 S. stenops had four dermal spikes , each about 60 – 90 cm ( 2 @.@ 0 – 3 @.@ 0 ft ) long . Discoveries of articulated stegosaur armor show , at least in some species , these spikes protruded horizontally from the tail , not vertically as is often depicted . Initially , Marsh described S. ungulatus as having eight spikes in its tail , unlike S. stenops . However , recent research re @-@ examined this and concluded this species also had four . 
