Ankylosauria consists of
groups, Ankylosauridae, Nodosauridae, and Polacanthidae, plus some basal forms. All ankylosaurians
had armor over much of their bodies, mostly scutes and nodules, with large spines in some
cases. The scutes, or plates, are rectangular to oval objects organized in transverse
(side to side) rows, often with keels on the upper surface. Smaller nodules and
plates filled in the open spaces between large plates. In all three groups the first two rows of plates tend to form a sort of half-ring around the
neck; in nodosaurids, this comes from adjacent plates fusing with each other
(and there is a third row as well), while
ankylosaurids usually have the plates fused to the top of another band of bone. The
skull has armor plastered on to it, including a distinctive piece on the outside-rear of
the lower jaw. Feeding was generally accomplished similarly to how Scelidosaurus
did it, with precise
meeting of the teeth leading to a puncture-crush style like a mortar and pestle.
Besides body armor, which is also known lower in Thyreophora, all ankylosaurians (except Mymoorapelta) rewalled the acetabulum (the socket for the femur; it is open in most dinosaurs) for strength and flared the upper surface of the ilium outward. Ankylosaurians were very tubby beasts, suggesting that their somewhat feeble teeth were backed up by an impressive internal digestion system.
Ankylosaurians are a mostly K group from North America and Asia, although isolated finds put them in a number of odd places, including the Campanian (LK) of Antarctica, the late Maastrichtian (LK) and the Toarcian (EJ) of India, and the Campanian-Maastrichtian (LK) of Argentina. Interestingly, ankylosaurians as a group are also the second-most common dinosaurs, next to hadrosaurids, found in marine sediments; this likely is due to their solid construction and (inferred) spacious digestive tracts and other viscera, allowing whole bodies to float out to sea with surprising buoyancy despite the armor.
These classifications of Ankylosauria and Ankylosauridae presented here are very tentative; much new material has been found in recent years, and these classifications will doubtless be altered. For one new look at these armored beasts, see The Tree of Life's ankylosaur pages, and for anyone wishing to read more about armored dinosaurs in general, and who isn't daunted by the technical literature, there is The Armored Dinosaurs, 2001, Kenneth Carpenter (ed), which is where I got much of the material for the reclassifications I've undertaken here.
|Taxon or Taxa:||Time/Place:||Comments:|
|?"Acanthopholis" eucercus (N.D.) Seeley, 1879||late Albian (EK) of England||This animal is doubtfully ankylosaurian.|
|Aletopelta coombsi Ford and Kirkland, 2001||mid Campanian (LK) of "California" (paleo-Mexico)||California's first unique named dinosaur, Aletopelta is based on a partial skeleton, originally thought to belong to a nodosaurid. It was found on a tectonic block that appears to have been rafted north from Mexico, making Aletopelta (whose name means "wandering shield" referring to this change in location) a representative of a heretofore-unknown ankylosaurid radiation, according to the authors. Unlike most ankylosaurids, it had some respectable plates and spines, and the pelvis was covered with locking scutes. It may have been a "stegopeltine" or a traditional ankylosaurid, but nodosaurid is most likely.|
|Antarctopelta oliveroi Salgado and Gasparini, 2006||late Campanian (LK) of Antarctica||First published on in 1991, Anarctopelta becomes the second-named classic dinosaur from Antarctica (well, technically James Ross Island; I don't know if that should count). The skeleton took several years to excavate, what with the frozen ground and all, and consists of part of a dentary, teeth, cranial armor, two cervicals and casts of three others, fragmentary dorsal ribs, a couple of dorsals from the presacral rod, three sacrals, eight caudals, part of a scapula, ilium, and femur, five metapodials, and assorted armor. The owner was about 4 m long, with features of both Nodosauridae and Ankylosauridae.|
