Jump to content

Tyrannosaurus

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by 203.166.242.209 (talk) at 12:39, 20 August 2007. The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Tyrannosaurus
Temporal range: Late Cretaceous
Fossil skeleton at the
National Museum of Natural History, Washington, D.C.
Scientific classification
Kingdom:
Animalia

  • T. rex (type)
    Osborn, 1905

Tyrannosaurus (IPA pronunciation [tɪˌɹænəˈsɔɹəs] or [taɪ-], meaning 'tyrant lizard') is a genus of theropod dinosaur. The species Tyrannosaurus rex, commonly abbreviated to T. rex, is one of the dinosaurs most often featured in popular culture around the world. It hails from what is now western North America. Some scientists consider Tarbosaurus bataar from Asia to represent a second species of Tyrannosaurus, while others maintain Tarbosaurus as a separate genus. Other species have also been described, but these were either concluded to be synonymous with Tyrannosaurus rex or removed from the genus.[1]

Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small and they retained only two digits. Although other theropods rivaled or exceeded T. rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring up to approximately 13 metres (43 feet) in length and up to 6.8 metric tons (7.5 short tons) in weight.

Fossils of T. rex have been found in North American rock formations dating to the last three million years of the Cretaceous Period at the end of the Maastrichtian stage, approximately 68.5 to 65.5 million years ago; it was among the last dinosaurs to exist prior to the Cretaceous-Tertiary extinction event. More than 30 specimens of T. rex have been identified, some of which are nearly complete skeletons. Some researchers have discovered soft tissue as well. The abundance of fossil material has allowed significant research into many aspects of its biology, including life history and biomechanics. The feeding habits, physiology and potential speed of T. rex are a few of the topics which remain controversial.

Description

Tyrannosaurus rex was one of the largest land carnivores of all time, measuring 12 to 13 meters (40 to 43.3 feet) long, and 4.5-5 m (14-16.6 ft) tall, when fully-grown.[2] Mass estimates have varied widely over the years, from more than 7,200 kilograms (8 tons),[3] to less than 4,500 kg (5 tons),[4][5] with most modern estimates ranging between 5,400 and 6,800 kg (between 6 and 7.5 tons).[6][7][8][9]

Various specimens of Tyrannosaurus rex with a human for scale.

The largest known T. rex skulls measure up to 1.5 m (5 ft) in length. Compared to other theropods, the skull was heavily modified. The skull was extremely wide posteriorly, with a narrow snout, allowing some degree of binocular vision. Some of the bones, such as the nasals, were fused, preventing movement between them. Large fenestrae (openings) in the skull reduced weight and provided areas for muscle attachment. The bones themselves were massive, as were the serrated teeth which, rather than being bladelike, were oval in cross-section. Like other tyrannosaurids, T. rex displayed marked heterodonty, with the premaxillary teeth at the front of the upper jaw closely-packed and D-shaped in cross-section. Large bite marks found on bones of other dinosaurs indicate that these teeth could penetrate solid bone. T. rex had the greatest bite force of any dinosaur and one of the strongest bite forces of any animal. Worn or broken teeth are often found, but unlike those of mammals, tyrannosaurid teeth were continually replaced throughout the life of the animal.[2]

The neck of T. rex formed a natural S-shaped curve like that of other theropods, but was short and muscular to support the massive head. The two-fingered forelimbs were very small relative to the size of the body, but heavily built. In contrast, the hindlimbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso. To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow. This reduced the weight of the skeleton while maintaining much of the strength of the bones.[2]

Classification

File:T. rex head rhs.JPG
T. rex head reconstruction at the Oxford University Museum of Natural History.

Tyrannosaurus is the type genus of the superfamily Tyrannosauroidea, the family Tyrannosauridae, and the subfamily Tyrannosaurinae. Other members of the tyrannosaurine subfamily include the North American Daspletosaurus and the Asian Tarbosaurus,[10][11] both of which have occasionally been synonymized with Tyrannosaurus.[12] Tyrannosaurids were once commonly thought to be descendants of earlier large theropods such as megalosaurs and carnosaurs, although more recently they were reclassified with the generally smaller coelurosaurs.[13]

In 1955, Soviet paleontologist Evgeny Maleev named a new species, Tyrannosaurus bataar, from Mongolia.[14] By 1965, this species had been renamed Tarbosaurus bataar.[15] Despite the renaming, many phylogenetic analyses have found Tarbosaurus bataar to be the sister taxon of Tyrannosaurus rex,[11] and it has often been considered an Asian species of Tyrannosaurus.[13][16][17] A recent redescription of the skull of Tarbosaurus bataar has shown that it was much narrower than that of Tyrannosaurus rex and that during a bite, the distribution of stress in the skull would have been very different, closer to that of Alioramus, another Asian tyrannosaur.[18] A related cladistic analysis found that Alioramus, not Tyrannosaurus, was the sister taxon of Tarbosaurus, which, if true, would suggest that Tarbosaurus and Tyrannosaurus should remain separate.[10]

Other tyrannosaurid fossils found in the same formations as T. rex were originally classified as separate taxa, including Aublysodon and Albertosaurus megagracilis,[12] the latter being named Dinotyrannus megagracilis in 1995.[19] However, these fossils are now universally considered to belong to juvenile T. rex.[20] A small but nearly complete skull from Montana, 60 cm (2 ft) long, may be an exception. This skull was originally classified as a species of Gorgosaurus (G. lancensis) by Charles W. Gilmore in 1946,[21] but was later referred to a new genus, Nanotyrannus.[22] Opinions remain divided on the validity of N. lancensis. Many paleontologists consider the skull to belong to a juvenile T. rex.[23] There are minor differences between the two species, including the higher number of teeth in N. lancensis, which lead some scientists to recommend keeping the two genera separate until further research or discoveries clarify the situation.[11][24]

Manospondylus controversy

Skull of T. rex, type specimen at the Carnegie Museum of Natural History. This was heavily and inaccurately restored with plaster after Allosaurus, and has since been disassembled.

