Iguanodons

Plant-eating Iguanodons were large dinosaurs capable of walking on two legs or on all four. Their outstanding feature was a highly specialised, five-fingered hand made up of an erect and spiked thumb used for defence or perhaps foraging, three middle fingers and a grasping fifth finger. Iguanodons were one of the first dinosaurs ever described and artistic impressions have changed much with each new discovery. Currently, it's thought they held the head low to the ground and their long, heavy tail in the air for balance rather than vice versa. Herds of Iguanodon - the different species varying in size - flourished in Europe and North America during the lower Cretaceous period.