These squat, broad, heavily armoured creatures were equipped with bony plates, studs, and either spikes or a boney tail-club. Despite their amazing protection they were never very common in terms of individuals, although a large number of different species are known.
The Ankylosauria are conventionally divided into two families, the spikey Nodosauridae and the club-tailed Ankylosauridae, but there are are also a few forms that don't fit in either category and would seem to constitute independent evolutionary lineages, like the Australian Minmi.
The teeth are small and weak, indicating a diet of soft vegetation, and the massive limb bones are supported by particularly strong shoulder and pelvic girdles, presumably to carry the weight of the armour.
Ankylosaurian armored scutes are rectangular to oval bony plates organized in rows along the back and tail, giving them the appearance of giant dinosaurian armodillos. Smaller bony nodules fill the spaces between the large plates. The addition of spines and a solid bone tail club in some forms make these squat animals a prickly target for any carnivors.
family Nodosauridae - mid Jurassic to Late Cretaceousfamily Minmiidae - aberrant Gondwanaland formsfamily Ankylosauridae heavily armoured types - mid to late Cretaceous
Sauropelta edwardsi - (drawing copyright © Øyvind M. Padron)
The Nodosaurids appeared as small forms in the Jurassic of Europe, spreading to North America and Asia during the early and mid Cretaceous. They had more extensive armoring then the Scelidosaurs from which they evolved, and often whole patches of external bone were fused into plates. The head was small, equipped with peg-like teeth. Nodosaurids differ from the contemporary Ankylosaurids in the presence of side spines and absense of a tail club.
In contrast to the broad triangular-skulled Ankylosaurids, the elongated snout and relatively narrow beak seems designed for more selective cropping otr browsing. A solid shield of fused keeled plates protected the pelvic area, and are supplemented by flank spines. The limbs are slimmer than those of the Ankylosaurids, and these animals probably could get about faster, even able to use their flank spines to charge and attack preditors. They could also draw in their front legs and crouch down like a tortoise when attacked, with the body close to tehground an dhrad to overturn.
ecological niche: large to very large terrestrial armoured herbivores
chronological range: Middle Jurassic to late Cretaceous
geographical range: Laurasia (Europe, Asia and North America)
This is not, or not yet, an official family, but I thought these distinctive animals deserve a category of their own, to hold a a single species - Minmi paravertebra . They are small long-legged running ankylosaurs from the mid Cretaceous of south-east Gondwanaland. It has unusual structures along its spine, called paravertebrae, whose function and purpose are still unclear, but may have served to strengthen the spine and enable the animal to run rapidly. Their relationship with other ankylosaurs is unclear, but presumably they evolved from Jurassic Nodosaurids. this animal has a mix of ankylosaurid and nodosaurid features, and may well eventually be given its own official family.
Minmi paravertebra Molnar, 1980Horizon:
Comments: see "family" description
The Ankylosaurids are the last of the armoured dinosaurs to evolve. They are distinguished by the heavy club-like tails, presumably used as a defensive weapon against predators, but lack the long spines of teh nodosaurs. The primitive Polacanthine group was originally included under the nodosauridae. They only had small tail clubs.
The skull is heavy and re-inforced, and in contrast to the Nodosaurids wider and triangular with small horns at upper and lower corners and a mosaic of small armour plates over the skull. The beaks is also wider, indicating a non-selective grazing or cropping of low vegetation, so it is clear that tehse animals had different feeding strategies to the contemporary nodosaurs.
In all ankylosaurids the armour is arranged in transverse bands of bony plates along the neck, back and tail.
Really, Really Fat Ankylosaur - Gregory Paul suggests Ankylosaurids
were even fatter then previously thought
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page historypage uploaded 12 May 1999