Ankylosauridae

   Ankylosaurids, even more than their nodosaurid and polacanthid cousins, epitomize the idea of "dinosaurian tanks."  They were wide animals, covered in armor, and often have large bony clubs at the end of their tails.  Unlike nodosaurids and polacanthids, most ankylosaurids did not have large spikes or spines, but rather concentrated on scutes and ossicles (essentially little scutes).
       Ankylosauridae is made up of two main groups.  Possibly basal Shamosaurinae is composed of long-headed relatives to Ankylosaurinae.  Ankylosaurines had short, wide skulls and large tail clubs composed of two lateral enlarged dermal bones and a terminal dermal bone. Both ankylosaurines and shamosaurines are known to have had convoluted sinus passages in their skulls, possibly for a variety of reasons including improving the sense of smell, making loud sounds, and warming the air inhaled.  They also had large pyramid-shaped "horns" the the top and bottom corners of the back of the skull.  Ankylosaurids with clubbed tails had stiffened tails and less armor along the tail than their clubless counterparts.  The club could not move up or down too far, and its lateral movement was also limited, but not to the same degree; nevertheless, it was at a good height to injure theropod metatarsals through simple blunt trauma.
    Good ankylosaurid remains first show up in late Early Cretaceous Asia with Shamosaurus, and the group apparently quickly spread to North America (Cedarpelta) near the EK-LK boundary, along with other groups with an Asian-European start like hadrosaurids, tyrannosaurids, therizinosaurians, and ceratopians.  Also like these groups, while becoming well-established in the northern continents, the ankylosaurids do not appear to have made big inroads into Gondwanaland (although occasional reports from South America, Antarctica, Africa, and India show nodosaurids dispersed there, but were never particularly common); it may be that the Gondwana continents had spread too far from the northern continents by the middle of the Cretaceous that dispersal between the two great zones couldn't occur.  This may have broken down by the end of the Cretaceous; see the relative success of hadrosaurids in South America.    

<--Ankylosauridae
      |--Cedarpelta
      `-+--?Shamosaurinae
          |     `--Shamosaurus
          `--Ankylosaurinae
               |--Ankylosaurus
               `--+--Saichania
                    `--+--Tarchia
                         `--+--Talarurus
                              `--+--Euoplocephalus
                                   `--Pinacosaurus

Ankylosauridae:

Taxon or Taxa: Time\Place: Comments:
Cedarpelta bilbeyhallorum Carpenter, Kirkland, Burge, and Bird, 2001 late Albian-early Cenomanian (EK-LK) of Utah This was a large basal ankylosaurid.  It is based on a partial skull and known from partial remains from several individuals from the upper Cedar Mountain Formation.  The skull horns were not as large as later ankylosaurids displayed, and the snout was unusually narrow and had premaxillary teeth.  Earlier reports had called this creature "Bilbeyhallorum".

Ankylosauridae i.s.:

Taxon or Taxa: Time\Place: Comments:
Bissektipelta archibaldi Parish, Jolyon, and Barrett, 2004 (originally Amtosaurus archibaldi Averianov, 2002) late Turonian-?Coniacian (LK) of Uzbekistan First assigned to Amtosaurus, here considered a synonym of Talarurus, this new species is known from a braincase.  As far as I know, it is Uzbekistan's first named ankylosaurian.
Glyptodontopelta mimus (?N.D.) Ford, 2000 ?late Maastrichtian (LK) of New Mexico Based on several scutes, this animal was referred to the new possible subfamily Stegopeltinae, but could be a shamosaurine instead.  As more information on this interestingly-named (based on the mammalian glyptodonts, often described as giant armadillos) ankylosaurid is released, it will be posted.
Nodocephalosaurus kirtlandensis Sullivan, 1999 early late Campanian (LK) of New Mexico This new ankylosaurid, based on a partial skull, may be close to the roughly contemporaneous Saichania and Tarchia.  It is mostly interesting at this point as an example of the incompletely-known New Mexican late Cretaceous fauna.
Tianzhenosaurus youngi Pang and Cheng, 1998 (?including Shanxia tianzhenensis Barrett, You, Upchurch, and Burton, 1998) (?Saichania) Campanian (LK) of China Tianzhenosaurus is one of several new Asian ankylosaurids.  It is apparently the same as Shanxia, known from a partial skull and postcranium from a rather basal ankylosaurid.  The skull, much wider than tall, shows long, slender squamosal horns.  Priority is somewhat uncertain, but it may not matter, because they could both be the same as Saichania.

Shamosaurinae:

Taxon or Taxa: Time\Place: Comments:
Shamosaurus scutatus Tumanova, 1983 Barremian-early Aptian (EK) of Mongolia Shamosaurus is a basal ankylosaurid known from remains pertaining to several individuals, including a good skull with a narrow beak and small horns like Cedarpelta.  It is usually assumed to have had a tail club, but this part of its anatomy has never been discovered (indeed, apparently nobody has ever really gotten around to describing the referred postcranial material).

