Small Ornithischians

By | September 9, 2016

The dinosaur family tree is split into two halves: saurischians and ornithischians. The ornithischians were plant-eaters with beaked jaws for plucking leaves and large bellies for digesting them. Though some ornithischians were huge, four-footed giants, many were small, two-footed herbivores that scurried about nervously in forests and scrublands, searching for food and trying to avoid predators.


Key features
■ Plant-eaters
■ Beaked jaws
■ Back-pointing pubis bone
■ Large belly for digesting vegetation

Ornithischians lived from the beginning of the Jurassic Period, 200 million years ago, to the end of the Cretaceous Period, 65 million years ago.

Heterodontosaurus (HET-er-oh-DON-toe-SORE-us)


Heterodontosaurus’s complete skeleton was found in 1976 with every bone in place.

When: 200–190 million years ago (Early Jurassic)

Fossil location: S. Africa

Habitat: Scrubland

Length: 3 ft (1 m)

Diet: Plants, tubers, possibly insects

Unlike most dinosaurs, which had one type of tooth, Heterodontosaurus (“different-toothed lizard”) had three types. Its sharp front teeth snipped off tough vegetation, which was then mashed to a pulp with its cheek teeth. It also had large, fanglike teeth to defend itself against enemies. The jaws were tipped with a horny beak that was probably used for plucking leaves.

Hypsilophodon (HIP-sih-LOAF-oh-don)


When: 125–120 million years ago (Early Cretaceous)

Fossil location: England, Spain

Habitat: Forests

Length: 7 ft (2 m)

Diet: Plants

Hypsilophodon was much like a modern deer, grazing on tender plants with its small, leaf-shaped teeth. Fossil footprints grouped together hint that these creatures roamed in herds like deer, though this is far from certain. Its stiff tail and long legs and feet show it was a fast-running ground animal, able to flee swiftly from predators on its hind legs while using its tail for balance.

Leaellynasaura (lee-ELL-in-ah-SORE-ah)


When: 105 million years ago (Early Cretaceous)

Fossil location: Australia

Habitat: Forests

Length: 7 ft (2 m)

Diet: Plants

Leaellynasaura lived near the South Pole. Although it was less cold here during the Cretaceous Period than it is today, Leaellynasaura would have had to live without sunlight for several months of the year during polar winters. It had large eyes, which helped it see better in the dark and avoid predators. It was probably warm-blooded.

Lesothosaurus (li-SUE-too-SORE-us)


When: 200–190 million years ago (Early Jurassic)

Fossil location: S. Africa

Habitat: Desert plains

Length: 3 ft (1 m)

Diet: Leaves, perhaps dead animals and insects

This dinosaur was named after Lesotho, the south African country where its fossils were first found in 1978. Scientists think Lesothosaurus was similar to a modern gazelle, grazing on low-lying plants and running away quickly at the first sight of predators. Its upper and lower teeth were small and shaped like arrowheads.

Othnielosaurus (oth-nee-ELL-oh-SORE-us)


When: 155–145 million years ago (Late Jurassic)

Fossil location: USA

Habitat: Plains

Length: 7 ft (2 m)

Diet: Plants

Othnielosaurus moved swiftly on its strong back limbs, which were built for running. Its front limbs were short and weak, and its hands and fingers were small. Fossils show that its teeth were edged with many small ridges, making them well-suited for shredding leaves. Its vertebrae show that it had a short neck.

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