons. Tendons are not identifiable to species. It is also possible that these came from a ceratopsian as both hadrosaurs and ceratopsians had a latticework of tendons to support their heavy tails without muscular effort. Tendons are very common fossils in many areas. |
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A hadosaur toe bone; this is an ungual, meaning the end of the toe. |
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A side view of the same toe bone; note the groove that extends areound 3/4 of the bone. |
| Formation: | Oldman |
| Epoch: | Campanian of the late Cretaceous |
| Length: | 33 feet |
| Weight: | 2 tons |