The first fossil specimen which can be attributed to Tyrannosaurus rex consists of two partial vertebrae (one of which has been lost) found by Edward Drinker Cope in 1892 and described as Manospondylus gigas. Osborn recognized the similarity between M. gigas and T. rex as early as 1917 but, due to the fragmentary nature of the Manospondylus vertebrae, he could not synonymize them conclusively.[25]

Controversy erupted in June 2000 after the Black Hills Institute located the type locality of M. gigas in South Dakota and unearthed more tyrannosaur bones there. These were judged to represent further remains of the same individual, and to be identical to those of T. rex. According to the rules of the International Code of Zoological Nomenclature (ICZN), the system that governs the scientific naming of animals, Manospondylus gigas should therefore have priority over Tyrannosaurus rex, because it was named first.[26] However, the Fourth Edition of the ICZN, which took effect on January 1 2000, states that "the prevailing usage must be maintained" when "the senior synonym or homonym has not been used as a valid name after 1899" and "the junior synonym or homonym has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years..."[27] Tyrannosaurus rex easily qualifies as the valid name under these conditions and would most likely be considered a nomen protectum ("protected name") under the ICZN if it was ever challenged, which it has not yet been. Manospondylus gigas would then be deemed a nomen oblitum ("forgotten name").[28]

Paleobiology

As with all dinosaurs known only from the fossil record, much of Tyrannosaurus biology, including behavior, coloration, ecology, and physiology, remains unknown. However, many new specimens have been discovered in the last twenty years, which has allowed some informed speculation on growth patterns, sexual dimorphism, biomechanics, and metabolism.

Life history

A graph showing the hypothesized growth curves (body mass versus age) of four tyrannosaurids. Tyrannosaurus rex is drawn in black. Based on Erickson et al. 2004.

The identification of several specimens as juvenile Tyrannosaurus rex has allowed scientists to document ontogenetic changes in the species, estimate the lifespan, and determine how quickly the animals would have grown. The smallest known individual (LACM 28471, the "Jordan theropod") is estimated to have weighed only 29.9 kg (66 lb), while the largest, such as FMNH PR2081 ("Sue") most likely weighed over 5400 kg (6 short tons). Histologic analysis of T. rex bones showed LACM 28471 had aged only 2 years when it died, while "Sue" was 28 years old, an age which may have been close to the maximum for the species.[9]

Histology has also allowed the age of other specimens to be determined. Growth curves can be developed when the ages of different specimens are plotted on a graph along with their mass. A T. rex growth curve is S-shaped, with juveniles remaining under 1800 kg (2 short tons) until approximately 14 years of age, when body size began to increase dramatically. During this rapid growth phase, a young T. rex would gain an average of 600 kg (1600 lb) a year for the next four years. At 18 years of age, the curve plateaus again, indicating that growth slowed dramatically. For example, only 600 kg (1,300 lb) separated the 28-year-old "Sue" from a 22-year-old Canadian specimen (RTMP 81.12.1).[9] Another recent histological study performed by different workers corroborates these results, finding that rapid growth began to slow at around 16 years of age.[29] This sudden change growth rate may indicate physical maturity, a hypothesis which is supported by the discovery of medullary tissue in the femur of a 16 to 20-year-old T. rex from Montana (MOR 1125, also known as "B-rex"). Medullary tissue is found only in female birds during ovulation, indicating that "B-rex" was of reproductive age.[30] Other tyrannosaurids exhibit extremely similar growth curves, although with lower growth rates corresponding to their lower adult sizes.[31]

Over half of the known T. rex specimens appear to have died within six years of reaching sexual maturity, a pattern which is also seen in other tyrannosaurs and in some large, long-lived birds and mammals today. These species are characterized by high infant mortality rates, followed by relatively low mortality among juveniles. Mortality increases again following sexual maturity, partly due to the stresses of reproduction. One study suggests that the rarity of juvenile T. rex fossils is due in part to low juvenile mortality rates; the animals were not dying in large numbers at these ages, and so were not often fossilized. However, this rarity may also be due to the incompleteness of the fossil record or to the bias of fossil collectors towards larger, more spectacular specimens.[31]

Sexual dimorphism

As the number of specimens increased, scientists began to analyze the variation between individuals and discovered what appeared to be two distinct body types, or morphs, similarly to some other theropod species. As one of these morphs was more solidly built, it was termed the 'robust' morph while the other was termed 'gracile.' Several morphological differences associated with the two morphs were used to analyze sexual dimorphism in Tyrannosaurus rex, with the 'robust' morph usually suggested to be female. For example, the pelvis of several 'robust' specimens seemed to be wider, perhaps to allow the passage of eggs.[32] It was also thought that the 'robust' morphology correlated with a reduced chevron on the first tail vertebra, also ostensibly to allow eggs to pass out of the reproductive tract, as had been erroneously reported for crocodiles.[33]

In recent years, evidence for sexual dimorphism has been weakened. A 2005 study reported that previous claims of sexual dimorphism in crocodile chevron anatomy were in error, casting doubt on the existence of similar dimorphism between T. rex genders.[34] A full-sized chevron was discovered on the first tail vertebra of "Sue," an extremely robust individual, indicating that this feature could not be used to differentiate the two morphs anyway. As T. rex specimens have been found from Saskatchewan to New Mexico, differences between individuals may be indicative of geographic variation rather than sexual dimorphism. The differences could also be age-related, with 'robust' individuals being older animals.[2]

Only a single T. rex specimen has been conclusively shown to belong to a specific gender. Examination of "B-rex" demonstrated the preservation of soft tissue within several bones. Some of this tissue has been identified as medullary tissue, a specialized tissue grown only in modern birds as a source of calcium for the production of eggshell during ovulation. As only female birds lay eggs, medullary tissue is only found naturally in females, although males are capable of producing it when injected with female reproductive hormones like estrogen. This strongly suggests that "B-rex" was female, and that she died during ovulation.[30] Recent research has shown that medullary tissue is never found in crocodiles, which are thought to be the closest living relatives of dinosaurs, aside from birds. The shared presence of medullary tissue in birds and theropod dinosaurs is further evidence of the close evolutionary relationship between the two.[35]

Posture

File:Tyrannosaurusrex01.gif
Outdated reconstruction (by Charles R. Knight), showing 'tripod' pose.
Replica at Senckenberg Museum, showing modern view of posture.

