Everything about Ankylosaurus totally explained
Ankylosaurus (meaning '
rigid lizard') is a
genus of
ankylosaurid dinosaur, containing one
species,
A. magniventris.
Fossils of
Ankylosaurus are found in
geologic formations dating to the very end of the
Cretaceous Period in western
North America.
Although a complete skeleton hasn't been discovered and several other dinosaurs are represented by more extensive fossil material,
Ankylosaurus is often considered the
archetypal armored 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
A full-grown
Ankylosaurus was a very large animal, compared to the majority of modern land animals. 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. The body shape was low-slung and quite wide.
Ankylosaurus was
quadrupedal, 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
skull 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
herbivorous, with small, leaf-shaped teeth suitable for cropping vegetation.
Ankylosaurus didn't share the grinding tooth batteries of the contemporaneous
ceratopsid and
hadrosaurid 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, embedded in the skin. Osteoderms are also found in the skin of
crocodiles,
armadillos and some
lizards. The bone was probably overlain by a tough, horny layer of
keratin. 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
Euoplocephalus, the plates of
Ankylosaurus were smooth in texture, without the high keels found on the armor of the contemporaneous
nodosaurid Edmontonia. 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
pyramidal horns projected outwards from its rear corners.
Environment
Ankylosaurus magniventris existed between 68 to 65.5
million years ago, in the final
Maastrichtian stage of the
Late Cretaceous Period, and was one of the dinosaurs to survive until the
Cretaceous-Tertiary extinction event. The
type specimen is from the
Hell Creek Formation of Montana, while other specimens have been found in the
Lance Formation of
Wyoming and the
Scollard Formation in
Alberta,
Canada, 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 sea that divided western and eastern North America during the Cretaceous. They represent a broad coastal plain, extending eastward from the seaway to the newly formed
Rocky Mountains. These formations are composed largely of
sandstone and
mudstone, which have been attributed to
floodplain 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,
ferns and
cycads. 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
Edmontosaurus and the super-abundant
Triceratops, 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
grazing 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. 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. Further discoveries or research may clarify the situation.
Discovery
Ankylosaurus was named by
American paleontologist Barnum Brown, in 1908. The generic name is derived from the
Greek words
αγκυλος/
ankulos ('curved') and
σαυρος/
sauros ('lizard'). Brown intended this name in the same sense as the medical term
ankylosis, 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 species is
A. magniventris, from the
Latin 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 rex. 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 History in
New York City. 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 Nature. 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 culture for many years. A life-sized reconstruction of
Ankylosaurus featured at the
1964 World's Fair in New York City greatly contributed to its popularity.
Several
motion picture series have featured ankylosaurs.
Ankylosaurus has brief cameos in the
animated The Land Before Time series throughout the late 1980s and 1990s, though never a large part, and is one of several types of dinosaur shown grazing together in the 2001 film
Jurassic Park III and its
video games. HardRock from the animated television program
Extreme Dinosaurs (1998) is an
Ankylosaurus.
Ankylosaurus has also been featured on several
television documentary miniseries, including
Walking with Dinosaurs (1999) and
The Truth About Killer Dinosaurs (2005).
It has also been featured in computer games like
Zoo Tycoon, and
several Jurassic Park
games. While some of these games depict
Ankylosaurus as a difficult target, others present the genus as slow-moving, weak herbivores.
Further Information
Get more info on 'Ankylosaurus'.
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