{{italictitle}}
{{italictitle}}{{Taxobox
| name =
Ankylosaurus
| fossil_range =
Late CretaceousThe Late Cretaceous is the youngest of two epochs in which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
| image = Ankylosaurus skull AMNH.jpg
| image_width = 250px
| image_caption = An
Ankylosaurus skull, profile view. This specimen is from the Edmonton Formation of Alberta.
| regnum =
AnimalAnimals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...
ia
| phylum =
ChordataChordates are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail...
| classis =
SauropsidaReptiles, or members of the class Reptilia, are air-breathing, generally "cold-blooded" amniotes that generally have skin covered in scales or scutes. They are tetrapods and lay amniote eggs, whose embryos are surrounded by the amnion membrane...
| superordo =
Dinosaur{{Otheruses}}{{pp-semi-protected|small=yes}}{{Otheruses}}{{pp-semi-protected|small=yes}}{{Taxobox|name = Dinosaurs|fossil_range = {{Fossil range|230|65|earliest=230|latest=0|PS=
Descendant taxon Aves survives to present.}}|image = field_dinos_2.jpg...
ia
| ordo = †
OrnithischiaOrnithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
| subordo = †
ThyreophoraThe Thyreophora were a subgroup of the ornithischian dinosaurs...
| infraordo = †
AnkylosauriaAnkylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are first known to have appeared in the early Jurassic Period of...
| familia = †
AnkylosauridaeAn ankylosaurid is a member of the Ankylosauridae family of armored dinosaurs that evolved 125 million years ago and became extinct 65 million years ago during the Cretaceous-Tertiary extinction event...
| genus =
†In biology and ecology, extinction is the end of an organism or group of taxa. The moment of extinction is generally considered to be the death of the last individual of that species...
Ankylosaurus
| genus_authority =
BrownBarnum Brown , born in Carbondale, Kansas, and named after the circus showman P.T. Barnum, was perhaps the most famous fossil hunter of the early twentieth century....
, 1908
|subdivision_ranks=
SpeciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
|subdivision=
- †A. magniventris Brown, 1908 (type
In taxonomy, a type species is a technical phrase, involved in the application of formal names...
)
}}
Ankylosaurus ({{pron-en|ˌæŋkɨlɵˈsɔrəs}}, which means 'fused lizard') is a
genusIn biology, a genus is a taxonomic unit used in the classification of living and fossil organisms. The term comes from Latin genus "descent, family, type, gender" , cognate with – genos, "race, stock, kin" ..In addition, genus is a taxonomic rank in the hierarchy In biology, a genus (plural:...
of ankylosaurid
dinosaur{{Otheruses}}{{pp-semi-protected|small=yes}}{{Otheruses}}{{pp-semi-protected|small=yes}}{{Taxobox|name = Dinosaurs|fossil_range = {{Fossil range|230|65|earliest=230|latest=0|PS=
Descendant taxon Aves survives to present.}}|image = field_dinos_2.jpg...
, containing one
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
,
A. magniventris.
FossilFossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous rock formations and sedimentary layers is known as the fossil record...
s of
Ankylosaurus are found in
geologic formationA formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
s dating to the very end of the
CretaceousThe Cretaceous , Latin language for "chalky", usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period of the...
Period in western
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
.
Although a complete skeleton has not been discovered and several other dinosaurs are represented by more extensive fossil material,
Ankylosaurus is often considered the
archetypalAn archetype is an original model of a person, ideal example, or a prototype after which others are copied, patterned, or emulated; a symbol universally recognized by all...
armoredArmour in animals is external or superficial protection against attack by predators, formed as part of the body , usually through the hardening of body tissues, outgrowths or secretions. It has therefore mostly developed in 'prey' species...
dinosaur. Other ankylosaurids shared its well-known features, like the heavily-armored body and massive bony tail club, but
Ankylosaurus was the largest member of its family.
Paleobiology
In comparison with modern land animals the adult
Ankylosaurus was very large. Some scientists have estimated a length of 9 meters (30 ft). Another reconstruction suggests a significantly smaller size, at 6.25 m (20.5 ft) long, up to 1.5 m (5 ft) wide and about 1.7 m (5.5 ft) high at the hip.
Ankylosaurus may have weighed over {{convert|6000|kg|lb}}. The body shape was low-slung and quite wide.
Ankylosaurus was
quadrupedQuadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
al, with the hind limbs longer than the forelimbs. Although its feet are still unknown to science, comparisons with other ankylosaurids suggest
Ankylosaurus probably had five toes on each foot. The
skullThe skull is a bony structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury....
was low and triangular in shape, wider than it was long. The largest known skull measures 64.5 centimeters (25 in) long and 74.5 cm (29 in) wide. Like other ankylosaurs,
Ankylosaurus was
herbivorousA herbivore is an animal that is adapted to eat plants and not meat.Herbivory is a form of predation in which an organism consumes principally autotrophs such as plants, algae and photosynthesizing bacteria....
