Colored sketch of Troodon formosus, a famous troodontid from the Late Cretaceous of the USA and Canada. It was described from a tooth as a lizard in 1856. Later, the animal was classified as a dinosaur. At one time it was considered a pachycephalosaur: the tooth was assigned to Stegoceras. Charles Sternberg concluded in 1945 that troodon was actually a theropod. A little earlier, a more complete specimen was found in Alberta, named Stenonychosaurus inequalis, to which another partial skeleton was attributed in 1969. For many years, there have been disagreements about the synonymy or separation of these two genera. Recently, Varricchio and colleagues proposed to consider the material from the Two Medicine formation as the neotype of Troodon, and to synonymize Stenonychosaurus with it: https://www.cambridge.org/core/journals/journal-of-paleontology/article/troodontid-specimens-from-the-cretaceous-two-medicine-formation-of-montana-usa-and-the-validity-of-troodon-formosus/3E58F1FDA3FE53DE569E0D0B20E79F22 Troodon was a light, long-legged theropod. Its teeth are distinguished by very large denticles like those of herbivorous reptiles, so perhaps he was an omnivore.
Adobe Photoshop, 2025.
