Name means: Bird Thief
Range: Late Jurassic (Kimmeridgian, 156-151 MYA) from Wyoming, possibly Colorado
Size estimate: 5-6 ft length, 30-35 lbs
Discovery: Henry Fairfield Osborn, 1903
Classification: dinosauria, saurischia, therapoda, coelurosauria, compsognathidae
Known only from an incomplete skeleton with a badly crushed skull, Ornitholestes presents several puzzles to scientists. Some of these mysteries have inspired conflicting theories. Others have led to myths in popular folklore. For many years, it was the only small carnivore known to scientists from its area and time period. As a result, dozens of isolated bones from other quarries have been referred to Ornitholestes, but not always for clear reasons. Yet enough good evidence comes from its skeleton to give scientists a good idea of its appearance and habits.
The head of Ornitholestes was proportionally smaller than other theropods, and it had unusually large eyes. Its long arms had a wide range of motion. Due to its size, scientists and enthusiasts alike have assumed it could run quickly. Recent reconstructions of its legs indicate they were too short for it to have relied much on speed. Details of its torso, backbone, and legs suggest a more flexible, agile creature instead. Together these details imply an ambush predator that caught small prey with its hands before inflicting a killing bite. It may have had good vision in low light, in forested areas or at night. The size of its eyes may also show that it relied mostly on its vision when hunting.
Some depictions of Ornitholestes, like the sculpture displayed here, include a horn or crest on its nose. As the fossilization process crushed its skull, it also distorted some of the bones. One of the broken nasal bones twisted enough to suggest a possible crest. Further examination supports the absence of a crest. Such confusion has led to a number of conflicting classifications for this animal. The crest misled some scientists to group it with Proceratosaurus, an early member of the tyrannosaur family known for its nasal crest. Its flexible arms have led some to group it with the maniraptors. This group includes animals like Oviraptor, Deinonychus, and Troodon. The most recent studies classify it with the chicken-sized Compsognathus. More Ornitholestes fossils or new discoveries of related animals will help clarify its relationships.