Tyrannosaurus (, meaning 'tyrant lizard') is a genus of theropod dinosaur. The famous species Tyrannosaurus rex ('rex' meaning 'king' in Latin), commonly abbreviated to T. rex, is a fixture in popular culture around the world. It lived throughout what is now western North America, with a much wider range than other tyrannosaurids. Fossils of T. rex are found in a variety of rock formations dating to the last three million years of the Cretaceous Period, approximately 68 to 65 million years ago; it was among the last non-avian dinosaurs to exist prior to the Cretaceous?Tertiary extinction event.

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, though unusually powerful for their size, and bore two primary digits, along with a possible third vestigial digit. 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 13 meters (43 ft) in length,^[1] up to 4 meters (13 ft) tall at the hips,^[2] and up to 6.8 metric tons (7.5 short tons) in weight.^[3] By far the largest carnivore in its environment, T. rex may have been an apex predator, preying upon hadrosaurs and ceratopsians, although some experts have suggested it was primarily a scavenger.

More than 30 specimens of T. rex have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. 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 subjects of debate. Its taxonomy is also controversial, with some scientists considering Tarbosaurus bataar from Asia to represent a second species of Tyrannosaurus and others maintaining Tarbosaurus as a separate genus. Several other genera of North American tyrannosaurids have also been synonymized with Tyrannosaurus.

Description

Various specimens of Tyrannosaurus rex with a human for scale.

Size comparison of selected giant theropod dinosaurs, Tyrannosaurus in purple.

The largest known T. rex skulls measure up to 1.5 meters (5 ft) in length. Large fenestrae (openings) in the skull reduced weight and provided areas for muscle attachment, as in all carnivorous theropods. But in other respects Tyrannosaurus? skull was significantly different from those of large non-tyrannosauroid theropods. It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision.^[13] The skull bones were massive and the nasals and some other bones were fused, preventing movement between them; but many were pneumatized (contained a "honeycomb" of tiny air spaces) which may have made the bones more flexible as well as lighter. These and other skull-strengthening features are part of the tyrannosaurid trend towards an increasingly powerful bite, which easily surpassed that of all non-tyrannosaurids.^[14][15][16] The tip of the upper jaw was U-shaped (most non-tyrannosauroid carnivores had V-shaped upper jaws), which increased the amount of tissue and bone a tyrannosaur could rip out with one bite, although it also increased the stresses on the front teeth.^[17][18]

Life restoration of a Tyrannosaurus rex.

Classification

T. rex head reconstruction at the Oxford University Museum of Natural History.

In 1955, Soviet paleontologist Evgeny Maleev named a new species, Tyrannosaurus bataar, from Mongolia.^[24] By 1965, this species had been renamed Tarbosaurus bataar.^[25] Despite the renaming, many phylogenetic analyses have found Tarbosaurus bataar to be the sister taxon of Tyrannosaurus rex,^[23] and it has often been considered an Asian species of Tyrannosaurus.^[17][26][27] 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.^[28] 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.^[22]

Other tyrannosaurid fossils found in the same formations as T. rex were originally classified as separate taxa, including Aublysodon and Albertosaurus megagracilis,^[18] the latter being named Dinotyrannus megagracilis in 1995.^[29] However, these fossils are now universally considered to belong to juvenile T. rex.^[30] 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,^[31] but was later referred to a new genus, Nanotyrannus.^[32] Opinions remain divided on the validity of N. lancensis. Many paleontologists consider the skull to belong to a juvenile T. rex.^[33] 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.^[23][34]

Manospondylus

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.

In June 2000, 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.^[36] 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?"^[37] 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").^[38]

Paleobiology

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.

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 (1,300 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).^[3] Another recent histological study performed by different workers corroborates these results, finding that rapid growth began to slow at around 16 years of age.^[39] This sudden change in 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.^[40] Further study indicates an age of 18 for this specimen.^[41] Other tyrannosaurids exhibit extremely similar growth curves, although with lower growth rates corresponding to their lower adult sizes.^[42]

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.^[42]

Sexual dimorphism

Tyrannosaurus skeleton casts mounted in a mating position, Jurassic Museum of Asturies.

