Troodon (meaning “wounding tooth;” also spelled Troödon) was a deinonychosaur from the Late Cretaceous period of North America, existing from 75 to 65.5 million years ago. Troodon measured a length of 2.4 meters (7 ft) and was 1 meter (3 ft) tall. Troodon weighed 50 kilograms (110 lb). The meaning of its name refers to a single tooth found at the Judith River Formation by Joseph Leidy in 1856; Leidy consistently spelled the name as Troödon, though the name was changed by Henri Sauvage in 1876 to what it is currently recognized as. Troodon‘s taxonomy was convoluted until 1945; originally, it was classified as a lizard, then revised to being a megalosaurid in 1901 and species of Stegoceras in 1924. Finally, Charles Sternberg concluded that the teeth belonged to more carnivorous dinosaurs upon further examination of the fossils. This moved Troodon and another new dinosaur, Stenonychosaurus, into their own family–called Troodontidae–as well as resulting in the creation of the Pachycephalosauridae family.
In 1969, a more complete Stenonychosaurus skeleton from the Dinosaur Park Formation was described and named by Dale Russel, who speculated that dinosaurs like Stenonychosaurus (and Troodon) may have been intelligent enough to evolve sapience had they not died out, eventually taking on an upright, bipedal form. However, the idea of the “dinosauroid” was rejected by most paleontologists, who suggested that it was “suspiciously human.” Eventually, the teeth were considered a diagnostic feature of the species until 1987, when Phil Currie published a paper regarding that the tooth and jaw structure were based on age and the position of the tooth in the jaw itself. Currie ended up reclassifying Stenonychosaurus inequalis, Polyodontosaurus grandis, and Pectinodon bakkeri as junior synonyms of Troodon. As a result of Currie’s efforts, all specimens of Stenonychosaurus are now considered Troodon.
Troodon itself is known from a few formations, mostly in North America ranging from Alaska to as far south as Texas and New Mexico. Findings of Troodon are mostly concentrated in the Judith River, Lance, Hell Creek, and Two Medicine Formations in Montana, as well as in the Horseshoe Canyon and Prince Creek Formations in Alberta and Alaska. This may indicate that Troodon favored cooler environments.
The teeth of Troodon differ from the majority of theropods because they indicate a possibly omnivorous lifestyle. The jaws and teeth were most similar to that of an iguana, though the teeth were also serrated, implying that they ate meat. Another interesting characteristic is Troodon‘s grasping hands, a large brain, and stereoscopic vision. Ironically, these characteristics can all be compared with primates and raccoons, which are also omnivores. In Alaska, Troodon may well have been an apex predator because of studies regarding their tooth size versus their possible body size. A species of Troodon may have grown exceptionally large due to a lack of competition from tyrannosaurs that were present in the other regions in which it was found. These findings may indicate that Troodon‘s teeth were meant for softer foods.
On Isla Nublar, several Troodon were created by Laura Sorkin and Henry Wu. Troodon was considered to be a security risk because of their complex pack behavior and a deadly venom which they secreted in their mouths. Similar to Komodo dragons, a single Troodon in a pack will rush out and bite a prey animal, and then the pack will linger back, waiting for the effects of the poison to set in: hallucinations, mass sensations of pain, high fevers, paralysis, and eventually brain death. The species cloned by InGen, T. pectinodon, does not exist in the fossil record; it is possible that Dr. Sorkin reclassified them after noticing radical differences from the fossil species due to gene splicing. The Troodon are primarily noctural, and otherwise inhabit very dark environments such as the tunnel systems beneath Isla Nublar. The clicking calls and other noises that the Troodon make, coupled with their large eyes that seem to glow in the dark, gives them a creepy appearance.
Because of the danger they posed, as well as not fitting his vision of what the animals in Jurassic Park should be, John Hammond ordered that the Troodon be destroyed. However, Dr. Sorkin disobeyed this order, and many individual Troodon existed on Isla Nublar because of this, contained in quarantine pens under 24-hour surveillance in the northeastern region of the island. Different groups of Troodon hunted Nima Cruz and mercenaries hired by InGen to extract survivors of the Jurassic Park Incident. They were also observed to have a bizarre nesting behavior: after using their venom to paralyze their prey, the Troodon turn their victims into living nests and lay their eggs in their stomachs, presumably with ovipositors; Dr. Sorkin noted that this behavior was only known otherwise in insects. While this is possible with humans, it is unknown if Troodon made nests out of larger dinosaurs. Due to the self-organizing behavior, high intelligence, and toxic venom of the Troodon, many dinosaurs were fearful of them, even the deadly Velociraptor. It is unknown if Troodon are present on Isla Sorna, as Hammond had ordered their complete extermination, though it is also possible that some Troodon exist–or existed–on Isla Sorna because it was on that island that InGen first engineered its dinosaurs.