A smaller herbivore, Hypsilophodon (meaning Hypsilophus Tooth, Hypsilophus being an early name for an iguana species) feeds primarily on fresh growth and roots. It is a bipedal species, although it often is seen bending forward using its tail for balance and digging for roots with its forehands and toothy beak.

Characteristic traits of Hypsilophodon include an opposable fifth digit on each hand, and a stiff, near immobile tail. Their proportionately large triangular head has large eyes. They are built for running, and despite their size can be a challenge for carnivores to catch.