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.^[45] 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.^[1]

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.^[40] 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.^[46]

Posture

Outdated reconstruction (by Charles R. Knight), showing 'tripod' pose.

Replica at Senckenberg Museum, showing modern view of posture.

Arms

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

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.^[55] 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.^[56] 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.^[57] Research on some of the tissues involved has suggested that birds are closer relatives to tyrannosaurs than other modern animals.^[58]

In 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."^[59]

Subsequent studies in April 2008 confirmed the close connection of T. rex to modern birds. Postdoctoral biology researcher Chris Organ at Harvard University announced, "With more data, they would probably be able to place T. rex on the evolutionary tree between alligators and chickens and ostriches." Co-author John M. Asara added, "We also show that it groups better with birds than modern reptiles, such as alligators and green anole lizards."^[60]

The presumed soft tissue was called into question by Thomas Kaye of the University of Washington and his co-authors in 2008. They contend that what was really inside the tyrannosaur bone was slimy biofilm created by bacteria that coated the voids once occupied by blood vessels and cells.^[61] The researchers found that what previously had been identified as remnants of blood cells, because of the presence of iron, were actually framboids, microscopic mineral spheres bearing iron. They found similar spheres in a variety of other fossils from various periods, including an ammonite. In the ammonite they found the spheres in a place where the iron they contain could not have had any relationship to the presence of blood.^[62]

Skin and feathers

Tyrannosaurus baby covered with downy feathers

Thermoregulation

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.^[65][66] Tyrannosaurus rex itself was claimed to have been endothermic ("warm-blooded"), implying a very active lifestyle.^[6] 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.^[39]

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.^[67] 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).^[68] 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).^[69] Ornithischian dinosaurs also showed evidence of homeothermy, while varanid lizards from the same formation did not.^[70] Even if Tyrannosaurus rex does exhibit evidence of homeothermy, it does not necessarily mean that it was endothermic. Such thermoregulation may also be explained by gigantothermy, as in some living sea turtles.^[71][72]

Footprints

The probable Tyrannosaurus rex footprint from New Mexico.

A second footprint that may have been made by a Tyrannosaurus was first reported in 2007 by British paleontologist Phil Manning, from the Hell Creek Formation of Montana. This second track measures 76 cm (30 in) long, shorter than the track described by Lockley and Hunt. Whether or not the track was made by Tyrannosaurus is unclear, though Tyrannosaurus and Nanotyrannus are the only large theropods known to have existed in the Hell Creek Formation. Further study of the track (a full description has not yet been published) will compare the Montana track with the one found in New Mexico.^[74]

Locomotion

A sequence of sauropod footprints. No such sequence has yet been reported for tyrannosaurs, making gait and speed estimates difficult.

Tyrannosaurus may have been slow to turn, possibly taking one to two seconds to turn only 45° ? an amount that humans, being vertically oriented and tail-less, can spin in a fraction of a second.^[75] The cause of the difficulty is rotational inertia, since much of Tyrannosaurus? mass was some distance from its center of gravity (like a human carrying a heavy timber) - although it might have reduced the average distance by arching its back and tail and pulling its head and forelimbs close to its body (rather like the way an ice skater pulls his or her arms closer in order to spin faster).^[76]

Scientists have produced a wide range of maximum speed estimates, mostly around 11 meters/second (25 mph), but a few as low as 5-11 meters/second (12-25 mph), and a few as high as 20 meters/second (45 mph). Researchers have to rely on various estimating techniques because, while there are many tracks of very large theropods walking, so far none have been found of very large theropods running - and this absence may indicate that they did not run.^[77] Scientists who think that Tyrannosaurus was able to run 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).^[78]

Skeletal anatomy of a T. rex right leg.

