 Stegosaurus armatus , meaning " armored roof lizard " , was the first species to be found and the original type species named by O.C. Marsh in 1877 . It is known from a partial skeletons , and more than 30 fragmentary specimens have been referred to it . However , the type specimen was very fragmentary , consisting only of a partial tail , hips , and leg , parts of some back vertebrae , and a single fragmentary plate ( the presence of which was used to give the animal its name ) . No other plates or spikes were found , and the entire front half of the animal appears not to have been preserved . Because the type specimen is very fragmentary , it is extremely difficult to compare it with other species based on better specimens , and it is now generally considered to be a nomen dubium . Because of this , it was replaced by S. stenops as the type species of Stegosaurus in a ruling of the ICZN in 2013 . 