Like many bipedal dinosaurs, Tyrannosaurus rex was historically depicted as a 'living tripod', with the body at 45 degrees or less from the vertical and the tail dragging along the ground, similar to a kangaroo. This concept dates from Joseph Leidy's 1865 reconstruction of Hadrosaurus, the first to depict a dinosaur in a bipedal posture.[36] Henry Fairfield Osborn, former president of the American Museum of Natural History (AMNH) in New York City, who believed the creature stood upright, further reinforced the notion after unveiling the first complete T. rex skeleton in 1915. It stood in this upright pose for nearly a century, until it was dismantled in 1992.[37] By 1970, scientists realized this pose was incorrect and could not have been maintained by a living animal, as it would have resulted in the dislocation or weakening of several joints, including the hips and the articulation between the head and the spinal column.[38] Despite its inaccuracies, the AMNH mount inspired similar depictions in many films and paintings (such as Rudolph Zallinger's famous mural The Age Of Reptiles in Yale University's Peabody Museum of Natural History) until the 1990s, when films such as Jurassic Park introduced a more accurate posture to the general public. Modern representations in museums, art, and film show T. rex with its body approximately parallel to the ground and tail extended behind the body to balance the head.[12]

Arms

Closeup of forelimb; specimen at National Museum of Natural History, Washington, DC.

When Tyrannosaurus rex was first discovered, the humerus was the only element of the forelimb known.[39] For the initial mounted skeleton as seen by the public in 1915, Osborn substituted longer, three-fingered forelimbs like those of Allosaurus.[25] However, a year earlier, Lawrence Lambe described the short, two-fingered forelimbs of the closely-related Gorgosaurus.[40] This strongly suggested that T. rex had similar forelimbs, but this hypothesis was not confirmed until the first complete T. rex forelimbs were identified in 1989, belonging to MOR 555 (the "Wankel rex").[41] The remains of "Sue" also include complete forelimbs.[2] T. rex 'arms' are very small relative to overall body size, measuring only 1 m (3 ft 3 in) long. However, they are not vestigial but instead show large areas for muscle attachment, indicating considerable strength. This was recognized as early as 1906 by Osborn, who speculated that the forelimbs may have been used to grasp a mate during copulation.[42] It has also been suggested that the forelimbs were used to assist the animal in rising from a prone position.[38] Another possibility is that the forelimbs held struggling prey while it was dispatched by the tyrannosaur's enormous jaws. This hypothesis may be supported by biomechanical analysis. T. rex forelimb bones exhibit extremely thick cortical bone, indicating that they were developed to withstand heavy loads. The biceps brachii muscle of a full-grown Tyrannosaurus rex was capable of lifting 199 kg (438 lb) by itself; this number would only increase with other muscles (like the brachialis) acting in concert with the biceps. A T. rex forearm also had a reduced range of motion, with the shoulder and elbow joints allowing only 40 and 45 degrees of motion, respectively. In contrast, the same two joints in Deinonychus allow up to 88 and 130 degrees of motion, respectively, while a human arm can rotate 360 degrees at the shoulder and move through 165 degrees at the elbow. The heavy build of the arm bones, extreme strength of the muscles, and limited range of motion may indicate a system designed to hold fast despite the stresses of a struggling prey animal.[43]

Soft tissue

In the March 2005 issue of Science, Mary Higby Schweitzer of North Carolina State University and colleagues announced the recovery of soft tissue from the marrow cavity of a fossilized leg bone, from a 68 million-year-old Tyrannosaurus. The bone had been intentionally, though reluctantly, broken for shipping and then not preserved in the normal manner, specifically because Schweitzer was hoping to test it for soft tissue. Designated as the Museum of the Rockies specimen 1125, or MOR 1125, the dinosaur was previously excavated from the Hell Creek Formation. Flexible, bifurcating blood vessels and fibrous but elastic bone matrix tissue were recognized. In addition, microstructures resembling blood cells were found inside the matrix and vessels. The structures bear resemblance to ostrich blood cells and vessels. Whether an unknown process, distinct from normal fossilization, preserved the material, or the material is original, the researchers do not know, and they are careful not to make any claims about preservation.[44] If it is found to be original material, any surviving proteins may be used as a means of indirectly guessing some of the DNA content of the dinosaurs involved, because each protein is typically created by a specific gene. The absence of previous finds may merely be the result of people assuming preserved tissue was impossible, therefore simply not looking. Since the first, two more tyrannosaurs and a hadrosaur have also been found to have such tissue-like structures.[45] Research on some of the tissues involved have suggested that birds are closer relatives to tyrannosaurs than other modern animals.[46]

In subsequent studies reported in the journal Science in April 2007, Asara and colleagues concluded that seven traces of collagen proteins detected in purified T. rex bone most closely match those reported in chickens, followed by frogs and newts. The discovery of proteins from a creature tens of millions of years old, along with similar traces the team found in a mastodon bone at least 160,000 years old, upends the conventional view of fossils and may shift paleontologists' focus from bone hunting to biochemistry. Until these finds, most scientists presumed that fossilization replaced all living tissue with inert minerals. Paleontologist Hans Larsson of McGill University in Montreal, who was not part of the studies, called the finds "a milestone, and suggested that dinosaurs could "enter the field of molecular biology and really slingshot paleontology into the modern world."[47]

Skin

Main article: Feathered dinosaurs
A baby T. Rex, covered with down.

In 2004, the scientific journal Nature published a report describing an early tyrannosauroid, Dilong paradoxus, from the famous Yixian Formation of China. As with many other theropods discovered in the Yixian, the fossil skeleton was preserved with a coat of filamentous structures which are commonly recognized as the precursors of feathers. It has also been proposed that Tyrannosaurus and other closely-related tyrannosaurids had such protofeathers. However, rare skin impressions from adult tyrannosaurids in Canada and Mongolia show pebbly scales typical of other dinosaurs. While it is possible that protofeathers existed on parts of the body which have not been preserved, a lack of insulatory body covering is consistent with modern multi-ton mammals such as elephants, hippopotamus, and most species of rhinoceros. As an object increases in size, its ability to retain heat increases due to its decreasing surface area-to-volume ratio. Therefore, as large animals evolve in or disperse into warm climates, a coat of fur or feathers loses its selective advantage for thermal insulation and can instead become a disadvantage, as the insulation traps excess heat inside the body, possibly overheating the animal. Protofeathers may also have been secondarily lost during the evolution of large tyrannosaurids like Tyrannosaurus, especially in warm Cretaceous climates.[48]