Christiansen (1998) estimated that the leg bones of Tyrannosaurus were not significantly stronger than those of elephants, which are relatively limited in their top speed and never actually run (there is no airborne phase), and hence proposed that the dinosaur's maximum speed would have been about 11 meters/second (about 24 mph), which is about the speed of a human sprinter. But he also noted that such estimates depend on many dubious assumptions.^[80]

Farlow and colleagues (1995) have argued that a 6-8 ton Tyrannosaurus would have been critically or even fatally injured if it had fallen while moving quickly, since its torso would have slammed into the ground at a deceleration of 6 g (six times the acceleration due to gravity, or about 60 meters/s²) and its tiny arms could not have reduced the impact.^[7][81] However, giraffes have been known to gallop at 50 km/h (31 mph), despite the risk that they might break a leg or worse, which can be fatal even in a "safe" environment such as a zoo.^[82][83] Thus it is quite possible that Tyrannosaurus also moved fast when necessary and had to accept such risks.^[84][85]

Foot of a Tyrannosaurus rex.

A study in 2007 used computer models to estimate running speeds, based on data taken directly from fossils, and claimed that T. rex had a top running speed of 8 meters per second (18 mph). An average professional football (soccer) player would be slightly slower, while a human sprinter can reach 12 m/s (27 mph). Note that these computer models predict a top speed of 17.8 m/second (about 45 mph) for a 3 kilogram (7 lb) Compsognathus^[88] This may be a preliminary version of Sellers, W. I., Manning, P.L., Crompton, R.H. and Codd, J.R., . (2007), "Exploring elastic energy storage effects in bipedal locomotion using evolutionary robotics", Journal of Biomechanics, in-review^[89] (probably a juvenile individual).^[90]

Those who argue that Tyrannosaurus was incapable of running estimate the top speed of Tyrannosaurus at about 17 km/h (11 mph). This is still faster than its most likely prey species, hadrosaurids and ceratopsians.^[87] In addition, some advocates of the idea that Tyrannosaurus was a predator (see below) claim that tyrannosaur running speed is not important, since it may have been slow but still faster than its probable prey.^[91] However, Paul and Christiansen (2000) argued that at least the later ceratopsians had upright forelimbs and the larger species may have been as fast as rhinos.^[92] Healed Tyrannosaurus bite wounds on ceratopsian fossils are interpreted as evidence of attacks on living ceratopsians (see below). If the ceratopsians that lived alongside Tyrannosaurus were fast, that casts doubt on the argument that Tyrannosaurus did not have to be fast to catch its prey. Alternatively, perhaps Tyrannosaurus used ambush tactics to attack faster prey animals.^[78] The debate about Tyrannosaurus? speed seems far from finished.

Feeding strategies

Profile view of a Tyrannosaurus skull (AMNH 5027).

Noted hadrosaur expert Jack Horner is currently the major advocate of the idea that Tyrannosaurus was exclusively a scavenger and did not engage in active hunting at all.^[96][52][97] Horner has presented several arguments to support the pure scavenger hypothesis:

Cast of a Tyrannosaurus rex braincase at the Australian Museum, Sydney.

• Tyrannosaurs had large olfactory bulbs and olfactory nerves (relative to their brain size). These suggest a highly developed sense of smell which could sniff out carcasses over great distances, as modern vultures do. Opponents of the pure scavenger hypothesis have used the example of vultures in the opposite way, arguing that the scavenger hypothesis is implausible because the only modern pure scavengers are large gliding birds, which use their keen senses and energy-efficient gliding to cover vast areas economically.^[98] However, researchers from Glasgow concluded that an ecosystem as productive as the current Serengeti would provide sufficient carrion for a large theropod scavenger, although the theropod might have had to be cold-blooded in order to get more calories from carrion than it spent on foraging (see Warm-bloodedness of dinosaurs). They also suggested that modern ecosystems like Serengeti have no large terrestrial scavengers because gliding birds now do the job much more efficiently, while large theropods did not face competition for the scavenger ecological niche from gliding birds.^[99]
• Tyrannosaur teeth could crush bone, and therefore could extract as much food (bone marrow) as possible from carcass remnants, usually the least nutritious parts. Karen Chin and colleagues have found bone fragments in coprolites (fossilized dung) that they attribute to tyrannosaurs, but point out that a tyrannosaur's teeth were not well adapted to systematically chewing bone like hyenas do to extract marrow.^[100]
• Since at least some of Tyrannosauruss potential prey could move quickly, evidence that it walked instead of ran could indicate that it was a scavenger.^[96][101] On the other hand, recent analyses suggest that Tyrannosaurus, while slower than large modern terrestrial predators, may well have been fast enough to prey on large hadrosaurs and ceratopsians.^[87][91] It may also have used ambush tactics to attack faster prey animals.^[78]

