In this lesson we will discuss Thyrephora, which are the four-legged armored herbivores from the Jurassic and Cretaceous periods. These extinct reptiles are ancestors of birds.
The knights in shining armor of the dinosaur world are the Thyreophora. Thyreophora (also called ‘longshield bearers’) are herbivores from the order Ornithischia. Ornithipods are land-based reptiles with hips similar to that of a bird.
They are identified by their osteoderms, or bony plates or spikes which form an armor that protects them from predators. Although most ornithipods lived in herds, Thyreophora appear to be an exception. Bones of Thyreophora are rarely found in groups. Let’s examine some examples of Thyreophora.
The Scutellosaurus (little shield lizard) is the first know Thyreophoran. This dinosaur lived in western North America during the Jurassic period about 200 million years ago.
It is known for being small, only about 1.5 meters long and 22 pounds, and having a slender tail. The Scutellosaurus had small armored plates on its back. This early Thyreophoran was bipedal, meaning it primarily walked on two legs, although it could also walk on four legs.
The Scelidosaurus (limbed lizard) lived in western Europe about 180 million years ago. It was significantly larger than the Scutellosaurus at about four meters long and one meter tall, and it weighed roughly 500 pounds.
Rather than plates, it had spikes on its back and claws similar to hoofs. Heavier armor meant that Threophorans from this point forward became quadrupeds, meaning they walked on four legs.
The Stegosaurus (shingled lizard) is one of the better known Thyreophorans. It had two rows of plates and spikes along its back and tail that suggests it was actively defensive against predators. Early Stegosaurs were 2.
5-3 meters long, but they eventually grew to around 9 meters in length and weighed about 3 tons. They lived all across the world about 150 million years ago. Although they were quadrupeds, they may have been able to pull up on their hind legs to feed from trees.
The Ankylosaurus (fused lizard) lived in the Cretaceous period, which was about 65-145 million years ago.
This dinosaur was 7-10 meters long and weighed 3-4 tons. The Ankylosaurus was heavily armored with patches of bone plates on its back, spikes on the back of its head, and a clubbed tail that was used to passively defend itself from predators. In some cases the osteoderm of the ankylosaurus has been found to also cover the underbelly, legs, and face. Their strong tongues indicate that these dinosaurs may have eaten insects as well as plants.
Thyreophora are terrestrial ornithopods from the Jurassic and Cretaceous periods.
They are primarily herbivores, although the ankylosaurus may have eaten insects as well. Generally, Thyreophora are thought to be quadrupeds, but the earliest Thyreophoran, the scutellosaurus, was able to walk on two or four legs. These dinosaurs are best known for their osteoderms, which created an armor to protect these dinosaurs. While the stegosaurus is thought to have been actively defensive, the ankylosaurus was more likely passively defensive.
Unlike other ornithopods, Thyreophorans did not live in herds. Over time, these dinosaurs became progressively larger, appearing in the following order all over the world: scutellosaurus, scelidosaurus, stegosaurus, and ankylosaurus.