Thermoregulation

Main article: Physiology of dinosaurs

Tyrannosaurus, like most dinosaurs, was long thought to have an ectothermic ("cold-blooded") reptilian metabolism. The idea of dinosaur ectothermy was challenged by scientists like Robert Bakker and John Ostrom in the early years of the "Dinosaur Renaissance", beginning in the late 1960s.[49][50] Tyrannosaurus rex itself was claimed to have been endothermic ("warm-blooded"), implying a very active lifestyle.[5] Since then, several paleontologists have sought to determine the ability of Tyrannosaurus to regulate its body temperature. Histological evidence of high growth rates in young T. rex, comparable to those of mammals and birds, may support the hypothesis of a high metabolism. Growth curves indicate that, as in mammals and birds, T. rex growth was limited mostly to immature animals, rather than the indeterminate growth seen in most other vertebrates.[29]

Oxygen isotope ratios in fossilized bone are sometimes used to determine the temperature at which the bone was deposited, as the ratio between certain isotopes correlates with temperature. In one specimen, the isotope ratios in bones from different parts of the body indicated a temperature difference of no more than 4 to 5°C (7 to 9°F) between the vertebrae of the torso and the tibia of the lower leg. This small temperature range between the body core and the extremities was claimed by paleontologist Reese Barrick and geochemist William Showers to indicate that T. rex maintained a constant internal body temperature (homeothermy) and that it enjoyed a metabolism somewhere between ectothermic reptiles and endothermic mammals.[51] Other scientists have pointed out that the ratio of oxygen isotopes in the fossils today does not necessarily represent the same ratio in the distant past, and may have been altered during or after fossilization (diagenesis).[52] Barrick and Showers have defended their conclusions in subsequent papers, finding similar results in another theropod dinosaur from a different continent and tens of millions of years earlier in time (Giganotosaurus).[53] Ornithischian dinosaurs also showed evidence of homeothermy, while varanid lizards from the same formation did not.[54] Even if Tyrannosaurus rex does exhibit evidence of homothermy, it does not necessarily mean that it was endothermic. Such thermoregulation may also be explained by gigantothermy, as in some living sea turtles.[55][56]

Feeding strategies

Tyrannosaurus rex skull and upper vertebral column, Palais de la Découverte, Paris.

Most debate about Tyrannosaurus centers on its feeding patterns and locomotion. One paleontologist, noted hadrosaur expert Jack Horner, claims that Tyrannosaurus was exclusively a scavenger and did not engage in active hunting at all.[41] Horner has only presented this in an official scientific context once, while mainly discussing it in his books and in the media. His hypothesis is based on the following: Tyrannosaurs have large olfactory bulbs and olfactory nerves (relative to their brain size). These suggest a highly developed sense of smell, allegedly used to sniff out carcasses over great distances. Tyrannosaur teeth could crush bone, a skill perhaps used to extract as much food (bone marrow) as possible from carcass remnants, usually the least nutritious parts. Since at least some of Tyrannosaurus's prey could move quickly, evidence that it walked instead of ran could indicate that it was a scavenger.[57][58]

Most scientists who have published on the subject since insist that Tyrannosaurus was both a predator and a scavenger, taking whatever meat it could acquire depending on the opportunity that was presented.[59] Modern carnivores such as lions and hyenas will often scavenge what other predators have killed, suggesting that tyrannosaurs may also have done so.[60]

Some other evidence exists that suggests hunting behavior in Tyrannosaurus. The ocular cavities of tyrannosaurs are positioned so that the eyes would point forward, giving the dinosaur binocular vision.[61] A scavenger might not need the advanced depth perception that stereoscopic vision affords; in modern animals, binocular vision is found primarily in predators.

File:T. rex right hind foot (med).JPG
T. rex right hind foot (medial view) Oxford University Museum of Natural History.

When examining Sue, paleontologist Pete Larson found a broken and healed fibula and tail vertebrae, scarred facial bones and a tooth from another Tyrannosaurus embedded in a neck vertebra. If correct, it might be strong evidence for aggressive behavior between tyrannosaurs but whether it would be competition for food and mates or active cannibalism is unclear.[62] However, further recent investigation of these purported wounds has shown that most are infections rather than injuries (or simply damage to the fossil after death) and the few injuries are too general to be indicative of intraspecific conflict.[63] In the Sue excavation site, an Edmontosaurus annectens skeleton was also found with healed tyrannosaur-inflicted scars on its tail. The fact that the scars seem to have healed suggests active predation instead of scavenging a previous kill.[64][65] Another piece of evidence is a Triceratops found with bite marks on its ilium. Again, these were inflicted by a tyrannosaur and they too appear healed.[66]

There have been conflicting studies regarding the extent to which Tyrannosaurus could run and exactly how fast it might have been; speculation has suggested speeds up to 70 km/h (45 mph) or even more. However, according to James Farlow, a palaeontologist at Indiana-Purdue University in Fort Wayne, Indiana, "If T. rex had been moving fast and tripped, it would have died."[67] If it tripped and fell while running, a tumbling tyrannosaur's torso would have slammed into the ground at a deceleration of 6 g (six times the acceleration due to gravity, or about 60 m/s²).[6] (See also Locomotion, below.)

Some argue that if Tyrannosaurus were a scavenger, another dinosaur had to be the top predator in the Amerasian Upper Cretaceous. Top prey were the larger marginocephalians and ornithopods. The other tyrannosaurids share so many characteristics that only small dromaeosaurs remain as feasible top predators. In this light, scavenger hypothesis adherents have suggested that the size and power of tyrannosaurs allowed them to steal kills from smaller predators.[58]

T. rex right hind foot (lateral) Oxford University Museum of Natural History.

Locomotion

Scientists who think that Tyrannosaurus was able to run slowly point out that hollow bones and other features that would have lightened its body may have kept adult weight to a mere 5 tons or so, or that other animals like ostriches and horses with long, flexible legs are able to achieve high speeds through slower but longer strides. Additionally, some have argued that Tyrannosaurus had relatively larger leg muscles than any animal alive today, which could have enabled fast running (40–70 km/h or 25–45 mph).[68]

Some old studies of leg anatomy and living animals suggested that Tyrannosaurus could not run at all and merely walked. The ratio of femur (thigh bone) to tibia (shank bone) length (greater than 1, as in most large theropods) could indicate that Tyrannosaurus was a specialized walker, like a modern elephant. In addition, it had tiny 'arms' that could not have stopped the dinosaur's fall, had it stumbled while running; standard estimates of Tyrannosaurus weight at 6 to 8 tons would produce a lethal impact force, should it have fallen.[69] It should be noted, however, that giraffes have been known to gallop at 50 km/h (31 mph).[70] At those speeds, the animal risks breaking a leg or worse, which can be fatal even when the accident occurs in a 'safe' environment, such as a zoo.[71] If it could run, Tyrannosaurus may have been a risk-taker, in much the same way as animals alive today are. Yet estimates of leg bone strength in Tyrannosaurus show that its legs were little stronger, if at all, than those of elephants, which are relatively limited in their top speed and do not ever become 'airborne', as would happen in running.