, with small, leaf-shaped teeth suitable for cropping vegetation. These teeth were smaller, relative to the body size, than in any other ankylosaurid species.
Ankylosaurus did not share the grinding tooth batteries of the contemporaneous ceratopsid and
hadrosauridHadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...
dinosaurs, indicating that very little chewing occurred. Bones in the skull and other parts of the body were fused to increase their strength.
Armor
The most obvious feature of
Ankylosaurus is its armor, consisting of massive knobs and plates of bone, known as osteoderms or scutes, embedded in the skin. Osteoderms are also found in the skin of
crocodileA crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e...
s,
armadilloArmadillos are small placental mammals, known for having a leathery armor shell. The Dasypodidae are the only surviving family in the order Cingulata, part of the superorder Xenarthra along with the anteaters and sloths...
s and some
lizardLizards are a very large and widespread group of squamate reptiles, with nearly 5,000 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s. The bone was probably overlain by a tough, horny layer of
keratinKeratins are a family of fibrous structural proteins; tough and insoluble, they form the hard but un-mineralized structures found in reptiles, birds, amphibians, and mammals...
. These osteoderms ranged greatly in size, from wide, flat plates to small, round nodules. The plates were aligned in regular horizontal rows down the animal's neck, back, and hips, with the many smaller nodules protecting the areas between the large plates. Smaller plates may have been arranged on the limbs and tail. Compared to the slightly more ancient ankylosaurid
EuoplocephalusEuoplocephalus meaning 'well-armored head' was one of the largest genera of ankylosaurian dinosaurs, at about the size of a small elephant...
, the plates of
Ankylosaurus were smooth in texture, without the high keels found on the armor of the contemporaneous nodosaurid
EdmontoniaEdmontonia was an armoured dinosaur, a part of the nodosaur family from the Late Cretaceous Period. It is named after the Edmonton Formation , the unit of rock it was found in.-Description:...
. A row of flat, triangular spikes may have protruded laterally along each side of the tail. Tough, rounded scales protected the top of the skull, while four large
pyramidA pyramid is a building where the outer surfaces are triangular and converge at a point. The base of a pyramid can be trilateral, quadrilateral, or any polygon shape, meaning that a pyramid has at least four faces...
al horns projected outwards from its rear corners.
Tail club
The famous tail club of
Ankylosaurus was also composed of several large osteoderms, which were fused to the last few tail
vertebraA vertebra is an individual bone in the flexible column that defines vertebrate animals, e.g. humans. The vertebral column encases and protects the spinal cord, which runs from the base of the cranium down the dorsal side of the animal until reaching the pelvis. From there, vertebra continue into...
e. It was heavy and supported by the last seven tail vertebrae, which interlocked to form a stiff rod at the base of the club. Thick
tendonA tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fascia as they are all made of collagen except that ligaments join one bone to another bone, and fascia connect muscles to other...
s have been preserved, which attached to these vertebrae. These tendons were partially ossified (or bony) and were not very elastic, allowing great force to be transmitted to the end of the tail when it was swung. It seems to have been an active defensive weapon, capable of producing enough of a devastating impact to break the bones of an assailant. A 2009 study showed that large tail knobs could generate sufficient force to break bone during impacts, but average and small knobs could not, and that tail swinging behavior is feasible in ankylosaurids, but it remains unknown whether the tail was used for interspecific defense, intraspecific combat, or both. It has also been proposed that the tail club acted as a decoy for the head, although this idea is now largely discredited.
Environment
Ankylosaurus magniventris existed between 68 to 65.5 million years ago, in the final
MaastrichtianThe Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
stage of the
Late CretaceousThe Late Cretaceous is the youngest of two epochs in which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
Period, and was one of the dinosaurs to survive until the
Cretaceous-Tertiary extinction eventThe Cretaceous–Tertiary extinction event, which occurred approximately , was a large-scale mass extinction of animal and plant species in a geologically short period of time. Widely known as the K–T extinction event, it is associated with a geological signature known as the K–T boundary, usually a...
