Hayden explored what would later become known as the Judith River Formation, a large area of sedimentary materials deposited in the lowland areas bordering the Colorado Sea during the Late Cretaceous Period 78 to 74 million years ago. Here, Hayden’s party recovered a small collection of teeth which were later described (in 1856) by Joseph Leidy at the Academy of Natural Sciences in Philadelphia. Three of the specimens described were dinosaurs – Trachodon, Troodon (now known as Stegosaurus), and Deinodon (notice the use of ‘don’ meaning ‘tooth’). This was the first published description of dinosaur remains in the United States. Leidy recognised that Trachodon was a creature similar to Iguanodon.
Interestingly, for centuries the Blackfeet have inhabited the high plains of Montana and Alberta – the same area in which the dinosaur-rich, Late Cretaceous Hell Creek and Oldman Formations occur. Dinosaur fossils were known to the Blackfeet, who considered them to be the remains of giant, ancestral buffalo. The Blackfeet used dinosaur bones in rituals intended to insure good hunting. Notwithstanding the religious significance dinosaur bones had for the Blackfeet, they were quite enlightened in their view toward dinosaurs. They hit on the antiquity, and the organic nature of dinosaur remains, and in comparing them to buffalo showed their sophisticated knowledge of vertebrate anatomy. Referring to dinosaurs as large buffalo was thus good scientific practice in the context of their perception of the natural world. In doing this, they were as close to the truth as was the Rev. Dr. Plot back in England, or any other European of the time.