"spinostropheus" was a relatively small theropod. in 2010, gregory s. paul estimated its length at 4 metres (13 feet), and its weight at 200 kg (441 lbs). in 2012 thomas r. holtz jr gave a length of 6.2 meters (20.3 feet). in 2016 molina-pérez & larramendi gave a higher estimation of 8.5 meters (28 feet) and 600 kg (1.323 lbs) for the mnhn specimen known from an ulna.