Walking proponents estimate the top speed of Tyrannosaurus at about 17 km/h (11 mph). This is still faster than the most likely prey species that co-existed with tyrannosaurs; the hadrosaurs and ceratopsians.[72] In addition, some predation advocates claim that tyrannosaur running speed is not important, since it may have been slow but better designed for speed than its probable prey[73] or it may have used ambush tactics to attack faster prey animals.[68]

T. rex mounted skeleton
(Oxford University Museum of Natural History).

The most recent research on Tyrannosaurus locomotion does not specify how fast Tyrannosaurus may have run, but admits that there is little capacity to narrow down speeds further than a range from 17 km/h (11 mph), which would be only walking or slow running, to 40 km/h (25 mph), which would be moderate-speed running. For example, a paper in Nature[72] used a mathematical model (validated by applying it to two living animals, alligators and chickens) to gauge the leg muscle mass needed for fast running (over 25 mph / 40 km/h). They found that proposed top speeds in excess of 40 km/h (25 mph) were unfeasible, because they would require very large leg muscles (more than approximately 40–86% of total body mass.) Even moderately fast speeds would have required large leg muscles. This discussion is difficult to resolve, as it is unknown how large the leg muscles were. If they were smaller, only ~11 mph (18 km/h) walking/jogging might have been possible.[68]

According to Thomas R. Holtz Jr however, it is notable that in terms of any animal as massive as it was (5-7 tons), the tibia/femur and metatarsus/femur ratio of tyrannosaurs are the most gracile known of any animal in the Mesozoic or Cenozoic fossil record.

At the typical size of an adult Tyrannosaurus, gracile limb proportions appear bulky. However, when compared to the hindlimbs of other similarly sized animals, like an elephant (as a modern example), a Triceratops, or Edmontosaurus, the legs of Tyrannosaurus rex are more slender and have relatively longer tibiae and metatarsi.

In relation to other large theropod families, tyrannosaurids had limb proportions that are more gracile. The smaller tyrannosaurids were even more gracile, and the smallest had the same limb proportions to the largest ornithomimids: in terms of measurement, the legs of Alectrosaurus and Gallimimus are identical (Holtz).

Additionally, tyrannosaurids had ornithomimid-like feet, which were smaller and more slender than that of other large theropod families, which would equate to more efficient locomotion as the leg was articulated while the animal was moving.

According to Holtz, with functional morphology as a guide, tyrannosaurids would be better adapted for speed than any other family of large theropod, including allosauroids, megalosauroids and neoceratosaurs. This may not mean that T. rex was capable of the more fantastic speed figures estimated for it, but that it was, for an animal for its size, optimised for speed, and in relevance to the predator/scavenger debate, faster than its prey.[74]

New evidence based on biomechanic computer models suggests Tyrannosaurus had a poor turning circle. According to John Hutchinson, expert on biomechanics at the University of London's Royal Veterinary College in England, Tyrannosaurus would probably have taken one to two seconds to turn only 45° – an amount that humans, being vertically oriented and tail-less, can spin in just a fraction of a second.[75]

History

Henry Fairfield Osborn, president of the American Museum of Natural History, named Tyrannosaurus rex in 1905. The generic name is derived from the Greek words τυραννος (tyrannos, meaning "tyrant") and σαυρος (sauros, meaning "lizard"). Osborn used the Latin word rex, meaning "king", for the specific name. The full binomial therefore translates to "tyrant lizard king," emphasizing the animal's size and perceived dominance over other species of the time.[39]

Earliest finds

The vertebrae named Manospondylus by Cope in 1892 can be considered the first known specimen of Tyrannosaurus rex. Barnum Brown, assistant curator of the American Museum of Natural History, found the second Tyrannosaurus skeleton in Wyoming in 1900. This specimen was originally named Dynamosaurus imperiosus in the same paper in which Tyrannosaurus rex was described.[76] Had it not been for page order, Dynamosaurus would have become the official name. The original "Dynamosaurus" material resides in the collections of the Natural History Museum, London.[77]

Scale model of the never-completed Tyrannosaurus rex exhibit planned for the American Museum of Natural History by H.F. Osborn.

In total, Barnum Brown found five Tyrannosaurus partial skeletons. Brown collected his second Tyrannosaurus in 1902 and 1905 in Hell Creek, Montana. This is the holotype used to describe Tyrannosaurus rex Osborn, 1905. In 1941 it was sold to the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. Brown's fourth and largest find, also from Hell Creek, is on display in the American Museum of Natural History in New York.[41]

Although there are numerous skeletons in the world, only one track has been documented -- at Philmont Scout Ranch in northeast New Mexico. It was discovered in 1983 and identified and documented in 1994.[78]

Notable specimens

Sue the Tyrannosaurus, Field Museum of Natural History, Chicago, showing the forelimbs. The 'wishbone' is between the forelimbs.

Sue Hendrickson, amateur paleontologist, discovered the most complete (more than 90%) and, until 2001 the largest, Tyrannosaurus fossil skeleton known in the Hell Creek Formation near Faith, South Dakota, on August 12, 1990. This Tyrannosaurus, now named "Sue" in her honor, was the object of a legal battle over its ownership. In 1997 this was settled in favor of Maurice Williams, the original land owner, and the fossil collection was sold at auction for USD 7.6 million, making it the most expensive dinosaur skeleton to date. It has now been reassembled and is currently exhibited at the Field Museum of Natural History. Based on a study of 'her' fossilized bones, Sue died at 28 years of age, having reached full size at 19 years of age. Researchers report that a subadult and a juvenile skeleton were found in the same quarry as Sue; this lends evidence to the possibility that tyrannosaurs ran in packs or other groups.[79]

Another Tyrannosaurus, nicknamed "Stan", in honor of amateur paleontologist Stan Sacrison, was found in the Hell Creek Formation near Buffalo, South Dakota, in the spring of 1987. After 30,000 hours of digging and preparing, a 65% complete skeleton emerged. Stan is currently on display in the Black Hills Museum of Natural History Exhibit in Hill City, South Dakota, after an extensive world tour. This tyrannosaur, too, was found to have many bone pathologies, including broken and healed ribs, a broken (and healed) neck and a spectacular hole in the back of its head, about the size of a Tyrannosaurus tooth. Both Stan and Sue were examined by Peter Larson.

