Dino of the Week: Scutellosaurus

Type Species: Scutellosaurus lawleri

Classification: Dinosauria – Ornithischia – Thyreophora

Time Period: Early Jurassic

Location: North America

Diet: Herbivore

Scutellosaurus has been a riddle in the ornithischian family tree for a long while. Like its European contemporary Scelidosaurus, it’s been paraded as the kind of dinosaur that could’ve evolved into one of the later, better-known groups of thyreophorans (the armored ankylosaurs and plated stegosaurs). Most scientists consider it a common ancestor of both groups and believe it to be closely related to Scelidosaurus and the later Early Jurassic Emausaurus. Though some want to place it in the Scelidosauridae family along with Scelidosaurus, currently it’s viewed as an earlier, more basal thyreophoran (Scelidosaurus is larger and seems to be a more ‘evolved’ thyreophoran with more similarities to the later ankylosaurs and stegosaurs). 

Scutellosaurus is known from two partial skeletons from Arizona. The remains included portions of the skull and lots of detached bony plates called scutes (from which this dinosaur gets its name). The scutes came in a variety of shapes: some were triangular wedges, others were low cones, some were lopsided trimpets, and still others were curved like horns. Hundreds of detached scutes have been found, but because they were detached, the exact pattern on the body is unknown. Scientists estimate that a single individual had anywhere between two hundred and four hundred of these scutes embedded in its skin like small, raised shields. 

a flock of Scutellosaurus flee a pack of Dilophosaurus

Scutellosaurus was relatively small, growing between four to six and a half feet long, and weighing twenty-fifty pounds despite its light armor. It stood about twenty inches tall at the hips. It was small, slim, and long, and it had an unusually long tail, perhaps to counterbalance the weight of its armor. It probably ran rapidly on all fours since the front limbs had broad, sturdy paws. It could rear up on its longer hind limbs to eat higher plant-stuffs, but it’s unlikely that it could’ve run very well bipedally, since its armor would’ve made it top-heavy. Its mouth had a narrow, beak-like front, and its jaws contained several broad incisors and a row of fluted, leaf-shaped cheek teeth designed to crush plant material. Its head was protected by low bony plates. Scientists speculate that, like the similar-sized heterodontosaurs of the Early Jurassic, this early thyreophoran was gregarious in nature, traveling in ‘family flocks’. 

a Scutellosaurus taking a break with an Early Jurassic turtle