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T-rex
Temporal range: Late Cretaceous
Tyrannosaurus reconstruction by Fred Wierum
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Clade: Dinosauria
Order: Saurischia
Family: Tyrannosauridae
Genus: Tyrannosaurus
Osborn, 1905
Species: T. rex
Type species
Tyrannosaurus rex
Osborn et al., 1905
Synonyms

Genus synonymy

  • Manospondylus (Cope, 1892)
  • Dynamosaurus (Osborn, 1905)
  • Nanotyrannus (Bakker, Williams and Currie, 1988)
  • Stygivenator? (Olshevsky, 1995)

Species synonymy

Tyrannosaurus rex (Greek for "Tyrant Lizard King"), more commonly referred to as the "T-rex" (colloquial: "T-rex"), is a species of tyrannosaurian theropod dinosaur that flourished during the Maastrichtian age of the Late Cretaceous epoch, 68-66 million years ago.

Ever since it's discovery in 1900, Tyrannosaurus has become one of if not the popular of its kind; as over 50 indivuals of this taxon have been unearthed. The largest, most complete specimen of the T-rex was nicknamed "Sue" (located at Chicago's Field Museum of Natural History, which is roughly 90% complete), measuring approximately 12.3 meters (40 feet) in length, around 3.5 meters (eleven feet) high at the hips, and 8.46 tons (7.67 tonnes) in weight, making it among the largest terrestrial predators to ever exist.

A diagram showing the individual body size and types of different Tyrannosaurus specimens.

Tyrannosaurus lived throughout present-day western North America, within a depositional fossil formation known as Hell Creek. Tyrannosaurus was of a much broader geographical range than other tyrannosaurids, including Montana, Wyoming, South and North Dakota, Colorado, Texas, and Saskatchewan. It was among the last non-avian dinosaurs to live prior to the K-T mass extinction event.

Discovery and History

Although teeth and indeterminate fragments had been discovered prior, in 1892, paleontologist Edward Drinker Cope described the first known T-rex skeleton, which he dubbed "Manospondylus gigas" (Greek for "Giant Thin Vertabrea"). The specimen was originally believed to have belong to that of a ceratopsian, but is currently considered Nomen oblitum.

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

When Barnum Brown and his crew made an expedition to Montana in 1900, they stumbled upon the first partial T-rex skeleton, and then a second one in 1902 that would be properly represented as the neotype specimen. In 1905, Henry Fairfield Osborn named the skeleton "Tyrannosaurus rex", which is the name that has prevailed since. Many more indivuals of the dinosaur have been discovered since, including ones that are nearly complete, show numerous ontogenetic stages, skin impressions, and even soft tissue.

Brown's 1902 discovery of "Dynamosaurus imperiosus," has also been synonymized with Tyrannosaurus rex, as the Dynamosaurus holotype was reported showing osteoderms that belonged to Ankylosaurus, which the T-rex lived alongside with in Late-Cretacous North America. Tarbosaurus was also, at one point, categorized as a a second Asian species of Tyrannosaurus. However, despite similarities between the two, there were enough distinct traits between the two taxa that Tarbosaurus is now usually referred to as its own species, Tarbosaurus bataar (although some scientists classify it as a junior synonym).

Description

The skeletal reconstruction of Tyrannosaurus when it was first described, depicting the classic upright tail-dragging stance.

Tyrannosaurus rex was one of, if not the terrestrial carnivores of all time. The largest known specimen, RSM P2523.8 (AKA "Scotty"), measures 12.9 meters (42 feet) in length, stood four meters (13 feet) tall at the hips, and weighed nine tons (eight tonnes), although most fully-grown adults would have averaged only 6-8 tons (5-7 tonnes) in weight and 11-12 meters (36-39 feet) in length. Despite it's massive size, theropods such as Spinosaurus and Giganotosaurus may have potentially surpassed T-rex in both height and length. It is believed that Sue and Scotty are among the oldest of their kind, currently known at 28 years old or more (in comparison, the average T-rex lifespan is estimated at about 25 years old).

T. rex's skull was capable of growing upto five feet (1.5 meters) in length and was extremely robustly-built. The base was significantly wider than the snout, providing it with excellent binocular and steroscopic vision, even greater than that of a human as studies suggest. Its mouth was broad compared to that of most other theropods and resembled a U-shape, increasing the amount of surface area it could chomp down on with a single bite. The skull retained several openings in it, known as "fenestra", that lightened the head and likely held soft tissue such as muscle or blood vessels, and the fenestra on top of its head may have served as a cooling mechanism, as seen in crocodiles. Additionally, The T-rex's jaws averaged four feet (1.2 meters) in length and were very muscular, compensating for the animal's devastating biting strength. Analysis has shown that Tyrannosaurus was capable of opening its jaws upto approximately 63-80 degrees wide, maximum.

A recent, up to date skeletal reconstruction of the Tyrannosaurus specimen "Sue". Artwork by RandomDinos on DeviantArt.

