Mantellisaurus was a lightly constructed iguanodont. Compared to Iguanodon bernissartensis, Mantellisaurus was smaller. Its forelimbs were proportionally shorter than those of I. bernissartensis. In Mantellisaurus the forelimbs were about half the length of the hindlimbs whereas they were about 70 percent the length of the hindlimbs in I. bernissartensis. Due to the short length of its forelimbs and the shortness of its body, it was primarily bipedal, only going on all fours when standing still or moving slowly. As the Iguanodon, he uses his thumbs to defend itself against its predators, as Neovenator, or for that fight when two males that fight.
He made an appearance in "dinosaurs britain".