Shamosaurinae i.s.:

Taxon or Taxa: Time\Place: Comments:
Gobisaurus domoculus Vickaryous, Russell, Currie, and Zhao, 2001 Aptian-?Albian (EK) of China Based on a nearly complete specimen, found in 1959 or 1960 (inspiring a specific name roughly meaning "overlooked," recalling the "neglected marvelous lizard" Thescelosaurus), Gobisaurus is described as close to Shamosaurus.
?Tsagantegia longicranialis Tumanova, 1994 ?Santonian (LK) of Mongolia Tsagantegia may be a shamosaurine or a basal ankylosaurine.  It had a long, very flat, smooth skull and small horns, but a wider snout that Shamosaurus or Cedarpelta.

Ankylosaurinae:  Ankylosaurine skull are very distinctive in dorsal or ventral view; they resemble short, fat Ts.

Taxon or Taxa: Time\Place: Comments:
Ankylosaurus magniventris Brown, 1908 late Maastrichtian (LK) of Montana, Wyoming, and Alberta Ankylosaurus was a rare, large (c. 6-7 m long) Lancian ankylosaurine with very prominent "horns".  It is known from three substantial specimens including good skulls, but oddly has never received much attention.  It is traditionally depicted with a regular checkerboard of oval scutes over the back and a fringe of short lateral conical spikes, an embellishment based on Edmontonia (you see, it was only in the '70s that ankylosaurians were separated into nodosaurids and ankylosaurids, so in older restorations it is not uncommon to see "Palaeoscincus" wandering about with a fat tail club and armor based on Edmontonia; Edmontonia, more often than not called Palaeoscincus, being the only ankylosaurian besides "Scolosaurus" with decent in-situ armor remains known at that point, became every artist's favorite ankylosaurid model).
Anyway, Ankylosaurus armor is sometimes compared to Euoplocephalus, but isn't all that similar; in particular, the animal had some very large scutes. 
Saichania chulsanensis Maryanska, 1977 ?mid Campanian (LK) of Mongolia This ankylosaurine had unusual crescent-shaped armor plates around the neck, and armor on the belly region, a rare find.  Its arms were very short and massive, leading to a very low-slung animal.
Tarchia gigantea Maryanska, 1977 (originally Dyoplosaurus giganteus Maleev, 1956) early Maastrichtian (LK) of Mongolia Tarchia is the largest known Mongolian ankylosaurine, at over eight meters in length.  It had a large head, relatively tall for an ankylosaurid.  The type exhibits partially-healed skull injuries, both internal and external, suggestive of a tyrannosaurid attack.  It may have been a close relative of Saichania.  Remains from several individuals are known.
Talarurus plicatospineus Maleev, 1952 (including Syrmosaurus disparoserratus Maleev, 1952 [Maleevus Tumanova, 1987] and ?Amtosaurus magnus (N.D.) Kurzanov and Tumanova, 1978) ?Santonian (LK) of Mongolia Talarurus was an ankylosaurine with some similarities to Euoplocephalus, but with a weakly developed tail club.  Remains from at least five individuals are known, not including the partial skulls that contemporaneous Maleevus and Amtosaurus are based on, here considered conspecific with T. plicatospineus (although some researchers have in the past considered Amtosaurus to have been a hadrosaurid, or even too indeterminate for assignment beyond Ornithischia incertae sedis).  It has been suggested that it lived like a dinosaurian hippo.
Euoplocephalus:
Lambe, 1910		 E. tutus (Lambe, 1902 [originally Stereocephalus]) late middle Campanian-early Maastrichtian (LK) of Alberta and Montana The best-known ankylosaurine, Euoplocephalus is known from more than forty specimens, plus bits and pieces.  It is smaller than Tarchia and Ankylosaurus.  Remains named Dyoplosaurus may indicate a separate species, as shown by the variable tail clubs: some individuals have rounded clubs, while other seem to have points on theirs.  Traditionally, the synonym Scolosaurus (based on the excellent specimen in the British Museum of Natural History that preserves much of the dorsal armor in place, but unfortunately lacks the skull) was depicted with two rows of large dorsal spines, reaching a size maximum over the hips, and two large spikes on the tail club, while Dyoplosaurus was depicted with two rows of more subdued dorsal spines and no club spikes. 
Euoplocephalus was the first ankylosaurian known to have armored eyelids, although others are now known to have had them, too (Pawpawsaurus).  
Although cerapods are best known for complex jaw action, Euoplocephalus seems to have come up with its own method of chewing.
?E. acutosquameus (Parks, 1924 [originally Dyoplosaurus])
Pinacosaurus: Gilmore, 1933 P. grangeri (type) Gilmore, 1933 late Campanian (LK) of Mongolia and China Pinacosaurus is one of the best-known ankylosaurians, with over fifteen specimens referred to it, and is also one of the few ankylosaurians for which juvenile remains are known.  In one case, several juveniles were found huddled together, and had apparently died in a sandstorm.  Juvenile ankylosaurian skulls are particularly useful because it's not easy to tell where the major bones are underneath all the armor in adults, and patterns of bone location are useful in determining relationships.
P. mephistocephalus Godefroit, Pereda-Suberbiola, Li, and Dong, 1999 late Campanian (LK) of China The new second species is based on a subadult skeleton and skull with distinctively demonic horns (prompting the species name).

 

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