 Stegosaurus sulcatus , meaning " furrowed roof lizard " , was described by Marsh in 1887 based on a partial skeleton . It has traditionally been considered a synonym of S. armatus , though more recent studies suggest it is not . S. sulcatus is distinguished mainly by its unusually large , furrowed spikes with very large bases . A spike associated with the type specimen , originally thought to be a tail spike , may in fact come from the shoulder or hip , since its base is much larger than the corresponding tail vertebrae . A review published by Maidment and colleagues in 2008 regarded it as an indeterminate species possibly not even belonging to Stegosaurus at all , but to a different genus . Peter Galton suggested it should be considered a valid species due to its unique spikes . 
