WordNet (r) 3.0 (2006):

suborder Ornithopoda
    n 1: widespread group including duck-billed dinosaurs and their
         early relatives (hadrosaurs, trachodon and iguanodon) [syn:
         Euronithopoda, suborder Euronithopoda, euronithopod,
         Ornithopoda, suborder Ornithopoda]