In 2001, a 50% complete skeleton of a juvenile Tyrannosaurus was discovered in the Hell Creek Formation in Montana, by a crew from the Burpee Museum of Natural History of Rockford, Illinois. Dubbed "Jane the Rockford T-Rex," the find was initially considered the first known skeleton of the pygmy tyrannosaurid Nanotyrannus but subsequent research has revealed that it is more likely a juvenile Tyrannosaurus.[80] It is the most complete and best preserved juvenile example known to date. Jane has been examined by Jack Horner, Pete Larson, Robert Bakker, Greg Erickson and several other renowned paleontologists, because of the uniqueness of her age. Jane is currently on exhibit at the Burpee Museum of Natural History in Rockford, Illinois.[81][82]

Also in 2001, Dr. Jack Horner discovered a specimen of T. rex around 10% larger than "Sue". Dubbed C. rex (or "Celeste" after Jack's wife), this specimen is currently under study.

In a press release on April 7, 2006, Montana State University revealed that it possessed the largest Tyrannosaurus skull yet discovered. Discovered in the 1960s and only recently reconstructed, the skull measures 59 inches (150 cm) long compared to the 55.4 inches (141 cm) of “Sue’s” skull, a difference of 6.5%.[83][84]

Main article: Tyrannosaurus in popular culture
File:JurassicParkTREX.jpg
Tyrannosaurus from the film Jurassic Park.

Since it was first described in 1905, Tyrannosaurus rex, or "tyrant lizard king" has become the most widely-recognized dinosaur in popular culture. It is the only dinosaur which is routinely referred to by its full scientific name (Tyrannosaurus rex) among the general public, and the scientific abbreviation T. rex has also come into wide usage (commonly misspelled "T-Rex").[2] Robert T. Bakker notes this in The Dinosaur Heresies and explains that a name like "Tyrannosaurus rex is just irresistable to the tongue."[85]

Museum exhibits featuring T. rex are very popular; an estimated 10,000 visitors flocked to Chicago's Field Museum on the opening day of its "Sue" exhibit in 2003.[86] T. rex has appeared numerous times on television and in films, notably The Lost World, King Kong, The Land Before Time, Jurassic Park, and Night at the Museum. A number of books and comic strips, including Calvin and Hobbes, have also featured Tyrannosaurus, which is typically portrayed as the biggest and most terrifying carnivore of all. At least one musical group, the band T. Rex, is named after the species. Tyrannosaurus-related toys, including numerous video games and other merchandise, remain popular. Various businesses have capitalized on the popularity of Tyrannosaurus rex by using it in advertisements.