The neck of the T-rex formed a natural S-shaped curve, similar to that of other theropods, but was relatively short, and would have been immensly robust in order to support its massive head. Tyrannosaur's often-ridiculed forelimbs were only around the size of an adult human's arms, but were anchored to powerful muscles (the T-rex's arms were capable of bench pressing 400 pounds each), and, unlike dinosaurs such as Carnotaurus and its relatives, were not vestigial and would have had some use in life, although the exact purpose for them is not entirely known. Unlike more basal theropods, Tyrannosaurus' hands bore only two usable digits that were tipped with sharp claws, the third being undeveloped and was to small to have shown through the skin. In contrast to the forelimbs, the hind limbs were among the longest in proportion to body size of any theropod and incredibly muscular in order to support the animal's massive bulk. Its feet resembled those of terrestrial birds, with three longer toes that would have impacted the ground, and one vestigial hallux "dewclaw" that would have never touched the Earth; each toe was tipped with massive slightly hoof-esque claws.

A feathered reconstruction of Tyrannosaurus. Artwork by RJ Palmer.

The tail was long and heavy, occasionally containing over 40 vertebrae in order to balance the large head and torso. To compensate for it's immense size, many bones throughout the skeleton were hollow (similar to birds and other theropods), reducing its weight without major loss of strength. The torso was wide and deep, resembling "barrel-chest". This body would have supported most of the animal's internal organs, with aid from its gastralia (belly ribs). Since Tyrannosaurus was a saurischian dinosaur, the pubis in the hips would have pointed forward and away from the backward-facing ischium.

The teeth of T. rex displayed some heterodonty (differences in shape). The teeth in the premaxilla (front upper jaw) were relatively small and closely packed, D-shaped in cross-section, possessed reinforcing ridges on the rear surface, were incisiform (their tips were chisel-like blades) and curved backwards, which all would have decreased the risk of the teeth breaking when animal bit and pulled. The remaining teeth were robust, like "lethal bananas" rather than daggers as seen in more basal theropods, more widely spaced and also possessed reinforcing roots. The teeth in the middle of the maxilla were the largest in its jaws; the largest Tyrannosaurus tooth discovered currently was recorded as measuring 30.5 cm (12 inches) in length, including the root, making it the largest tooth of any carnivorous dinosaur and easily one of the largest teeth in the animal kingdom.

Taxonomy

Various members of tyrannosauridae.

Tyrannosaurus is the type genus of the superfamily Tyrannosauroidea, the family Tyrannosauridae, and the subfamily Tyrannosaurinae, making it the standard by which paleontologists decide whether to include other described species within the same group. Its closest relatives currently appear to be the North American Daspletosaurus and the Asian Tarbosaurus, the latter of which is considered to be the sister taxon to Tyrannosaurus. In fact, recent studies seem to suggest that since Tarbosaurus and Tyrannosaurus share so many characteristics, it is proposed that perhaps the direct ancestor to T. rex had migrated from Asia to North America over the Bering Strait and acted as an invasive species, using its larger size to wipe out its native North American relatives such as Albertosaurus. Tyrannosaurids were once commonly thought to be descendants of earlier large theropods like the carnosaurs, although more recently they have been reclassified to fit within the generally smaller coelurosaur family tree.

The anatomy of tyrannosaurs, showing the variety of skeletal and cranial morphology in the group from Brusatte et al (2010).

The earliest known tyrannosauroids were small and covered in feathers. They were most certainly not the apex predators of their time, as they were in the shadow of the much larger allosauroids. The earliest of these species, Proceratosaurus, lived in Europe during the Jurassic Period 167 million years ago. As time passed on and the carnosaurs went extinct, the tyrannosauroids took the mantel as top predators in their ecosystem and evolved to be bigger as they traveled west into Asia and eventually North America. Perhaps the most well known of these basal tyrannosauroids is Yutyrannus, which is famous for being the largest animal known to have been covered in feathers. This lead to the idea that perhaps Tyrannosaurus and its closest relatives were feathered as well. However, a study in 2017 with skin impressions from more derived tyrannosaurids, including T. rex itself, show that it was in fact covered in small scales instead.

The Tyrannosauroidea family tree showing geographical and temporal range.

In 1946, a small tyrannosaur skull from Hell Creek was found by Charles W. Gilmore that was dubbed as a species of Gorgosaurus. However upon further inspection, the skull was found to be too distinct to be a species of Gorgosaurus and was thus given its own name, Nanotyrannus lancensis. However, this genus too would come under suspicion as to whether it could be considered its own taxon when it was noted that the specimen showed signs of immaturity, and was then hypothesized to instead be a juvenile of the only other tyrannosaur known from Hell Creek, Tyrannosaurus rex. This hypothesis would be further suspected to be the case with the discovery of BMRP 2002.4.1 (AKA Jane), a 6 m (20 ft) tyrannosaur from Montana whose skull showed similar traits to the Nanotyrannus holotype. When histology was done on Jane, it was found that its bones didn't show skeletal maturity and the study came to the conclusion that Jane was in fact a juvenile Tyrannosaurus, making Nanotyrannus a Nomen dubnium.

Artist's illustration depicting a young Tyrannosaurus as a fleet-footed ambush predator.

