| Ankylosaurids Temporal range: 125–65 Ma Jurassic - Cretaceous |
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| Mounted skeleton of Euoplocephalus tutus, Senckenberg Museum | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | Dinosauria |
| Order: | †Ornithischia |
| Node: | †Thyreophoroidea |
| Node: | †Eurypoda |
| Suborder: | †Ankylosauria |
| Family: | †Ankylosauridae Brown, 1908 |
| Genera | |
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See text. |
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| Synonyms | |
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Syrmosauridae Maleev, 1952 |
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An ankylosaurid is a member of the Ankylosauridae family of armored dinosaurs that evolved 125 million years ago (along with another family of ankylosaurs, the Nodosauridae) and became extinct 65 million years ago during the Cretaceous-Tertiary extinction event. Ankylosaurids have been found in western North America, Europe and East Asia, though good specimens are rare; most are known only from bone fragments.
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The heavy armour, forming a veritable shell on the backs of ankylosaurids and their clubbed tails, makes them look superficially similar to the mammalian glyptodonts (and to a lesser degree to the giant meiolaniid turtles of Australia).
Their heavily armoured heads formed a toothless beak at the front (comparable to modern birds), though the sides of the mouth and the lower jaw did bear small teeth, deeply inset from the jaw.
Ankylosaurids usually had a thick armour plating of fused bone, often interspersed with a variety of spikes and lumps. Ankylosaurids were so heavily armored that some advanced species even had armoured eyelids.
Many ankylosaurids also had an enlarged mass of bone forming a "club" on the end of their tails, made of two enlarged bone lumps. This tail club has traditionally been used to separate ankylosaurids from their close relatives the nodosaurids, although the many primitive ankylosaurids ("shamosaurines", and even basal ankylosaurines) also lacked tail clubs.
The polacanthids are sometimes included as a subfamily of ankylosaurids, as Polacanthinae. However, phylogenetic analyses since 2000 have shown the polacanthids to form either a natural group apart from the ankylosaurids, or to be an unnatural grouping of primitive ankylosaurs.[1]
The following uses the ranks from Benton 2004.[2] The following taxonomy follows Thompson et al., 2011 unless otherwise noted.[3]
Ankylosauridae was first named by Brown in 1908 and defined by him as "all ankylosaurs more closely related to Ankylosaurus than to Panoplosaurus". Sereno, 2005 redefined it as: The most inclusive clade containing Ankylosaurus magniventris but not Panoplosaurus mirus.[6] Ankylosaurinae was first named by Nopcsa in 1918 and defined by Sereno, 1998 as "all ankylosaurids more closely related to Ankylosaurus than to Shamosaurus". Sereno, 2005 redefined it as: The most inclusive clade containing Ankylosaurus magniventris but not Gargoyleosaurus parkpinorum, Minmi paravertebra, or Shamosaurus scutatus. The cladogram below follows the most resolved topology from a 2011 analysis by paleontologists Richard S. Thompson, Jolyon C. Parish, Susannah C. R. Maidment and Paul M. Barrett.[3]
| Ankylosauridae |
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