 Compared to "Iguanodon bernissartensis", "Mantellisaurus " was smaller, estimated at in weight.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".