However, cases have been made that perhaps Jane and the holotype skull are in fact juveniles but might just belong to a completely different species of tyrannosaur that just hasn't been found yet in Hell Creek, a similar case to Alioramus in the Nemegt Formation, and would therefore keep Nanotyrannus as a valid taxon. The Nano-morphs follow a similar pattern of characteristics including a long, narrow snout, less binocular vision, blade-like teeth, long, slender hind limbs, a more slim body plan in general compared to its potential adult counterparts, and 15 or more teeth in its lower jaw compared to the typical 12-13 found in adult T. rex.

Paleobiology

Tyrannosaurus rex was one of the largest of the theropod dinosaurs and easily the largest predator in its environment. It had a massive skull with reinforced banana-like teeth. Recent studies have estimated that T. rex was capable of biting down with 64,000 N (over 6 tonnes) of force, making it one of the most powerful bites ever known. This amount of force was capable of not only piercing, but completely shattering bone and armor, which would explain why its teeth were so robust, reinforced, and relatively blunt, used for attacking large prey, and crushing smaller prey like Ornithomimids. It likely formed such devastating features in order to prey on well-defended herbivores such as the three-horned Triceratops and Torosaurus, which would in turn evolve more defenses and make a vicious cycle of an evolutionary arm's race. While it was originally hypothesized that T. rex might have had flexible parts of its skull like modern relatives such as parrots and lizards, recent studies involving 3D imaging compared stresses on its head revealed that the bones in its skull would instead have been fused like a crocodile in order to reinforce it and keep it from breaking apart due to the massive amount of force its jaws could deliver.

In life Tyrannosaurus would have had eyes the size of softballs and were capable of seeing long distances with very good depth due to them being forward-facing, giving it binocular vision. CAT-Scans of the skull have revealed that much of the brain was dedicated to its sense of smell, giving T. rex one of the strongest senses known in any modern or extinct taxa. The structure of bones around its ear would have been well suited to picking up low-frequency sounds like modern-day elephants do, indicating that T. rex and its prey were making deep low-frequency noises. Because Tyrannosaurus lacked a larynx like modern mammals such as lions and even likely lacked a syrinx such as those found in modern birds, it is unlikely that it was capable of roaring in a traditional sense as is often depicted in pop culture. Instead, it is believed that T. rex would have done low, deep rumblings and hisses, along with the occasional bellows and "roars" similar to living crocodiles.

A Tyrannosaurus relaxing in the sunrise by Fred Wierum.

From specimens such as Jane and B-Rex (MOR 1125), researchers were able to make a growth chart of Tyrannosaurus rex and found that once it hit its pubescent years, T. rex gained an average of 600 kg (1,300 lbs) a year until it hit adulthood at around 18 years of age. No eggs or hatchlings have been found of T. rex yet so what exactly it would have looked like at this stage of its life is not currently known. Because of this some scientists have suggested that this was because these animals rarely died during this age, though others have pointed out that this could simply be due to bias in the fossil record, which doesn't preserve small animals as well as larger ones. The oldest confirmed age for any Tyrannosaurus is currently 28 and belongs to Sue. At this age Sue was already showing signs of age due to arthritis and suggests that even though it didn't die due to old age it still was getting close to the end of its lifespan. It's unlikely T. rex lived much older than 30 years of age, suggesting they lived fast, hard lives.

For some time it was unknown just what Tyrannosaurus' integument consisted of. The classic depiction is that of lizard-like scales entirely covering its body, just like all dinosaurs were thought to have been like at the time. However, as time went on and more fossils were found that depicted dinosaurs with feathers, the question started to arise as to whether all dinosaurs would have had feathers in some way, including Tyrannosaurus rex. This seemed to become more possible when a decently-sized relative of T. rex, Yutyrannus, was found to in fact have been covered in feathers. This lead to the influx of paleo artists challenging the past depictions of the tyrant lizard by covering it from head to toe in downy feathers.

However, a study in 2017 showed that skin impressions of several derived tyrannosaurs, including T. rex itself, depict not the downy feathers that many experts had been expecting, but in fact small, reticulated scales. Although the skin impressions have only been in scattered patches among several species, the researchers concluded that there are enough scale impressions among so many different parts of the individual bodies that it's more likely that scales covered the entire animal instead of feathers only covering places that happened to not be preserved. This was further explained to be the case due to the animal's large body, which at its size any extra integument would have been a detriment rather than a benefit, especially since it lived in such a warm environment. There was a hypothesis for a while that perhaps the young tyrannosaurs would have had feathers when they were hatched and gradually lost them as they aged and grew in size. However, several researchers have pointed out that no animal today completely changes integument as it ages. Even birds today such as turkeys and vultures don't gain scales when they grow out of their facial feathers, it's just bare skin, so that hypothesis has been abandoned. If T. rex did have any feathers in life it would have been light downy feathers along its back similar to elephant hair.

A featherless Tyrannosaurus reconstruction by RJ Palmer.

Many patches along Tyrannosaurus' skull show extended patches of grooved, rugose bone, indicating that thick keratin would have covered much of the animal's face in life. These are most prevalent along the top of the snout, the crest ridges above the eye, and on the cheek of the upper jaw. It is believed this would have served as extra protection against rivals since bite marks show that these animals would have regularly bitten each other in the face during confrontation. Like all other theropods, Tyrannosaurus walked on two legs (known as "bipedalism") that were very well muscled and were made to support and balance the animal as it stood, walked or ran. Unlike the classic upright depictions of when it was first found, paleontologists now know that T. rex and most other theropods would have had vertical bodies in a neutral pose and used its tail and head to balance each other.

