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Khalid Swift
Khalid Swift


Arbour looked at a number of early ankylosaurids including: Liaoningosaurus which lived 122 million years ago; Gobisaurus, which lived 90 million years ago; and Pinacosaurus, which lived 75 million years ago and is the earliest specimen with a complete tail club, to determine which of three possible evolutionary paths was most likely.


Abstract: Ankylosaurid ankylosaurs were quadrupedal, herbivorous dinosaurs with abundant dermal ossifications. They are best known for their distinctive tail club composed of stiff, interlocking vertebrae (the handle) and large, bulbous osteoderms (the knob), which may have been used as a weapon. However, tail clubs appear relatively late in the evolution of ankylosaurids, and seemed to have been present only in a derived clade of ankylosaurids during the last 20 million years of the Mesozoic Era. New evidence from mid Cretaceous fossils from China suggests that the evolution of the tail club occurred at least 40 million years earlier, and in a stepwise manner, with early ankylosaurids evolving handle-like vertebrae before the distal osteoderms enlarged and coossified to form a knob.

The osteoderms of all ankylosaurs (dinosaurs in Ankylosaurus' suborder, Ankylosauria) were composed of an thin outer cortical or compact bone and an thick inner cancellous bone (spongy, porous bone), according to an analysis Carpenter and his colleagues published in the journal Acta Palaeontologica Polonica in 2010. The osteoderms were probably covered with skin and keratin, the fibrous protein that makes up hair and nails in people.

Ankylosaurus moved on all four limbs, and its hind limbs were slightly longer than its forelimbs. Though there are insufficient foot fossils to establish whether Ankylosaurus had toes, it's believed the dinosaurs likely had five toes on each foot like other ankylosaurs.

Ankylosaurs had a complex nasal passage and a large cavity volume for the olfactory region of their skulls. The looping nasal cavity probably didn't improve smell much and instead was important for things like regulating temperature, according to a 2011 study in the Journal of Anatomy. However, ankylosaurs seemed to have had a large olfactory bulb (brain structure involved in the sense of smell), so the dinosaurs likely had a strong sense of smell to help seek out food and avoid predators, the study suggested.

Bony cranial ornamentation is developed by many groups of vertebrates, including ankylosaur dinosaurs. To date, the morphology and ontogenetic origin of ankylosaurian cranial ornamentation has primarily focused on a limited number of species from only one of the two major lineages, Ankylosauridae. For members of the sister group Nodosauridae, less is known. Here, we provide new details of the cranial anatomy of the nodosaurid Hungarosaurus from the Santonian of Europe. Based on a number of previously described and newly identified fragmentary skulls and skull elements, we recognize three different size classes of Hungarosaurus. We interpret these size classes as representing different stages of ontogeny. Cranial ornamentation is already well-developed in the earliest ontogenetic stage represented herein, suggesting that the presence of outgrowths may have played a role in intra- and interspecific recognition. We find no evidence that cranial ornamentation in Hungarosaurus involves the contribution of coossified osteoderms. Instead, available evidence indicates that cranial ornamentation forms as a result of the elaboration of individual elements. Although individual differences and sexual dimorphism cannot be excluded, the observed variation in Hungarosaurus cranial ornamentation appears to be associated with ontogeny.

The researchers report that the dinosaur met its fate in a body of water of some sort and was quickly covered in sediment, which acted as a very good preservation material. In addition to bones, the team was also able to make out the remains of soft tissue which, included spike sheaths and scales. The sediment also helped keep the specimen together in its original configuration, offering an unprecedented representation of how the creature looked while still alive. The team also notes that they are hoping that further study of the remains will help fill in gaps in the ankylosaurs record.

New research indicates that the tail clubs on huge armored dinosaurs known as ankylosaurs may have evolved to whack each other rather than deter hungry predators. This is a complete shift from what was previously believed.

She recommended further research, noting that if ankylosaurs were using them for intraspecific combat, one might expect to see injuries along adult flanks, as an ankylosaur tail can only swing so far.

A trove of uniquely preserved ankylosaur fossils was found, among other treasures, during a series of international expeditions in Uzbekistan two decades ago. Three fragments of ankylosaur braincases were the subject of the recent study.

Stegouros elengassen's unique tail structure consists of a flat surface with a series of sharp, pointed blades along each side, reminiscent of the macuahuitl, an Aztec war club. The tail, however, represents only the beginning of the ways it is different from other ankylosaurs.