|Cryptosaurus eumerus (N.D.) Seeley, 1869||Oxfordian (LJ) of England||Based upon an unusual femur, this animal is better known in the literature as Cryptodraco (a replacement name that turned out to be unnecessary). Cryptosaurus is the true name.|
|Danubiosaurus anceps (N.D.) Bunzel, 1871 (?Struthiosaurus)||early Campanian (LK) of Austria||This is one of a host of indeterminate LK European nodosaurids that may or may not be the same as Struthiosaurus. Alternatively, it could represent one of two nodosaurs from the same formation (the Gosau Beds of Austria): large Danubiosaurus and small Struthiosaurus austriacus.|
|Dracopelta zbyszewskii Galton, 1980||Kimmeridgian (LJ) of Portugal||Dracopelta is one of the better-known early ankylosaurians, based on material including part of a rib cage and some armor in situ.|
|"Hanwulosaurus" (N.N.) Anonymous, 2001||?LK of China||This unofficially-named animal is apparently a very large (~9m long) ankylosaurian, known from many remains including a large flat skull, verts, ribs, scapula, ulna, femora, fibulae, and armor. It may belong to a new clade within Ankylosauria.|
|Hierosaurus sternbergi (N.D.) Wieland, 1909||late Coniacian (LK) of Kansas||Sometimes synonymized with Nodosaurus, this animal is rather late in the fossil record to be so. It is known from armor.|
|"Iguanodon" phillipsii (?N.D.) Seeley, 1869 (Priodontognathus)||Oxfordian (LJ) or EK of England||Better known as Priodontognathus Seeley, 1875, this is a poorly-known early ankylosaurian based on a partial upper jaw. It was once thought to be a stegosaurian. It may be valid, and is not to be confused with the putative stegosaur species "Omosaurus" phillipsii Seeley, 1893, although in this case Seeley went out of his way to make the situation confusing by giving the two the same species name out of the belief that they might turn out to be the same thing.|
|Onychosaurus hungaricus (N.D.) Nopcsa, 1902 (?Struthiosaurus)||Campanian (LK) of Romania||This is an indeterminate ankylosaurian based on armor.|
|Palaeoscincus costatus (N.D.) Leidy, 1856 (?Edmontonia)||late middle Campanian (LK) of Montana and Alberta||Palaeoscincus is a (in)famous ankylosaurian from the early days of American dinosaur paleo based on teeth. At one time, it was commonly restored with a tail club like an ankylosaurine.|
|"Palaeoscincus" asper (N.D.) Lambe, 1902||late middle or early late Campanian (LK) of Alberta||"P." asper is a tooth taxon usually assigned to Euoplocephalus, but all bets are off if Euoplocephalus receives an Iguanodon-like taxonomic dissection.|
|Rhodanosaurus ludgunensis (N.D.) Nopcsa, 1929 (?Struthiosaurus)||Maastrichtian (LK) of France||Based on armor plates, this animal is an obscure indeterminate ankylosaurian, and yes, it may be the same as Struthiosaurus.|
|Sarcolestes leedsi Lydekker, 1893||Callovian (MJ) of England||One of the earliest nodosaurids (?or polacanthid; well, ankylosaurian at any rate), Sarcolestes is based on a jaw once thought to have belonged to a theropod.|
|Sauroplites scutiger (N.D.) Bohlin, 1953||Barremian-early Aptian (EK) of China||Sauroplites may be the same as the better-known Shamosaurus.|
|Stegosaurides excavatus (N.D.) Bohlin, 1953||LK of China||This is just an obscure, indeterminate ankylosaurian.|
|Tatankacephalus cooneyorum W. Parsons and K. Parsons, 2009||late Aptian-early Albian (EK) of Montana||An ankylosaurian from the Cloverly Formation, Tatankacephalus is known from much of a fragmented skull, and potentially rib fragments and a couple of armor pieces. It may have been related to Gastonia, and/or a basal nodosaurid.|
|Tianchiasaurus nedegoatpeferima (?N.D.) Dong, 1993||Bathonian (MJ) of China||This is one of the most basal known ankylosaurians. Its odd species name comes from the cast of Jurassic Park (the name for a while was going to be Jurassosaurus nede...), wherein the first two letters of the last names of the actors were combined. Unfortunately, its remains are rather fragmentary.|
Nodosauridae, Polacanthidae, and Ankylosauridae: Next come the good old nodosaurids, the spiky, nodosaurid-like polacanthids, and the (usually) tail-clubbed, squat-bodied ankylosaurids.
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