Othnielia (oth-ni-ee-lee-a) was an ornithopod dinosaur that measured about 4 ft (1.1 metres) long, weighing about 50 pounds (22.5 kg).

Othnielia had a horny beak and a small skull with self-sharpening cheek teeth. Othnielia may have had cheek pouches.

This plant eater was bipedal (walked on two legs). It had thin legs and a stiffened tail that gave it speed and agility.

It had five-fingered hands and four-toed feet, all clawed. It had large eyes and short arms. Othnielia resembled Hypsilophodon (but had longer feet and different vertebrae).

Othnielia was a very fast bipedal (two-legged) runner. It had long legs with very long shins; this made it a very fast runner. Running was its primary defence predators. Othnielia had a stiffened tail that helped it balance when running and turning.

Othnielia lived during the late Jurassic Period, about 156-145 million years ago.

Othnielia may have lived in herds They probably laid eggs and may have cared for their young.

Othnielia was an ornithopod, whose intelligence (as measured by its relative brain to body weight, or EQ) was midway among the dinosaurs.