Footnotes

  1. ^ TYRANNOSAURUS at DinoRuss.com, references are located at [1]
  2. ^ a b c d e f Brochu, C.R. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. Memoirs of the Society of Vertebrate Paleontology. 7: 1-138.
  3. ^ Henderson, D.M. 1999. Estimating the masses and centers of mass of extinct animals by 3-D mathematical slicing. Paleobiology 25: 88–106.
  4. ^ Anderson, J.F., Hall-Martin, A. & Russell, D.A. 1985. Long bone circumference and weight in mammals, birds and dinosaurs. Journal of Zoology 207: 53–61.
  5. ^ a b Bakker, R.T. 1986. The Dinosaur Heresies. New York: Kensington Publishing. 481pp.
  6. ^ a b Farlow, J.O., Smith, M.B., & Robinson, J.M. 1995. Body mass, bone "strength indicator", and cursorial potential of Tyrannosaurus rex. Journal of Vertebrate Paleontology 15: 713-725.
  7. ^ Seebacher, F. 2001. A new method to calculate allometric length-mass relationships iof dinosaurs. Journal of Vertebrate Paleontology 21(1): 51–60.
  8. ^ Christiansen, P. & Fariña, R.A. 2004. Mass prediction in theropod dinosaurs. Historical Biology 16: 85-92.
  9. ^ a b c Erickson, G.M., Makovicky, P.J., Currie, P.J., Norell, M.A., Yerby, S.A., & Brochu, C.A. 2004. Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs. Nature 430: 772-775. Cite error: The named reference "ericksonetal2004" was defined multiple times with different content (see the help page).
  10. ^ a b Currie, P.J., Hurum, J.H., and Sabath, K. 2003. Skull structure and evolution in tyrannosaurid dinosaurs. Acta Palaeontologica Polonica 48(2): 227–234. (download here)
  11. ^ a b c Holtz, T.R. 2004. Tyrannosauroidea. In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.). The Dinosauria (2nd Edition). Berkeley: University of California Press. Pp. 111-136.
  12. ^ a b c Paul, G.S. 1988. Predatory Dinosaurs of the World. New York: Simon & Schuster. 464pp.
  13. ^ a b Holtz, T.R. 1994. The phylogenetic position of the Tyrannosauridae: implications for theropod systematics. Journal of Palaeontology 68(5): 1100-1117.
  14. ^ Maleev, E.A. 1955. [Gigantic carnivorous dinosaurs of Mongolia]. Doklady Akademii Nauk S.S.S.R. 104(4): 634-637. [In Russian]
  15. ^ Rozhdestvensky, A.K. 1965. Growth changes in Asian dinosaurs and some problems of their taxonomy. [Paleontological Journal] 3: 95-109.
  16. ^ Carpenter, K. 1992. Tyrannosaurids (Dinosauria) of Asia and North America. In: Mateer, N. & Chen P. (Eds.). Aspects of Nonmarine Cretaceous Geology. Beijing: China Ocean Press Pp. 250-268. (download here)
  17. ^ Carr, T.D., Williamson, T.E., & Schwimmer, D.R. 2005. A new genus and species of tyrannosauroid from the Late Cretaceous (Middle Campanian) Demopolis Formation of Alabama. Journal of Vertebrate Paleontology 25(1): 119–143.
  18. ^ Hurum, J.H. & Sabath, K. 2003. Giant theropod dinosaurs from Asia and North America: Skulls of Tarbosaurus bataar and Tyrannosaurus rex compared. Acta Palaeontologica Polonica 48(2): 161–190. (download here)
  19. ^ Olshevsky, George (1995). "The origin and evolution of the tyrannosaurids". Kyoryugaku Saizensen [Dino Frontline]. 9–10: 92-119 (9) 75-99 (10).
  20. ^ Carr, T.D. & Williamson, T.E. 2004. Diversity of late Maastrichtian Tyrannosauridae (Dinosauria: Theropoda) from western North America. Zoological Journal of the Linnean Society 142: 479–523.
  21. ^ Gilmore, C.W. 1946. A new carnivorous dinosaur from the Lance Formation of Montana. Smithsonian Miscellaneous Collections 106: 1-19.
  22. ^ Bakker, R.T., Williams, M., & Currie, P.J. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1(5): 1-30.
  23. ^ Carr TD. 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Theropoda). Journal of Vertebrate Paleontology 19: 497–520.
  24. ^ Currie, P.J. 2003. Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontologica Polonica 48(2): 191–226. (download here)
  25. ^ a b Osborn, H.F. 1917. Skeletal adaptations of Ornitholestes, Struthiomimus, Tyrannosaurus. Bulletin of the American Museum of Natural History 35: 733–71.
  26. ^ "T. rex may be in for a name change" by David McCormick. Discovery Channel Canada. 13 June 2000. Accessed 20 July 2006.
  27. ^ International Code of Zoological Nomenclature, Fourth Edition. Article 23.9 - Reversal of Precedence. International Commission on Zoological Nomenclature. 1 January 2000. Accessed 20 July 2006.
  28. ^ "So why hasn't Tyrannosaurus been renamed Manospondylus?" by Mike Taylor. 27 August 2002. Accessed 20 July 2006.
  29. ^ a b Horner, J.R. & Padian, K. 2004. Age and growth dynamics of Tyrannosaurus rex. Proceedings of the Royal Society of London B 271: 1875-1880.
  30. ^ a b Schweitzer, M.H., Wittmeyer, J.L., & Horner, J.R. 2005. Gender-specific reproductive tissue in ratites and Tyrannosaurus rex. Science 308: 1456-1460.
  31. ^ a b Erickson, G.M., Currie, P.J., Inouye, B.D., & Winn, A.A. 2006. Tyrannosaur life tables: an example of nonavian dinosaur population biology. Science 313: 213-217.
  32. ^ Carpenter, K. 1990. Variation in Tyrannosaurus rex. In: Carpenter, K. & Currie, P.J. (Eds.). Dinosaur Systematics: Approaches and Perspectives. New York: Cambridge University Press. Pp. 141-145. (download here)
  33. ^ Larson, P.L. 1994. Tyrannosaurus sex. In: Rosenberg, G.D. & Wolberg, D.L. Dino Fest. The Paleontological Society Special Publications. 7: 139-155.
  34. ^ Erickson, G.M., Lappin, A.K., & Larson, P.L. 2005. Androgynous rex. The utility of chevrons for determining the sex of crocodilians and non-avian dinosaurs. Zoology 108: 277-286.
  35. ^ Schweitzer, M.H., Elsey, R.M., Dacked, C.G., Horner. J.R., & Lamm, E.-T. 2007. Do egg-laying crocodilian (Alligator mississippiensis) archosaurs form medullary bone? Bone 40 (4): 1152-1158. doi:10.1016/j.bone.2006.10.029
  36. ^ Leidy, J. 1865. Memoir on the extinct reptiles of the Cretaceous formations of the United States. Smithsonian Contributions to Knowledge. 14: 1-135.
  37. ^ "Tyrannosaurus" American Museum of Natural History. (20 July 2006).
  38. ^ a b Newman, B.H. 1970. Stance and gait in the flesh-eating Tyrannosaurus. Biological Journal of the Linnean Society. 2: 119-123.
  39. ^ a b Osborn, H.F. 1905. Tyrannosaurus and other Cretaceous carnivorous dinosaurs. Bulletin of the American Museum of Natural History 21: 259-265. (download here)
  40. ^ Lambe, L.M. 1914. On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of the skull of Stephanosaurus marginatus from the same horizon. Ottawa Naturalist 27: 129-135.
  41. ^ a b c Horner, J.R. & Lessem, D. 1993. The Complete T. rex: How Stunning New Discoveries Are Changing Our Understanding of the World's Most Famous Dinosaur. New York: Simon & Schuster. 235pp.