The eye-sockets of T. rex faced mainly forwards, giving it good binocular vision.

At the site where the very large tyrannosaur named Sue was found, a skeleton of the hadrosaurid Edmontosaurus annectens was also found, with healed tyrannosaur-inflicted damage on its tail vertebrae. The fact that the damage seems to have healed suggests that the Edmontosaurus survived a tyrannosaur's attack on a living target, i.e. the tyrannosaur had attempted active predation.^[102][103] A Triceratops was found in Mexico found with bite marks on its ilium. These were also inflicted by a tyrannosaur and they too appear healed, indicating active predation by the tyrannosaur.^[104] Tyrannosaurus also had a bite force estimated at between 183,000 and 235,000 N,^[16] 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.^[106]

Some researchers argue that if Tyrannosaurus were a scavenger, another dinosaur had to be the top predator in the Amerasian Upper Cretaceous. Top prey was 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.^[101] Most paleontologists accept that Tyrannosaurus was both an active predator and a scavenger.

History

Skeletal restoration by William D. Matthew from 1905, which was the first reconstruction of Tyrannosaurus rex ever published^[107]

Earliest finds

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

Barnum Brown, assistant curator of the American Museum of Natural History, found the first partial skeleton of T. rex in eastern Wyoming in 1900. H. F. Osborn originally named this skeleton Dynamosaurus imperiosus in a paper in 1905. Brown found another partial skeleton in the Hell Creek Formation in Montana in 1902. Osborn used this holotype to describe Tyrannosaurus rex in the same paper in which D. imperiosus was described.^[109] 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.^[110]

In total, Brown found five Tyrannosaurus partial skeletons. In 1941, Brown's 1902 find 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.^[52]

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.^[111]

Notable specimens

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

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.

"Jane" at the Burpee Museum in Rockford, Illinois

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%.^[118][119]

Appearances in popular culture

Since it was first described in 1905, Tyrannosaurus rex 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").^[1] Robert T. Bakker notes this in The Dinosaur Heresies and explains that a name like "Tyrannosaurus rex is just irresistible to the tongue."^[6]

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.^[120] T. rex has appeared numerous times on television and in films, notably (in chronological order) The Lost World, King Kong, The Land Before Time, Jurassic Park, Toy Story, Toy Story 2, Walking with Dinosaurs, and Night at the Museum, among many others. 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.

References

See also

• - a good survey of research

External links

• Tyrannosauridae "Tree of Life" page, very comprehensive survey by major authority Tom Holtz.
• ''Tyrannosaurus'' in the Dino Directory
• Sue's homepage
• Stan's homepage
• Tree of Life discussing Tyrannosauridae "Tree of Life" page, very comprehensive survey by major authority Tom Holtz.
• Unearthing ''Tyrannosaurus rex''
• ''T.rex'' juvenile Jane
• NBCI's Taxonomy Browser
• Cretaceous Hell Creek Faunal Facies is an example of one tyrannosaur environment, in the Hell Creek Formation of Montana
• Bristol University study on bite forces of predators
• Museum of Unnatural Mystery ? Bite force etc. of ''T. rex''
• Stanford University on bite force of ''T. rex''
• How Tyrannosaurus might have had sex
• Recent Discovery of Soft Tissue

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