 In 1849 , a few years before his death in 1852 , Mantell realised that iguanodonts were not heavy , <unk> @-@ like animals , as Owen was putting forward , but had slender forelimbs ; however , his passing left him unable to participate in the creation of the Crystal Palace dinosaur sculptures , and so Owen 's vision of the dinosaurs became that seen by the public for decades . With Benjamin <unk> Hawkins , he had nearly two dozen lifesize sculptures of various prehistoric animals built out of concrete sculpted over a steel and brick framework ; two iguanodonts ( based on the Mantellodon specimen ) , one standing and one resting on its belly , were included . Before the sculpture of the standing <unk> was completed , he held a banquet for twenty inside it . 