Tyrannosaurus rex had long been believed to be a hyper carnivore, the apex predator of Hell Creek. It certainly seemed to have the size and teeth to fill that role. However, all of this came to contention when in the 1990s, renown paleontologist Jack Horner proposed that T. rex was a lumbering scavenger that scoured the land for carcasses or bullied smaller predators away from their kills instead of hunting for themselves as had been the traditional view. He based these claims on observations to the animal's anatomy such as the tiny arms which he claimed would have been too useless in taking down large animals, its massive size which would keep it from chasing down potential prey, the fact its sense of smell was so strong which is only comparable to vultures which are known scavengers, its bone-crushing bite which carnivores that are typically depicted as scavengers like hyenas are known to have, and that its eyes would have been too small to properly hunt. Horner also noted that a specimen of Triceratops showed many bite marks on its pelvis and suggested that since it clearly took its time picking apart the carcass, the T. rex must have scavenged it.

This hypothesis was met with near immediate backlash. Rebuttals to Horner's claims were met by fellow paleontological and tyrannosaur experts such as Philip J. Currie, Thomas Holtz, Thomas Carr, and Robert T. Bakker, who noted that Horner misinterpreted several things about T. rex and the analogs he used. Tyrannosaurus did have small forearms, but they wouldn't have been necessary in killing its prey since it had a massive jaw that was more than capable of taking down large game, and even noted that not all predators kill with help from their arms, such as crocodiles and raptorial birds. It was a very massive animal, but it would still have been able to move fast enough to keep up with its rather slow-moving prey items such as Triceratops.

This was perhaps due to its unique arctometatarsus arrangement, which is the condition found in tyrannosaurs where the upper part of the middle ankle bone was pinched between the other two and would have allowed for greater agility and speed. The most recent estimates have found that T. rex could have moved anywhere from 20 km/h (12 mph) to 34 km/h (21 mph). It was also noted that elephants, which are of similar size to T. rex, are more than capable of being surprisingly fast when they want to be. However, due to its massive size alone, biomechanics researchers have noted that Tyrannosaurus would not have been capable of running.[1] Recent research has officially conducted the situation where the Tyrannosaurus is neither a fast nor an agile theropod.

New simulations based on tail movement showed that T. rex wasn't even a speedy walker! In a matter of fact, its preferred or most resonable walking speed clocked in at under 3 mph (5 km/h), about half the speed of earlier estimates. To put that into perspective, that's about the average walking speed for an average human, according to the British Heart Foundation.[2][3][4][5][6]

T. rex's sense of smell was astounding but that in no way indicated that it was a scavenger in nature since many modern day predators such as wolves and bears have great senses of smell as well. The massive bite compared to hyenas is also misunderstood since hyenas actually hunt their food far more often than they scavenge. As for its eyes, when scans of T. rex's skull revealed its braincase, it was found that a decent amount of it was dedicated to eyesight. Couple that with great binocular vision, and it would have allowed T. rex to locate prey at a great distance and been very useful for hunting prey. Not only that, but it was completely impractical that the only large carnivore in the area wouldn't have been hunting the massive herbivores in the ecosystem and keep a healthy population in the area. Horner's colleagues have pointed out that the next biggest carnivores in Hell Creek would not have been capable of taking down the multi-tonne prey on their own. There was also a fossil of Edmontosaurus found with a healed bite taken out of one of the tail vertebrae, indicating that it had escaped the attack and survived long enough for the wound to heal, and the only animal that was capable of making a bite like that was Tyrannosaurus rex.

An artistic rendering of a drowned group of tyrannosaurs and a crocodilian scavenging in the background. Illustration by: VICTOR LESHYK

Some paleontologists have suggested that perhaps Tyrannosaurus lived in familial groups where a pair of adults would raise a bunch of juveniles until they were old enough to leave and make families of their own. The main catalyst for this theory is from a close relative of T. rex, Albertosaurus has been found in large groups of varying aged individuals together. It's believed if this was the case, the smaller, faster juveniles would have acted as the pursuers who would drive weaker individuals away from their herds and chased them into the slower but stronger adults, who would end the job with a quick, powerful bite to a vital area. Whereas. more recent publication might have supports this group behavior for Tyrannosaurus, the publication studies a group of tyrannosaur fossils were found buried together at the “Rainbows and Unicorns Quarry” in Grand Staircase-Escalante National Monument. A skull of the same tyrannosaur species, depicted here, was found about two miles north of the group site. Titus even thinks that the site could be evidence that tyrannosaurs worked together as cooperative pack hunters. “Now you’ve got these giant terrestrial predators behaving in a group, much more akin to a pack of wolves and a pride of lions, [which] is staggering,” he says; but as he and other experts note, true pack hunting is rare among living predators. And social behavior among predators ranges from the barest tolerance of another individual to coordinated pack attacks. The new fossils are not the first example of tyrannosaurs discovered in the same place, but a meticulous reconstruction of the area’s geologic history provides strong evidence that they died in a group. The more elusive question is what they were doing together.

