hypothesis
... that the hypothesis that the pachycephalosaurian dinosaurs used their domed skulls in head-butting competitions was first proposed in a work of science fiction?
... that the <b id="mwB9M"><a href="./Timeline_of_pachycephalosaur_research" id="mwB9Q" rel="mw:WikiLink" title="Timeline of pachycephalosaur research">hypothesis</a></b> that the <a href="./Pachycephalosauria" id="mwB9U" rel="mw:WikiLink" title="Pachycephalosauria">pachycephalosaurian</a> <a href="./Dinosaur" id="mwB9Y" rel="mw:WikiLink" title="Dinosaur">dinosaurs</a> used their domed skulls in <a href="./Headbutt" id="mwB9c" rel="mw:WikiLink" title="Headbutt">head-butting</a> competitions was first proposed in a work of <a href="./Science_fiction" id="mwB9g" rel="mw:WikiLink" title="Science fiction">science fiction</a>?