 The earlier and more basal genus Huayangosaurus from the Middle Jurassic of China ( some 165 million years ago – Mya ) <unk> Stegosaurus by 20 million years and is the only genus in the family Huayangosauridae . Earlier still is Scelidosaurus , from Early Jurassic England , which lived about 190 Mya . Interestingly , it possessed features of both stegosaurs and ankylosaurs . <unk> from Germany was another small quadruped , while Scutellosaurus from Arizona was an even earlier genus and was facultatively bipedal . These small , lightly armored dinosaurs were closely related to the direct ancestor of both stegosaurs and ankylosaurs . A trackway of a possible early armored dinosaur , from around 195 Mya , has been found in France . 