The 75-million-year-old site—named Rainbows and Unicorns Quarry by Titus’s colleague for its apparently incredible specimens—is the first of its kind in the southern U.S. However, it’s far from the only to hint that tyrannosaurs gathered in groups. One bonebed in Alberta, Canada, contains the bodies of 12 to 14 Albertosaurus that were seemingly concentrated together during a flooding event. In Montana, an area about half the size of a tennis court contains the remains of at least three Daspletosaurus. Even the site in South Dakota that yielded the famous T. rex fossil Sue contained remains of other T. rex individuals. Fossil tracks also add to the picture. In 2014, scientists announced that rocks in British Columbia preserve footprints of three tyrannosaurs that walked in the same direction within a short time of each other, if not at the same time. Researchers argued that the site could point to social behavior, even suggesting a collective noun for a tyrannosaur group: a “terror.” Thomas Carr, a paleontologist at Carthage College in Kenosha, Wisconsin, who wasn’t involved with the new study, says that finding more signs of social dinosaurs shouldn’t necessarily come as a surprise. Extinct dinosaurs belong to a bigger group called the archosaurs, which includes social animals such as modern birds, alligators, and crocodiles.[7][8][9] In the mid 2000s, a hypothesis arose that suggested since Tyrannosaurus had serrated teeth like today's Komodo Dragon, it would have had a septic bite that would infect victims that had initially escape its jaws due to the bacteria that would fester in its mouth due to the small pieces of rotting meat that would get caught between the serrations. However, this theory fell through for a few reasons. As it turned out, Komodo dragons don't have a deadly bite due to bacteria in its mouth but instead used venom to make its target bleed to death overtime if it escaped, so that analogy couldn't be used for T. rex. It was also found that serrations are in fact not capable of holding small pieces of meat in them, and if this was the case it was more likely the host itself would get its mouth infected by being constantly in contact with the bacteria. And finally, there would be no need for Tyrannosaurus to have evolved such large and powerful jaws if it was constantly relying on using a septic bite to take down its prey.

Sexual dimorphism is notoriously hard to distinguish in the fossil record. For a while, it was believed that female tyrannosaurs were the larger ones between the males, though recent analyses suggest there's no known reliable correlations to make this assumption. There is only one confirmed specimen of Tyrannosaurus to show sexual dimorphism, known as "B-Rex", and it was only found by breaking its femur and finding traces of soft tissue that resembles medullary bone like those found in modern-day birds when they're ovulating in order to provide extra calcium for the eggs.

In 2021, a paper by Charles Marshall et al. set to find the survival rates of Tyrannosaurus infants reaching adulthood, a process which had him attempt to find the approximate number of individuals who could have existed on earth. At the end of the study, it was revealed 2.5 billion individual adult Tyrannosaurus may have existed in total, meaning the species was one of the last "evolutionary supernovas" before the K-PG impactor. Tyrannosaurus assumed the role of a morphospecies, meaning the animal took many different niches until adulthood, where it reached apex predator. They compared Tyrannosaurus to many extant predators like lions and komodo dragons, comparing blood temperature, range, population density and growth curves to determine a likely number.

They found that among the 2.5 billion, only about 20,000 individuals could be supported at one time!

They estimate that for every one fossilized individual, 80,000 others did not preserve, and every 1 in 16,000 for the famous Hell Creek Formation. In the paper, they state the models are only a "ballpark estimate" and not data, but such information could be further revised in the future.[10][11][12]

Soichiro Kawabe et al. (2021) confirmed this. They found a complex network of sensory organs in the snout of Tyrannosaurus. Nerves are the most complexly distributed of all dinosaurs. They found it was able to recognize different areas, materials and movement with great accuracy. This would have enabled it to have eaten bodies depending on the situation. Neurovascular canals branched through the anterior of the dentary. Because it may have lacked the thick integument seen in crocodilians, it was likely more sensitive; and ornithischians, when compared, did not match the level seen in Tyrannosaurus. However, the team was not able to fully study the mandible and compare enough dinosaurs to be seen as sufficient, so their findings are seen as "a reasonable estimate"[13].

Paleoecology

Tyrannosaurus rex would have served the role as apex predator in its environment. In this case, the environment of Hell Creek during the Maastrichtian would have resembled northern Florida as a warm, moist delta ecosystem with tropical plants growing in swamps and floodplains. During this point in Earth's history the Western Interior Seaway was receding and where there was once ocean a few million years earlier there was now only river systems and a coastal plain.

Of all the known fauna in the area, Tyrannosaurus makes up around a quarter of all fossils found in Hell Creek, which is surprisingly high for an apex predator, though there could be bias in the fossil record with larger animals preserving better than smaller ones. Living alongside Tyrannosaurus in these fluvial habitats were the iconic three-horned Triceratops, which were the most plentiful animal in the area and would have been the main source of nutrition for Tyrannosaurus. The large hadrosaur Edmontosaurus would have migrated into Hell Creek fairly regularly and served as another favorite prey item for the local tyrannosaur. Other dinosaur residents would have included the armored club-tailed Ankylosaurus, the dome-headed Pachycephalosaurus, the ostrich-like Ornithomimus and the more nimble Thescelosaurus. Among T. rex's carnivorous dinosaur competition, there was the large dromeaosaur Dakotaraptor, the smaller dromaeosaur Acheroraptor, the large oviraptorosaur Anzu, and the troodontid Pectinodon.

