stegosaurians

Stegosaurians are a group of herbivorous armored dinosaurs within the larger clade Thyreophora. They are best known for a row of large, flat plates along the back and a tail armed with spikes. The most famous member is Stegosaurus, but other genera include Kentrosaurus, Huayangosaurus, Dacentrurus, and Miragaia.

They lived during the Middle to Late Jurassic period, roughly 165 to 150 million years ago. Fossils have been found in North America, Europe, and Asia, with additional forms described from Africa. Stegosaurians are part of the broader diversification of plated and armored dinosaurs that also includes the ankylosaurs.

In anatomy, stegosaurians were mid-sized to large, quadrupedal herbivores with relatively small heads and beaked mouths. Their hind limbs were typically longer than their forelimbs, giving a slightly arched posture. The back plates, which could be upright or tilted, varied among genera. The tail bore slender osteoderms or spikes, used for defense. The function of the plates is debated; proposed roles include display for species recognition and thermoregulation, while the tail spines provided a means of defense.

Classification places Stegosauria within Stegosauridae for the more derived plate-bearing members and includes basal groups such as Huayangosauridae. The name Stegosaurus means “roof lizard,” referencing the distinctive back plates. Stegosaurians declined by the Late Jurassic, with only a few late-surviving forms known from the fossil record.