. The type specimen is from the
Hell Creek FormationThe Hell Creek Formation is an intensely-studied division of Upper Cretaceous to lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana....
of Montana, while other specimens have been found in the
Lance FormationThe Lance Formation is a division of Late Cretaceous rocks in the western United States. Named after Lance Creek, Wyoming, the microvertebrate fossils and dinosaurs represent important components of the latest Mesozoic vertebrate faunas...
of
WyomingWyoming is a state in the Western United States. The majority of the state is dominated by the mountain ranges and rangelands of the Rocky Mountain West, while the easternmost section of the state includes part of a high elevation prairie region known as the High Plains. While the tenth largest...
and the
Scollard FormationThe Scollard Formation is an Upper Cretaceous to lower Palaeocene rock formation found in south-central Alberta, Canada.-Stratigraphy:The Scollard outcrops extensively along the banks of the Red Deer River in the area of Trochu, where it is found just below prairie level...
in
AlbertaAlberta is one of Canada's prairie provinces. It became a province on September 1, 1905.Alberta is located in western Canada, bounded by the provinces of British Columbia to the west and Saskatchewan to the east, the Northwest Territories to the north, and the U.S. state of Montana to the south....
,
CanadaCanada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean...
, all of which date to the end of the Cretaceous.
The Lance, Hell Creek and Scollard Formations represent different sections of the western shore of the
shallow seaThe Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves during most of the mid and late Cretaceous Period.-Origin and geology:The Seaway was created as the...
that divided western and eastern North America during the Cretaceous. They represent a broad coastal plain, extending westward from the seaway to the newly formed
Rocky MountainsThe Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in Canada, to New Mexico, in the United States. The range's highest peak is Mount Elbert in Colorado at above sea level...
. These formations are composed largely of
sandstoneSandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any color, but the most common colors are tan, brown, yellow,...
and
mudstoneMudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
, which have been attributed to
floodplain||-||-||-||-||-||-||-||}A floodplain, or flood plain, is flat or nearly flat land adjacent to a stream or river that experiences occasional or periodic flooding...
environments. The Hell Creek is the best studied of these ancient environments. At the time, this region was subtropical, with a warm and humid climate. Many plant species were supported, primarily angiosperms, with less common conifers,
fernA fern is any one of a group of about 20,000 species of plants classified in the phylum or division Pteridophyta, also known as Filicophyta. The group is also referred to as Polypodiophyta, or Polypodiopsida when treated as a subdivision of tracheophyta...
s and
cycadCycads are a group of seed plants characterized by a large crown of compound leaves and a stout trunk. They are evergreen, gymnospermous, dioecious plants having large pinnately compound leaves...
s. An abundance of fossil leaves found at dozens of different sites indicates that the area was largely forested by small trees.
Fossils of
Ankylosaurus are considerably rare in these sediments, compared to
EdmontosaurusEdmontosaurus is a genus of crestless duck-billed dinosaur. The fossils of this animal have been found in rocks of western North America that date from the late Campanian stage to the end of the Maastrichtian stage of the Cretaceous Period, between 73 and 65.5 million years ago...
and the super-abundant
TriceratopsTriceratops is a genus of herbivorous ceratopsid dinosaur which lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65 million years ago in what is now North America. It was one of the last dinosaur genera to appear before the great Cretaceous–Tertiary...
, which make up most of the large herbivore fauna. Another ankylosaur,
Edmontonia, is also found in the same formations. However,
Ankylosaurus and
Edmontonia seem to have been separated both geographically and ecologically.
Ankylosaurus had a wide muzzle, perhaps used for non-selective
grazingGrazing generally describes a type of predation in which an herbivore feeds on plants , and also on other multicellular autotrophs...
and may have been limited to the upland regions, away from the coast, while
Edmontonia had a narrower muzzle, indicating a more selective diet, and seems to have lived at lower elevations, closer to the coast.
Classification
Ankylosaurus was named as the type genus of the family Ankylosauridae. Ankylosaurids are members of the larger taxon Ankylosauria, which also contains the nodosaurids. Ankylosaur phylogeny is a contentious topic, with several mutually exclusive analyses presented in recent years, so the exact position of
Ankylosaurus within Ankylosauridae is unknown.
Ankylosaurus and
Euoplocephalus are often thought to be sister taxa. However, other analyses have found these genera in different positions. Further discoveries or research may clarify the situation.
Discovery
Ankylosaurus was named by
AmericanThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
paleontologist
Barnum BrownBarnum Brown , born in Carbondale, Kansas, and named after the circus showman P.T. Barnum, was perhaps the most famous fossil hunter of the early twentieth century....
, in 1908. The generic name is derived from the
GreekAncient Greek is the historical stage in the development of the Greek language spanning across the Archaic , Classical , and Hellenistic periods of ancient Greece and the ancient world. It is predated in the 2nd millennium BC by Mycenaean Greek...
words
αγκυλος/
ankulos ('curved') and
σαυρος/
sauros ('lizard'). Brown intended this name in the same sense as the medical term
ankylosisAnkylosis, or Anchylosis is a stiffness of a joint, the result of injury or disease. The rigidity may be complete or partial and may be due to inflammation of the tendinous or muscular structures outside the joint or of the tissues of the joint itself...