Faunal distribution in the Hell Creek Formation.

While mammals were relatively rare in the area, Didelphodon was a relatively large one that lived alongside all of these dinosaurs. Because the environment was so tropical, Hell Creek would also have supported many animals that require a more warm environment such as crocodilians, turtles, and fish such as gar, sturgeon and even freshwater rays. Specimens of a freshwater mosasaur have also been described to have come from the same deposits as T. rex. Although it didn't live in Hell Creek itself, the gigantic sauropod Alamosaurus was contemporaneous with Tyrannosaurus and fossil evidence suggests that they would have even fed on these massive animals if given the opportunity, as bite marks and tyrannosaur teeth have been found with Alamosaurus bones. As top predator, it would have been T. rex's job to make sure the weak and sick individuals of these herbivores were taken out so the herd populations would be healthy and not overrun the entire ecosystem, so it would have acted as a keystone species.

There would have been many deciduous and coniferous trees and made dense forests in Hell Creek. These large plants would have made good places for hiding from prey to ambush (as Tyrannosaurus was suspected to do) or rest in the shade on a hot day. It is believed that instead of four distinct seasons like in modern-day western North America, there would only have been a dry season and a rainy season similar to the African Savannah. The average temperature for Hell Creek would have been much warmer and wetter than the average climate in the same region today. Because the environment was a fluvial one, most fossil remains found have been disarticulated. Tyrannosaurus and its cohorts were among the last non-avian dinosaurs, as Hell Creek goes all the way to the Cretaceous-Paleogene boundary where it is believed an asteroid the size of Mt. Everest crashed into the Yucatan Peninsula and set off a chain of events that would ultimately end in the mass extinction.

A Tyrannosaurus brain

Notable Specimens

The "Sue" specimen, stored in the Field Museum of Natural History, Chicago

Sue (FMNH PR2081):

Perhaps the most famous and most complete T. rex specimen, Sue is also among the largest, at 12.4 m (40 ft) long. It was found in the badlands of South Dakota in 1990 by Susan Hendrickson (who the animal was named after) and is over 90% complete. After years of legal disputes between the paleontologists who found the skeleton and the owner of the land it was found on, Sue sold for over $8 million to the Field Museum of Chicago and is now where it currently resides on display for the world to see. Along with being one of the largest and most complete T. rex specimens, Sue is also one of the oldest at 28 years of age. By now it was already showing signs of aging with arthritis being visible in the caudal (tail) vertebrae. Other pathologies found on Sue include healed rib fractures, healed infected broken leg bones, bites taken out of its vertebrae by other tyrannosaurs, and even a disease that caused unnatural holes to form in its jaw, which would have made eating incredibly painful and is believed to be the cause of its death. All of this indicates that even the most infamous predator in history would have struggled to survive.

Scotty (RSM P2523.8):

Scotty was discovered in Saskatchewan, Canada in 1991 by Robert Gebhardt. Phillip J. Currie and his team excavated the rest of the skeleton and started preparation in the Royal Saskatchewan Museum from there. Scotty was named after the bottle of scotch that was for celebration once the bones had been identified as belonging to T. rex. Once the matrix had been completely cleaned from the bones, analysis was able to be done on them and found that the skeleton was around 70% complete and likely belonged to a Tyrannosaurus that was bigger than any that had been seen before. Estimates put Scotty slightly outsizing Sue at 8.8 tonnes in weight, 13 m long and 4 m tall. Scotty is also significant for Canada because not only is it the biggest T. rex found from there, it's the biggest dinosaur found in the country period.

B-Rex (MOR 1125):

T-Rex skeleton in Carnegie Museum of Natural History

In 2000, experienced paleontologist Bob Harmon from Museum of the Rockies was digging in Charles M. Russell National Wildlife Refuge in Garfield County, Montana when he saw a bone sticking out of a steep cliffside. When it was found that the bones belonged to a Tyrannosaurus, it was nicknamed "Bob Rex" or "B-Rex" after the paleontologist who found her. Unfortunately, the fossil had to be split in order for it to be transported, however this allowed for some interesting discoveries to be made. Paleontologist Mary Schweitzer decided to take other opportunity of this situation and tried dissolving a piece of the fossilized bone in acid to see what would happen. As it turned out, when inspected under a microscope, Schweitzer found out that some of the fossils were elastic and resembled soft tissue such as blood vessels. This was the first sign of soft tissue in dinosaur fossils of any kind that had been found. Later on after further study, it was found that the soft tissue was actually medullary tissue, which is what is found in female birds that are about to lay eggs, indicating that B-Rex was female. This also was further indication of how closely T. rex, and by extension dinosaurs, were to birds. Interestingly, histology showed that B-Rex was only a subadult when she died, which suggested that T. rex didn't have to be skeletally mature to be sexually mature, and also that B-Rex was in the middle of laying eggs when she mysteriously died. Only about 37% of the skeleton was found (including nearly a complete skull), and what was found doesn't seem to indicate any injuries that would indicate how she passed away prematurely.

