Thyreophora

The Thyreophora (Shield Bearers) are a subgroup of the ornithischian dinosaurs They were armored herbivorous dinosaurs, living from the early Jurassic until the end of the Cretaceous.

The Thyreophora include well-known suborders such as the Ankylosauria and Stegosauria as well as lesser known groups. Among the Ankylosauria, the two main groups are the Ankylosaurids and Nodosaurids.

Ankylosaurids are noted by the presence of a large tail club composed of distended vertebrae that have fused into a single mass. They were heavy-set and heavily armored from head to tail in bony armor, even down to minor features such as the eyelids. Spikes and nodules, often of horn, were set into the armor. The head was flat, stocky, with little or no "neck", roughly shovel-shaped and characterized by two spikes on either side of the head approximately where the ears and cheeks were. Euoplocephalus tutus is perhaps the most well-known Ankylosaurid.

Nodosaurids, the other family in the Ankylosauria, may actually include the ancestors of the ankylosaurids. They lived during the middle Jurassic (approx 170 mya) on up through the late Cretaceous (65 mya) and, while equally armored as the ankylosaurids, do not have a tail club.
Instead, the bony bumps and spikes that covered the rest of their body continued out to the tail and/or were augmented with sharp spines. Two examples of Nodosaurs would be the specimens Sauropelta and Edmontonia rugosidens, the latter most notable for its formidable forward-pointing shoulder spikes several feet in length.

The Stegosauria are comprised of the Stegosauridae and Huayangosauridae and lived mostly from the Middle to Late Jurassic, although some fossils have been found in the Early Cretaceous.