Dinosaurs from Judith River formation
Tyrannosaurids were the largest of the carnivorous dinosaurs, with especially large heads, and robust bodies. The individual species tended to increase in size, culminating in Tyrannosaurus rex at the conclusion of the Cretaceous.
Albertosaurus libratus
A member of the tyrannosaur family, A. libratus shared the Judith River (Alberta) top predator niche with Daspletosaurus torosus. Its main prey was probably the numerous duckbill dinosaurs. It was more lightly built than Daspletosaurus torosus, especially the skull, and had smaller teeth that pointed back more.
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Two Albertosaurus libratus teeth; the larger is 1.3" long. Note the smaller tooth has no enamel; this tooth was probably shed and swallowed; the stomach acids dissolved the enamel. |
| Other name: | Gorgosaurus |
| Family: | Tyrannosauridae |
| Formation: | Oldman |
| Epoch: | Campanian of the late Cretaceous |
| Length: | 28 feet long |
| Weight: | 2.5 ton |
Daspletosaurus torosus
Not as large as later tyrannosaurs, Daspletosaurus was still a fearsome carnivore. Fairly comparable in size to its competitor, Albertosaurus, but more heavily built and less numerous in the Judith River fauna. Duckbills were probably its predominant prey as with Albertosaurus. As it was more robust than Albertosaurus, it may have included the dangerous ceratopsians in its diet as well.
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This
Daspletosaurus torosus tooth is embedded in a Ornithomimus
caudal (tail) vertebrae fragment. The vertebrae fragment is two inches long.
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| Other name: | Tyrannosaurus torosus |
| Family: | Tyrannosauridae |
| Formation: | Dinosaur Park |
| Epoch: | Campanian of the late Cretaceous |
| Length: | 30 feet |
| Weight: | 2.3 ton |
| The vertebrae that the tooth is embedded in is from Ornithomimus, an unusual theropod. While most theropods that had sharp pointy teeth, Ornithomimus had a beak and no teeth. It had unusually long forelimbs and fingers. There is disagreement on its likely diet; it may have been herbivorous or ate small animals like insects. Ornithomimus grew to 12 feet in length with a weight of 300 pounds. |  |
Tyrannosaurus Rex
The largest and last member of the tyrannosaur family, T rex is justifiably famous. It's 3 foot long jaws held about 60 teeth up to 6 inches long. It was much more strongly built than the allosaurs, and at least as fast. Unlike the allosaurs which are thought to have hunted in packs, T rex probably was a solitary hunter. T rex was the only large theropod during the Masstrichten, the latest interval of the Cretaceous.
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This fragment of a Tyrannosaurus Rex tooth was found just like this, embedded in a vertebrae (probably Edmontosaurus). The tooth lies loose. It probably lodged in the non-bony material that was not preserved. The tooth fragment is 1.5" long. |
| Family: | Tyrannosauridae |
| Formation: | Scollard |
| Epoch: | Maastrichten, late Cretaceous |
| Length: | 40 feet |
| Weight: | 7 tons |