In popular culture

  • Tyrannosaurus is the most famous of all prehistoric animals, ever since its description in 1905, it's been extremely popular, and it's almost always the first dinosaur that comes to mind when the word "Prehistoric Animal" or "Dinosaur" is mentioned, being one of the only dinosaurs where nearly everyone actually fully knows its scientific name.

Tyrannosaurus as it appeared in Jurassic Park

  • It also starred in an episode of the re-known documentary series Walking With Dinosaurs where a female Tyrannosaurus tries her best to reproduce, but dies at the end along with her two children.
  • Tyrannosaurus rex appears in the Discovery channel show, Prehistoric: Denver where it battles Triceratops.
  • Tyrannosaurus rex appeared in the well-known documentary When Dinosaurs Roamed America, where a young teenaged Tyrannosaurus rex and it’s four siblings are taught by their parents on how to hunt.
  • Tyrannosaurus rex appears in the BBC series, Prehistoric Park where two youngsters that are brother and sister are named Terrence & Matilda.
  • Tyrannosaurus rex appears in the History Channel show, Jurassic Fight Club where in one episode a pair of Tyrannosaurus rex parents go on a hunt, leaving their two juveniles unattended, then a predatory Nanotyrannus attacks their children, killing one. but before it can finish off the other one, the mother T-rex comes back and ragefully kills the Nanotyrannus. In another, a Tyrannosaurus rex, attracted by the noise of a battle between a lone Edmontosaurus and a pack of Dromaeosaurus, takes the Edmontosaurus that was killed by the Dromaeosaurus, leaving them with just the tail.
  • Tyrannosaurus rex always appears in the show Dino Dan, Dino Dan: Trek’s Adventures & Dino Dana.
  • It also appeared in several other documentaries like Animal Armageddon, Dinosaurs Decoded, Truth About Killer Dinosaurs, T. rex: New Science, New Beast, Dino Gangs, Ultimate Guide: Tyrannosaurus rex, Clash of the Dinosaurs, and Last Day of the Dinosaurs.
  • Another documentary it's been in is Dinosaur Revolution, where it showed how a family of tyrannosaurs named Stumpy, Tinkerbelle & Junior lived until the K-Pg Extinction.
  • Tyrannosaurus rex appearances in 2 episodes of the 4 part PBS documentary program The Dinosaurs! "Flesh on the Bones" & "The Death of the Dinosaurs".
  • It also appeared on 2 episodes of the Six part PBS NATURE Program Triumph of Life It was seen in the 1st episode & was seen as a Skeleton ghost next to a pride of Lions in the last episode.
  • It was the first creature to be featured in Jeff Corwin's Giant Monsters, where it briefly chased Jeff who in turn explained how it may have hunted or scavenged (possibly both) by studying turkey vultures.
  • A Tyrannosaurus named Heart serves as the main protagonist of the 2010 anime film You Are Umasou.
  • It served as antagonists in the books and TV show of Dinotopia.

    Dinosaur Island Tyrannosaurus

  • It's also featured in many games involving dinosaurs, including all Jurassic Park Games, all Dino Crisis Games, and also Primal Carnage. It has also been featured in the Fossil Fighters series, appearing on the cover of the sequel, Fossil Fighters Champions. Tyrannosaurus appears in Turok, as there is a T. rex that has grown to intense size, as it is nicknamed "Mama Scarface", for the scar on its right eye. It also appeared in Jurassic The Hunted Where It was encountered twice in the campaign, once in its respective mission "Tyrant Lizard King" and once more in "Enter: Spike", where it falls victim to the game's Spinosaurus antagonist.
  • A giant robotic Tyrannosaurus is piloted by the red ranger in both the Mighty Morphin' Power Ranger series and the Dino Thunder series.
  • Tyrannosaurus is also the antagonist of nearly every episode of The Land Before Time.
  • It also starred in a Hollywood parody called T. rex: A Dinosaur in Hollywood, where they talk about how T. rex gained its fame throughout its discovery to modern-day movies.
  • It starred in the Disney movie Fantasia where it fought a Stegosaurus to the orchestra of "The Rite of Spring".
  • Tyrannosaurus rex was mentioned in the documentary series River Monsters on fish files.
  • It was also a main source for evolution in many episodes of the History Channel show Evolve.
  • It also served as the main dinosaur in a documentary called Tyrannosaurus Sex, where they talked about how T. rex and other dinosaurs may have reproduced.

Tyrannosaurus from Walking with Dinosaurs

  • Tyrannosaurus was also an antagonist in the comedy show Land of the Lost, a Hannah-Barbera show Dink, the Little Dinosaur named Tyrannor and the Korean film Speckles: the Tarbosaurus, where it was named "One Eye" and killed the family of the main character "Speckles", a Tarbosaurus.
  • Jack Horner also talked about T. rex and why he believes it's mostly a scavenger in Valley of the T. rex, despite the theory already being disproven by then.
  • Tyrannosaurus also appeared in five episodes of Planet Dinosaur, but it was only was shown in a database.
  • T. rex is one of the main dinosaurs in the Dinosaur themed restaurant T-Rex Cafe located in Disney World and Kansas City. It's mascot is also a T. rex named Dexter.
  • A T-rex nicknamed "Grumpy" by the characters appeared in the 2009 film Land of the Lost.
  • Tyrannosaurus rex is seen as The Disneyland train travels to the Primeval World diorama. In it, he is seen reenacting his battle from Fantasia.