The bones were placed under CT and micro-CT scans in order to get a clear look at what was going on inside and how the pieces of the tail fit together. Five large osteoderms (bony deposits which form scales and plates) are completely fused. Further, the tail is shorter than typical ankylosaurs by approximately 10 vertebrae, which probably allowed Stegouros to keep its tail from dragging and helped to wield it as a weapon.

Palaeontologist Dr. Jordan Mallon says the evidence points to a phenomenon called "bloat-and-float," whereby the bloating carcasses of ankylosaurs would end up in a river, flip belly-side up due to the weight of their heavy armour, and then float downstream. The remains would wash ashore, where decomposition and then fossilization would seal the dinosaur remains in their upside-down death pose.

"Textbooks have touted that ankylosaur fossils are usually found upside down, but no one has gone back and checked the records to make sure that's the case," explains Mallon. The observations date from the 1930s. Indeed, the fossils of two star ankylosaurs described in 2017, Borealopelta from Alberta and Zuul from Montana, were found upside down.

Mallon examined 32 ankylosaur fossils from Alberta (of which 26 were found belly up), photos of specimens, field notes, and other signs such as erosion of the exposed surface, sun bleaching, and the presence of lichens.

"One idea was that ankylosaurs were simply clumsy, tripping over themselves or rolling down hills and ending up dying that way," he says. But since ankylosaurs existed for about 100 million years, clumsy habits would not fit with their apparent evolutionary success.

Another theory was that ankylosaurs were prey for carnivores, such as hungry tyrannosaurids, which would flip the armoured dinosaurs onto their backs to get at the soft underbelly. "If this was true, we would expect to see signs of bite marks, especially on upside-down ones, but we saw marks on only one specimen," explains Mallon. "Since they were armoured, it makes sense that ankylosaurs were not regularly preyed upon, and the fossil evidence in museum collections supports this."

"We designed these models of ankylosaurs, both clubless and clubbed, and looked at their floating behavior," explains Mallon. The computer modelling showed that the animals would tend to flip upside down quite easily in water. Nodosaurids, which are ankylosaurs with no tail clubs, would flip most easily at the slightest tilt; the ankyosaurids (with clubbed tails), were more stable but could still be flipped.

The Ankylosaurus is the largest species of ankylosaurid dinosaur, which originated in North America during the Late Cretaceous period. The base genome of the Ankylosaurus bred by InGen for Jurassic World are a dull greyish-brown color.

Recognizable by the large club at the end of its tail, Ankylosaurus is usually seen as the archetypical ankylosaur, but it had plenty of features unique to itself: It was a massive animal, far larger than any nodosaurid and even the average ankylosaurid. Its armor, like that of other ankylosaurids, was plate-like and lightweight, rather than the spiky, heavyweight defenses nodosaurids displayed. Its massive tail club was similar to that of Euoplocephalus, yet with slightly different proportions.[7][6]

Ankylosaurus lived 68 to 66 million years ago, in the Hell Creek, a floodplain ecosystem with warm subtropical climate.[7] Other dinosaurs known from that time and place are the tyrannosaurid Tyrannosaurus, the ceratopsids Triceratops and Torosaurus, the pachycephalosaurids Pachycephalosaurus, Stygimoloch, and Dracorex, the hadrosaurid Edmontosaurus, and a fellow ankylosaur, the nodosaurid Denversaurus.[8] Those were among the last non-avian dinosaurs to have ever lived.

Ankylosaurus was a low browsing generalist herbivore, perhaps more likely to eat fruit than earlier ankylosaurids. Niche partitioning ensured it wouldn't have competition issues with other herbivores.[7]

Soto-Acuña, of the Universidad de Chile in Santiago, and his team identified the new species based on a nearly complete skeleton discovered in the dry Patagonian region of Chile. With its slender limbs and unusually short tail, S. elengassen already looked markedly different from other ankylosaurs in many ways. But its cranium pegged the creature as a type of early ankylosaur, the team found.

Pinacosaurus, a species of ankylosaur studied by researchers, didn't possess the classic syrinx like other animals to produce sound. However, its large and kinetic larynx served a key purpose - airway protection!

Oddly enough, the silhouette representing Ankylosaurus seen on the Jurassic World website and on the Holoscape isn't based on Ankylosaurus, but on a reconstruction of the basal ankylosaurian Kunbarrasaurus ieversi (formerly referred to the genus Minmi as Minmi sp.). 041b061a72

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