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Ankylosauria are known from all continents except
|The family Nodosauridae, or “node lizards”, were more primitive than the family Ankylosauridae and lack a tail club. They possessed bands of bony plates, spines, and nodules along their backs. The earliest known nodosaur, Sarcolestes, is dated from the Mid-Jurassic (Czerkas, 1990). Hylaeosaurus (perhaps the same genus as Polacanthus) had curved spines on neck and shoulders. Their eyes were located more posteriorly; this is an adaptation for spotting predators often seen in animals which browse low to the ground. Higher nodosaurs evolved in the Early Cretaceous. Acanthopholis was 3-4 meters long and Struthiosaurus was 2-3 meters long. Edmontonia (see image above) had spikes on shoulders which might have been used for lunging at attackers. Edmontonia also had bigger shoulder plates than other nodosaurs; the bone of these armor plates was probably covered by horn in life. Nodosaurus is actually poorly known and might be an ankylosaur instead of a nodosaur. Of the 2 great groups of nodosaurs, one (Panoplosaurinae) had squat snouts and lumpy armor while the other (Edmontoninae) had flat armor and unswollen snouts (Bakker, 1988)|
|The family Ankylosauridae, or “fused lizards”, possessed fused back vertebrae. Most of the derived features of this group involve their armor. Although the elements of the armor are present in fossils, often the exact arrangement of spikes and spines on living organisms is unknown. At least some had bands of hollow armor plates across back and tail. The plates in skull were firmly attached to skull bones and the various fenestrae in the skull were closed. Lateral spikes projected from the back of skull, known as squamosal horns. Some had horn-covered bony plates projecting from back and shoulders (Lambert, 1990, Fastovsky, 1996).|
|The last tail vertebrae were fused in a terminal tail club with 4 additional bony plates, 2 large and 2 small.|
|Ankylosaurs possessed a unique folding of their nasal passages, unlike nodosaurs.|
The number of metarsals and phalanges in the feet varied among ankylosaurs.
(Weishampel, p. 473)
have evolved in the Upper Jurassic in
| Are the ankylosaurs and nodosaurs the only
2 groups of Ankylosauria? One animal
may be an ankylosaur, a nodosaur, or perhaps a member of a third group of
armored dinosaurs. It had small armor
bones on its underside and each vertebra had a plate called a paravertebrae
and bony rods for reinforcement.