Tyrannosaurus as it appeared in Jurassic World

  • In Walt Disney World's Epcot there was a ride known as Ellen's Energy Adventure where several dinosaurs could be seen that are similar to the ones during Fantasia's The Rite of Spring. Most notably, there was a large Tyrannosaurus attacking a Stegosaurus over a cliff.
  • At Disney's Animal Kingdom DINOLAND USA There's a Life Sized Statue of T. rex seen in Cretaceous Trail And at the entrance to the Ride DINOSAUR another T. rex statue was seen only a head & neck. At Downtown Disney's T-Rex Cafe, there is a large Tyrannosaurus with his young.

Momzilla in Ice Age 3

  • A Family of Tyrannosaurus (Momma Dino & her babies Egbert, Shelly and Yoko) appeared in the 2009 Blue sky studios film Ice Age: Dawn of the Dinosaurs as the Protagonists & Support Characters.
  • Three Tyrannosaurus (Butch, Nash and Ramsey) appeared in the Disney/Pixar film The Good Dinosaur.
  • Tyrannosaurus made some appearances in DinoRiders.
  • A Tyrannosaurus rex and leader of the Tyrannos named Gangus Rex appears in Various episodes of Dinosaucers, Gangus Rex Devolve into his ancestral appearance in only a couple episodes.
  • Tyrannosaurus made some appearances in Cadillacs & Dinosaurs. "Both Some Comic Books & a few episodes nicknamed a Shivet".
  • Tyrannosaurus and most others of it's kind appeared in several episodess of Kong: The Animated Series. A couple made a cameo appearance in the movie Kong King of Atlantis & only One was seen on the other Film Kong Return to the Jungle.
  • The Tyrannosaurus appears in Dino Hunter: Deadly Shores in Region 1. It also has a Trophy Hunt variant named "Tyrannos", which appears to be a young, but wreckless Tyrannosaur.
  • A Female Tyrannosaurus (Tyra) appeared in a Film called DINO TIME AKA BACK TO THE JURASSIC.

Grimlock with his crew

  • Grimlock of the Transformers variety turns into a T. rex.
  • A male Tyrannosaurus rex appears in the science fiction actionadventure horror comedy film Raptor Ranch (known as The Dinosaur Experiment) where it fights a mated pair of Megalosaurus.
  • An Tyrannosaurus appears in the video game named Parasite Eve as an boss, in one of the cutscenes it is shown that the t-rex is reanimated by Eve's Neo mitochondrial powers.
  • Tyrannosaurus Rex also appears in the mobile game Jurassic World Alive as an Epic dinosaur, and is a vital ingredient for the Indominus Rex.
  • Tyrannosaurus Rex made an appearance in the ROBLOX game called "Dinosaur Simulator". Defaulted to you as a free dinosaur.

Mario being chased by a Tyrannosaurus Rex

  • Tyrannosaurus Rex appeared in a Nintendo Switch game named "Super Mario Odyssey".
  • Tyrannosaurus appeared in the 2018 Roblox game Dinosaur World Mobile as a gamepass creature.
  • Tyrannosaurus Rex appeared in Granblue Fantasy as Unite and Fight January 2021 raid boss.
  • Tyrannosaurus Rex appeared in the 2000 mockbuster film Dinosaur Adventure('Yee movie)
  • It will appear in the upcoming video game Saurian as a playable dinosaur.

Other Wikis

Prehistoric wiki

References

Documentaries & other Media

  • T. rex: New Science, New Beast
  • Dino Gangs
  • Ultimate Guide: Tyrannosaurus rex
  • The Last Days Of The Dinosaurs
  • T. rex: Back to the Cretaceous
  • T. rex: A Dinosaur in Hollywood
  • Evolve
  • T. rex: Warrior or Wimp?

Tyrannosaurus Chicks

  • Dinosaur 13

Books

  • The Complete Guide To Prehistoric life; by Tim Haines and Paul Chambers
  • Ultimate Book of Dinosaurs; by Paul Dowswell, John Malam, Paul Mason, Steve Parker
  • Dino Wars; by Jinny Johnson, consulted by Michael J. Benton
  • Vertebrate Paleontology; by Michael J. Benton
  • How do We Know Dinosaurs Existed; by Mike Benton
  • The Audubon Society Pocket Guides Familiar Dinosaurs; by Alfred A. Knopf
  • Uncover T. rex; by Dennis Schaz
  • The Dinosaur Heresies; by Robert T. Bakker
  • Life-Sized Dinosaurs; David Bergen
  • Rise and Fall of the Dinosaur; Joseph Wallace
  • Tyrannosaurus Sue; Steve Fi

Patchwork T-rex

From Muppet Babies-1984

From Dino Digs-Alpha and Omega



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