The very first dinosaur fossil was a thigh bone found in the year 1787 by Dr. Caspar Wistar in the US. The study of Aachenosaurus fossils gives us an image of the dinosaur and also tells us a lot about the Aachenosaurus Characteristics.In early 19th Century, fossils found were formally recognized as the dinosaurs. The dinosaurs first came into existence in the Triassic period of the Mesozoic era which was about 248 to 65 million years ago. The time period in which Aachenosaurus lived is Late Cretaceous and was present 84 million years ago. Aachenosaurus discovery is credited to Gerard Smets. It was named and described in the year 1888-01-01 (1888).