Thyreophora

Thyreophorans Temporal range: Early Jurassic-Late Cretaceous, 199.6–66 Ma PreЄ Є O S D C P T J K Pg N
Mounted skeleton of Mymoorapelta maysi, Makuhari Messe
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Order:	†Ornithischia
Clade:	†Genasauria
Clade:	†Thyreophora Nopcsa, 1915
Subgroups
†Emausaurus †Scutellosaurus †Tatisaurus? †Thyreophoroidea †Scelidosauridae †Eurypoda †Ankylosauria †Stegosauria

The Thyreophora ("shield bearers", often known simply as "armored dinosaurs" - Greek: θυρεος, a large oblong shield, like a door and φορεω, I carry) were a subgroup of the ornithischian dinosaurs. They were armored dinosaurs, living from the early Jurassic until the end of the Cretaceous.

Thyreophorans are characterized by the presence of body armor lined up in longitudinal rows along the body. Primitive forms had simple, low, keeled scutes or osteoderms, whereas more derived forms developed more elaborate structures including spikes and plates. Most thyreophorans had relatively small brains for their body size.

Thyreophorans include various subgroups, including the suborders Ankylosauria and Stegosauria. In both the suborders, the forelimbs were much shorter than the hindlimbs, particularly in stegosaurs. The clade has been defined as the group consisting of all species more closely related to Ankylosaurus than to Triceratops. Thyreophora is the sister group of Cerapoda within Genasauria.

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 best-known ankylosaurid.

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