The Thyreophora ("Shield bearers")
were a subgroup of the ornithischian dinosaurs. They were armored
herbivorous 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.
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The
pictures of thyreophorans are grouped alphabetically on
tabbed pages. |
Thyreophorans 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. In both groups, the forelimbs were much shorter
than the hindlimbs, and this was particularly exaggerated 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 the Cerapoda within the Genasauria.
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.
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 armored
as the ankylosaurids, did 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 are Sauropelta and Edmontonia,
the latter most notable for its formidable forward-pointing shoulder
spikes.
The Stegosauria suborder comprises
the Stegosauridae and Huayangosauridae. These dinosaurs lived
mostly from the Middle to Late Jurassic, although some fossils
have been found in the Early Cretaceous. Stegosaurs had very small
heads; feeble jaws with simple, leaf-like teeth and very small
brains for their body size. Stegosaurs possessed rows of plates
and/or spikes running down the dorsal midline and elongated dorsal
vertebra. It has been suggested that stegosaur plates functioned
in control of body temperature (thermoregulation) and/or were
used as a display to identify members of a species, as well as
to attract mates and intimidate rivals.
