Ankylosauridae

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Ankylosaurids
Temporal range: Early Cretaceous - Late Cretaceous, 122–66 Ma
Euoplocephalus-tutus-1.jpg
Mounted skeleton of Euoplocephalus tutus, Senckenberg Museum
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Clade: Eurypoda
Suborder: Ankylosauria
Family: Ankylosauridae
Brown, 1908
Type species
Ankylosaurus magniventris
Brown, 1908
Subfamilies

Ankylosaurinae Brown, 1908

Synonyms

Syrmosauridae Maleev, 1952

An ankylosaurid is a member of the armored dinosaur family Ankylosauridae that appeared 122 million years ago (along with another family of ankylosaurs, the Nodosauridae) and became extinct 66 million years ago during the Cretaceous–Paleogene 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.

Features[edit]

Dyoplosaurus tail reconstruction, showing terms used for parts of ankylosaurid tails

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. Among all the ornithischians, the endocranial anatomy of ankylosaurs is the most poorly known.[1]

Armor[edit]

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.

Tail[edit]

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 bony tail clubs.

Relationships[edit]

Diagram showing ankylosaurid skull anatomy

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.[2]

Ankylosauria and Stegosauria are now grouped together within the clade Thyreophora. This group first appeared in the Sinemurian age, and survived for 135 million years, until disappearing in the Maastrichtian. They were widespread and inhabited a broad range of environments.[3][4] As more complete specimens and new genera have been discovered, theories about ankylosaurian interrelatedness have become more complex, and hypotheses have often changed between studies. In addition to Ankylosauridae, Ankylosauria has been divided into the families Nodosauridae, and sometimes Polacanthidae (these families lacked tail clubs).[5] Ankylosaurus is considered part of the subfamily Ankylosaurinae (members of which are called ankylosaurines) within Ankylosauridae.[5] Ankylosaurus appears to be most closely related to Anodontosaurus and Euoplocephalus.[6] The following cladogram is based on a 2015 phylogenetic analysis of the Ankylosaurinae conducted by Arbour and Currie:[7]

Vertebra
Cervical vertebra from the neck of AMNH 5895
Ankylosaurinae

Crichtonpelta




Tsagantegia



Zhejiangosaurus



Pinacosaurus





Saichania




Tarchia



Zaraapelta




Ankylosaurini

Dyoplosaurus





Talarurus



Nodocephalosaurus






Ankylosaurus



Anodontosaurus




Euoplocephalus




Scolosaurus



Ziapelta









Since Ankylosaurus and other Late Cretaceous North American ankylosaurids grouped with Asian genera (in a tribe the authors named Ankylosaurini), Arbour and Currie suggested that earlier North American ankylosaurids had gone extinct by the late Albian or Cenomanian ages of the Middle Cretaceous. Ankylosaurids thereafter recolonised North America from Asia during the Campanian or Turonian ages of the Late Cretaceous, and diversified there again, leading to genera such as Ankylosaurus, Anodontosaurus, and Euoplocephalus. This explains a 30 million year gap in the fossil record of North American ankylosaurids between these ages.[7]

Timeline of discoveries[edit]

21st century in paleontology 20th century in paleontology 19th century in paleontology 2090s in paleontology 2080s in paleontology 2070s in paleontology 2060s in paleontology 2050s in paleontology 2040s in paleontology 2030s in paleontology 2020s in paleontology 2010s in paleontology 2000s in paleontology 1990s in paleontology 1980s in paleontology 1970s in paleontology 1960s in paleontology 1950s in paleontology 1940s in paleontology 1930s in paleontology 1920s in paleontology 1910s in paleontology 1900s in paleontology 1890s in paleontology 1880s in paleontology 1870s in paleontology 1860s in paleontology 1850s in paleontology 1840s in paleontology 1830s in paleontology 1820s in paleontology Zhongyuansaurus Tsagantegia Tianzhenosaurus Tarchia Talarurus Shanxia Scolosaurus Saichania Pinacosaurus Oohkotokia Nodocephalosaurus Minotaurasaurus Euoplocephalus Dyoplosaurus Crichtonsaurus Anodontosaurus Ankylosaurus Ahshislepelta Shamosaurus Minmi Liaoningosaurus Gobisaurus Cedarpelta Aletopelta 21st century in paleontology 20th century in paleontology 19th century in paleontology 2090s in paleontology 2080s in paleontology 2070s in paleontology 2060s in paleontology 2050s in paleontology 2040s in paleontology 2030s in paleontology 2020s in paleontology 2010s in paleontology 2000s in paleontology 1990s in paleontology 1980s in paleontology 1970s in paleontology 1960s in paleontology 1950s in paleontology 1940s in paleontology 1930s in paleontology 1920s in paleontology 1910s in paleontology 1900s in paleontology 1890s in paleontology 1880s in paleontology 1870s in paleontology 1860s in paleontology 1850s in paleontology 1840s in paleontology 1830s in paleontology 1820s in paleontology

Timeline of genera[edit]

Cretaceous Jurassic Late Cretaceous Early Cretaceous Late Jurassic Middle Jurassic Early Jurassic Ankylosaurus Tarchia Saichania Anodontosaurus Oohkotokia Shanxia Tienzhenosaurus Aletopelta Ahshislepelta Nodocephalosaurus Euoplocephalus Dyoplosaurus Scolosaurus Pinacosaurus Minotaurasaurus Gobisaurus Tsagantegia Talarurus Crichtonsaurus Zhongyuansaurus Cedarpelta Shamosaurus Minmi Liaoningosaurus Cretaceous Jurassic Late Cretaceous Early Cretaceous Late Jurassic Middle Jurassic Early Jurassic

See also[edit]

References[edit]

  1. ^ Coombs W. (1978). "An endocranial cast of Euoplocephalus (Reptilia, Ornithischia)". Palaeontographia, Abteilung A 161: 176–82.
  2. ^ Hayashi, S., Carpenter, K., Scheyer, T.M., Watabe, M. and Suzuki. D. (2010). "Function and evolution of ankylosaur dermal armor." Acta Palaeontologica Polonica, 55(2): 213-228. doi:10.4202/app.2009.0103
  3. ^ Cite error: The named reference carpenter2004 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Coombs1978 was invoked but never defined (see the help page).
  5. ^ a b Thompson, R. S.; Parish, J. C.; Maidment, S. C. R.; Barrett, P. M. (2012). "Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)". Journal of Systematic Palaeontology 10 (2): 301. doi:10.1080/14772019.2011.569091.  edit
  6. ^ Arbour, V.M.; Currie, P.J.; Badamgarav, D. (2014). "The ankylosaurid dinosaurs of the Upper Cretaceous Baruungoyot and Nemegt formations of Mongolia". Zoological Journal of the Linnean Society 172: 631–652. doi:10.1111/zoj.12185. 
  7. ^ Cite error: The named reference systematics_ankylosaurid was invoked but never defined (see the help page).
  • Dinosaurs and other Prehistoric Creatures, edited by Ingrid Cranfield (2000), Salamander books, pg. 250-257.
  • Carpenter K (2001). "Phylogenetic analysis of the Ankylosauria". In Carpenter, Kenneth(ed). The Armored Dinosaurs. Indiana University Press. pp. 455–484. ISBN 0-253-33964-2. 
  • Kirkland, J. I. (1996). Biogeography of western North America's mid-Cretaceous faunas - losing European ties and the first great Asian-North American interchange. J. Vert. Paleontol. 16 (Suppl. to 3): 45A

External links[edit]