, to refer to the stiffness produced by the fusion of many bones in the skull and body, so the name is often translated as 'stiffened lizard.' The
type speciesIn taxonomy, a type species is a technical phrase, involved in the application of formal names...
is
A. magniventris, from the
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. Through the Roman conquest, Latin spread throughout the Mediterranean and a large part of Europe...
magnus ('great') and
venter ('belly'), referring to the great width of the animal's body.
A team led by Brown discovered the type specimen of
A. magniventris (
AMNH 5895) in the Hell Creek Formation of Montana, in 1906. This consisted of the top of the skull, as well as vertebrae, ribs, part of the shoulder girdle and armor. Six years earlier, Brown found the skeleton of a large theropod dinosaur (
AMNH 5866) in the Lance Formation of Wyoming. This specimen was named
Dynamosaurus imperiosus in 1905 but is now thought to belong to
Tyrannosaurus rexTyrannosaurus was a genus of theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other tyrannosaurids...
. Associated with AMNH 5866 were more than 75 osteoderms of various sizes, which were attributed to
Dynamosaurus. However, these osteoderms are nearly identical in form to those of
A. magniventris and most probably belong to this species. In 1910, while on an expedition to Alberta, Barnum Brown recovered his third specimen of
A. magniventris (
AMNH 5214), from the Scollard Formation. AMNH 5214 includes a complete skull and the first known tail club, as well as ribs, limb bones and armor. All three of the above specimens are now housed at the
American Museum of Natural HistoryThe American Museum of Natural History , located on the Upper West Side, Manhattan, New York, USA, is one of the largest and most celebrated museums in the world...
in
New York CityNew York is the most populous city in the United States, and the center of the New York metropolitan area, which is among the most populous urban areas in the world. A leading global city, New York exerts a powerful influence over worldwide commerce, finance, culture, fashion and entertainment...
. The largest known skull of this animal (
NMC 8880) was collected in Alberta by Charles M. Sternberg, in 1947 and is now housed at the
Canadian Museum of NatureThe Canadian Museum of Nature is a natural history museum in Ottawa, Ontario, Canada. Its collections, which were started by the Geological Survey of Canada in 1856, include all aspects of the intersection of human society and nature, from gardening to gene-splicing...
. Many other isolated bones, armor plates and teeth have been found over the years.
In popular culture
Since its description in 1908,
Ankylosaurus has been publicized as the archetypal armored dinosaur, and due to its easily recognizable appearance and the intense public interest in dinosaurs,
Ankylosaurus has been a feature of worldwide
popular culturePopular culture is the totality of ideas, perspectives, attitudes, memes, images and other phenomena that are deemed preferred per an informal consensus within the mainstream of a given culture...
for many years. A life-sized reconstruction of
Ankylosaurus featured at the
1964 World's FairThe 1964/1965 New York World's Fair was the third major World's Fair to be held in New York City.-Overview:The site is Flushing Meadows Corona Park in the Borough of Queens and held both the 1964/1965 New York World’s Fair and the 1939/1940 New York World’s Fair...
in New York City greatly contributed to its popularity.
Ankylosaurus has also been featured on several
televisionTelevision is a widely used telecommunication medium for transmitting and receiving moving images, either monochromatic or color, usually accompanied by sound. "Television" may also refer specifically to a television set, television programming or television transmission...
documentaryDocumentary film is a broad category of visual expressions that is based on the attempt, in one fashion or another, to "document" reality. Although "documentary film" originally referred to movies shot on film stock, it has subsequently expanded to include video and digital productions that can...
miniseriesA miniseries , in a serial storytelling medium, is a production which tells a story in a pre-planned limited number of episodes. The exact number is open to interpretation; however, they are usually limited to fewer than a whole season. The term "miniseries" is generally a North American term...
, including
Walking with DinosaursWalking with Dinosaurs was a six-part documentary television mini-series that was produced by the BBC, narrated by Kenneth Branagh, and first aired in the UK in 1999. The series was subsequently aired in North America on the Discovery Channel in 2000, with Branagh's voice replaced with that of...
(1999) and
The Truth About Killer DinosaursThe Truth About Killer Dinosaurs is a two-part BBC documentary, presented by Bill Oddie, in which a group of scientists test out the strength of dinosaur weaponry using biomechanics. The first episode determines the winner of a battle between Tyrannosaurus and Triceratops, and second compares the...
(2005).
External links
{{portalpar|Dinosaurs}}