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TROO - oh - don
Name Means: "Wounding tooth"
The first fossil of Troodon was a single leaf-shaped tooth discovered in 1854 in the Judith River Formation in Alberta, Canada. On the basis of this tooth, Joseph Leidy described and named the animal in 1856. However, Leidy considered Troodon to be a lizard and not a dinosaur. Later discoveries of teeth, from the late Cretaceous of Montana, confirmed Troodon to be a dinosaur. For some time this dinosaur was thought to be a carnivorous ornithopod-its teeth resembled those of some ornithopods-but eventually it was confirmed to be a small birdlike theropod.
Thanks to the discovery of a number of sometimes fragmentary skulls and skeletons, we now know that Troodon had a long snout. However, instead of the row of long, curved teeth that were typical of most theropods, Troodon had a large number of relatively small teeth. Each side of the lower jaw may have had as many as 35 teeth, all of them with large serrations. No other theropod is known to have had so many teeth. The teeth varied in shape, depending on their location in the jaw.
Troodon is famous for the great size of its brain cavity. Troodon and other troodontids may have had the largest brains, relative to body size, of any nonavian theropods. This has led many scientists to conclude that Troodon and its close relatives were more intelligent than other dinosaurs. Such a belief is based on the observation that in living animals there is rough correlation between relative brain size and degrees of intelligence. However, as intelligence leaves no trace in the fossil record, this must remain a matter of speculation. Troodon's very large eye sockets have also led some researchers to believe that it may have been a nocturnal animal.
Recent studies suggest that the troodontids were among the closest extinct relatives of birds. They may also have been very closely related to the dromaeosaurids, such as Deinonychus and Velociraptor. The claw on Troodon's second toe was longer than those on its other toes, but Troodon lacked the long "killer" sickle that characterized the dromaeosaurids.