The very first dinosaur fossil was a thigh bone found in the year 1787 by Dr. Caspar Wistar in the US. The study of Dryosaurus fossils gives us an image of the dinosaur and also tells us a lot about the Dryosaurus Characteristics.In early 19th Century, fossils found were formally recognized as the dinosaurs. Fossils of Dryosaurus include : Many fossils have found.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 Dryosaurus lived is Jurassic and was present 155 - 145 million years ago. Dryosaurus discovery is credited to Othniel Marsh. It was named and described in the year 1894-01-01 (1894).