  42. ^ Osborn, H.F. 1906. Tyrannosaurus, Upper Cretaceous carnivorous dinosaur (second communication). Bulletin of the American Museum of Natural History. 22: 281-296. (download here)
  43. ^ Carpenter, K. & Smith, M.B. 2001. Forelimb osteology and biomechanics of Tyrannosaurus. In: Tanke, D.H. & Carpenter, K. (Eds.). Mesozoic Vertebrate Life. Bloomington: Indiana University Press. Pp. 90-116. (download here)
  44. ^ Schweitzer M.H., Wittmeyer J.L., Horner J.R., Toporski J.B. 2005. Soft Tissue Vessels and Cellular Preservation in Tyrannosaurus rex. Science 307: 1952-1955.
  45. ^ Fields, H. "Dinosaur Shocker". Smithsonian Magazine Online. Retrieved 2006-05-01. {{cite web}}: Cite has empty unknown parameter: |accessyear= (help)
  46. ^ Rincon, Paul. "Protein links T. rex to chickens". {{cite web}}: Cite has empty unknown parameter: |accessyear= (help); Unknown parameter |accessmonthday= ignored (help)
  47. ^ Yesterday's T. Rex is today's chicken. USA Today, APR. 13, 2007.
  48. ^ Xu X., Norell, M.A., Kuang X., Wang X., Zhao Q., & Jia C. 2004. Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids. Nature 431: 680-684.
  49. ^ Bakker, R.T. 1968. The superiority of dinosaurs. Discovery 3: 11-22.
  50. ^ Bakker, R.T. 1972. Anatomical and ecological evidence of endothermy in dinosaurs. Nature 238: 81-85.
  51. ^ Barrick, R.E. & Showers, W.J. 1994. Thermophysiology of Tyrannosaurus rex: Evidence from oxygen isotopes. Science 265: 222-224.
  52. ^ Trueman, C., Chenery, C., Eberth, D.A. & Spiro, B. 2003. Diagenetic effects on the oxygen isotope composition of bones of dinosaurs and other vertebrates recovered from terrestrial and marine sediments. Journal of the Geological Society, London 160: 895–901.
  53. ^ Barrick, R.E. & Showers, W.J. 1999. Thermophysiology and biology of Giganotosaurus: comparison with Tyrannosaurus. Palaeontologia Electronica 2 (2): 22pp.
  54. ^ Barrick, R.E., Stoskopf, M. & Showers, W.J. 1997. Oxygen isotopes in dinosaur bones. In: Farlow, J.O. & Brett-Surman, M. (Eds.). The Complete Dinosaur. Bloomington: Indiana University Press. Pp. 474-490.
  55. ^ Paladino, F.V., Spotila, J.R., & Dodson, P. 1997. A blueprint for giants: modeling the physiology of large dinosaurs. In: Farlow, J.O. & Brett-Surman, M. (Eds.). The Complete Dinosaur. Bloomington: Indiana University Press. Pp. 491-504.
  56. ^ Chinsamy, A. & Hillenius, W.J. 2004. Physiology of nonavian dinosaurs. In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.). The Dinosauria (2nd Edition). Berkeley: University of California Press. Pp. 643-659.
  57. ^ Horner, J.R., (1994). Steak knives, beady eyes, and tiny little arms (a portrait of Tyrannosaurus as a scavenger). The Paleontological Society Special Publication 7: 157-164.
  58. ^ a b Walters, M., Paker, J. (1995). Dictionary of Prehistoric Life. Claremont Books. ISBN 1-85471-648-4.
  59. ^ Farlow, J. O. and Holtz, T. R. Jr. 2002. The fossil record of predation in dinosaurs. pp. 251–266, in M. Kowalewski and P. H. Kelley (eds.), The Fossil Record of Predation. The Paleontological Society Papers 8.
  60. ^ Dorey, M. (1997). Tyrannosaurus. Dinosaur Cards. Orbis Publishing Ltd. D36045907.
  61. ^ Stevens, K.A. (2006) Binocular vision in theropod dinosaurs. Journal of Vertebrate Paleontology 26(2):321-330
  62. ^ Tanke, D.H. & Currie, R.J. Head-Biting Behavior in Theropod Dinosaurs: Paleopathological Evidence. May 2000. Gaia 15
  63. ^ Goldstone, E. (1997). Injury & Disease, Part 3. Dinosaur Cards. Orbis Publishing Ltd. D36045009.
  64. ^ Erickson, G. M., and Olson, K. H. (1996). "Bite marks attributable to Tyrannosaurus rex: preliminary description and implications." Journal of Vertebrate Paleontology, 16(1): 175-178.
  65. ^ Carpenter, K. (2000). "Evidence of predatory behavior by carnivorous dinosaurs." Gaia, 15: 135-144.
  66. ^ Fowler, D. W., and Sullivan, R. M. (2006). "A ceratopsid pelvis with toothmarks from the Upper Cretaceous Kirtland Formation, New Mexico: evidence of late Campanian tyrannosaurid feeding behavior." New Mexico Museum of Natural History and Science Bulletin, 35: 127-130.
  67. ^ "The bigger they come, the harder they fall" New Scientist, October 7 1995, p. 18.
  68. ^ a b c Hajdul, R. (1997). Tendons. Dinosaur Cards. Orbis Publishing Ltd. D36044311.
  69. ^ Hecht, J. (1998). The deadly dinos that took a dive. New Scientist 2130.
  70. ^ "Giraffe". WildlifeSafari.info. Retrieved 2006-04-29.
  71. ^ "The History of Woodland Park Zoo - Chapter 4". Retrieved 2006-04-29.
  72. ^ a b Hutchinson, J. R. and Garcia, M. (2002). Tyrannosaurus was not a fast runner. Nature 415: 1018-1021
  73. ^ "Unearthing T. rex: T. rex In-Depth: Traits (See above)". {{cite web}}: Unknown parameter |accessmonthday= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  74. ^ Thomas R. Holtz, Jr. "Gracility and Speed of T. rex". Dinosauria online.
  75. ^ "Tyrannosaurus had poor turning circle" Cosmos magazine
  76. ^ Osborn, H. F. 1905.Tyrannosaurus and other Cretaceous carnivorous dinosaurs. Bulletin of the American Museum of Natural History 21;259-265
  77. ^ White, S. (1997). Tyrannosaurus. Dinosaur Cards. Orbis Publishing Ltd. D36046009.
  78. ^ Online guide to the continental Cretaceous-Tertiary boundary in the Raton basin, Colorado and New Mexico
  79. ^ Guinness World Records Ltd. (2003). 2003 Guinness World Records. pg 90.
  80. ^ Currie, P. J., Hurum, J. H., and Sabath, K. 2003. Skull structure and evolution in tyrannosaurid dinosaurs. Acta Palaeontologica Polonica 48: 227-234
  81. ^ Croucher, B. (1997). Beast of the Badlands. Dinosaur Cards. Orbis Publishing Ltd. D36045407.
  82. ^ Visit Jane.com. Official musuem website.
  83. ^ "Museum unveils world's largest T-rex skull". {{cite web}}: Unknown parameter |accessmonthday= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  84. ^ Ryan, M. J. "New Biggest T-rex Skull". {{cite web}}: Unknown parameter |accessmonthday= ignored (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
  85. ^ Robert T. Bakker, The Dinosaur Heresies: New Theories Unlocking the Mystery of the Dinosaurs and their Extinction (New York: William Morrow Company, 1986) page 464.
  86. ^ Guinness World Records Ltd. 2003. 2003 Guinness World Records. p. 90.

References

Wikimedia Commons has media related to Tyrannosaurus.
Wikibooks has a book on the topic of: Wikijunior Dinosaurs/T-Rex

Template:Link FA

Retrieved from "https://en.wikipedia.org/enwiki/w/index.php?title=Tyrannosaurus&oldid=152452399"