Tyrannosaurus (Tyrant Lizard) is a genus of tyrannosaurid theropod dinosaur that served as the apex predator of western North America during the Maastrichtian stage of the Late Cretaceous Period. It is arguably the most well-known dinosaur to have ever walked the Earth.
The species depicted on Prehistoric Planet is the widely-recognized Tyrannosaurus rex (named after the Latin term for "king"), which lived 68 - 66 million years ago, during the latter half of the Maastrichtian stage. A specimen discovered in 1983 in the Hall Lake Formation of the McRae Group in New Mexico, USA was eventually proposed in 2024 to be a distinct species named Tyrannosaurus mcraeensis, which lived 73 - 71 million years ago, from the end of the Campanian stage to the early Maastrichtian stage (though it should be noted that the age of this second species is based on the rock beneath it and not on the fossil itself).[1][2]
Tyrannosaurus rex is the last, largest, and most heavily-built of the tyrannosaurs, a group of massive predators that dominated their respective ecosystems during the Late Cretaceous Period. Previous calculations regarding the size of Tyrannosaurus rex estimated lengths of up to 14 meters (46 feet), but these measurements are now considered outdated overestimates in the light of more recent studies, which estimate an average of 3.66 - 4 meters (12 - 13 feet) in height,[3][4] 12.3 - 12.4 meters (40 - 41 feet) in length,[5][TH 1] and 7 - 8 metric tons (7.7 - 8.8 short tons) in weight.[5][8] The largest known Tyrannosaurus is specimen RSM P2523.8 (nicknamed "Scotty" after the celebratory bottle of scotch shared by the team that discovered the specimen), which achieved a length of 13 meters (43 feet) and a mass of almost 9 metric tons (10 short tons),[6][7] though it should be noted that "Scotty" is an exceptionally-large individual, and most T. rexes likely did not grow that big. While evidence suggests that "Scotty" is actually one of the youngest and least mature of the adult T. rexes found so far (having been approximately 23 - 27 years old when it died), thus implying a greater potential maximum growth size for the species,[26] this does not explain how older T. rex specimens, like 28 year-old FMNH PR 2081 (nicknamed "Sue" after American explorer and fossil collector Sue Hendrickson, who discovered the specimen in South Dakota on August 12, 1990), were smaller than it. This suggests that "Scotty" gained its exceptional size not due to age, but due to genetic factors, an abundance in resources, ideal environmental conditions, or a combination of these various factors. In 2022, a paper by Gregory S. Paul brings up the theory that there may be three Tyrannosaurus species (T. rex, T. regina, and T. imperator) instead of just one based on size and morphological differences between various specimens (the idea being that the robustness of some specimens cannot simply be attributed to individual variation). This theory has not seen widespread support, with other paleontologists like Dr. Thomas D. Carr and Dr. Lindsay Zanno considering the work unconvincing and lacking in validity.[27][28][29]
It has been suggested that other T. rex individuals may be larger than "Scotty". Specimen BHI 6248 (nicknamed "E.D. Cope", named after renowned American paleontologist Edward Drinker Cope), discovered in June 2000, possesses a femur circumference of 63 centimeters (2 feet, 1 inch), which exceeds even those of "Scotty" (59 centimeters, or 23.23 inches), though it is only 10% complete, and its femur is only 127 centimeters (4 feet, 2 inches) long; for comparison, an average T. rex femur is 130 centimeters (4 feet, 3 inches) long with a circumference of 55 centimeters (1 foot, 10 inches), while the femur of "Sue" is 132.1 centimeters (4 feet, 4 inches) long with a circumference of 58 centimeters (1 foot, 11 inches).[27][30] Another T. rex said to be possibly bigger than "Scotty", a specimen nicknamed "Bertha", was unearthed in North Dakota in the 1990s, and is only known from three bones (a tibia, a fibula, and a femur with a girth that is said to exceed that of "Sue"), making it too short and incomplete to readjust the acceptable upper size limits of Tyrannosaurus until further studies and support are provided.[31][32][33] A third individual named "Goliath" was discovered in September 2024, and is said to have a femur length of 137.1 centimeters (4 feet, 6 inches) and a circumference of 64.77 centimeters (2 feet, 1.5 inches), slightly surpassing the length of the femur of "Scotty" and the circumference of the femur of "E.D. Cope". However, it is not as large as it is claimed to be, as it is only around 3.7% longer and taller than "Sue".[30][TH 2]
As the largest predator to ever walk in North America, T. rex can easily process large sources of food like Alamosaurus corpses, and scare off smaller carnivores like troodontids
In 2024, a study suggested that T. rex may be 70% larger than existing fossils indicate. Based on the modeling of its growth curve, T. rex can reach an absolute maximum length exceeding 15 meters (50 feet) and weigh approximately 15 metric tons (16.5 short tons). If the species displayed sexual dimorphism similar to the American alligator, T. rex can go up to 24 metric tons (26.5 short tons), but since sexual dimorphism is considered very unlikely (otherwise, significantly larger specimens would have already been found), this estimate is not given any further serious consideration. Scotty is already considered to be in the Top 1% of the largest T. rexes that ever lived, so should a T. rex 70% larger than it actually be discovered, it would be in the Top 0.01%, and therefore even less of a representative of the average T. rex size. The paper cautions against taking these calculations at face value, however, as these estimates are merely based on hypothetical modeling as opposed to actual hard fossil evidence, and should therefore be treated as a null hypothesis in the absence of size-limiting constraints. Furthermore, the paper simply uses T. rex as an example, for the idea that paleontologists have likely not found the biggest specimen of the species can apply to not only all dinosaurs (not counting living birds), but also to many other extinct animals.[34][35][36]
Size comparison of several carnivorous theropods (T. rex in blue)
“ Deinocheirus. It's even taller than T. rex, and its massive duck-billed snout is very effective in gathering water plants. ”
Oftentimes, T. rex is used as a standard by which other theropods are measured. Prehistoric Planet itself does this, with Deinocheirus (possessing a height of 4.4 meters, or 14 feet)[37] being introduced in the Freshwater episode as "even taller than T. rex". While not the longest or tallest theropod, in terms of body mass, Tyrannosaurus rex is the heaviest known theropod, and is thus seen as the most powerful, a view that stands more than a hundred years after its remains were first discovered.
Growth and Lifespan[]
Tyrannosaurus juveniles have a sleeker form compared to the adults
T. rexes have an S-shaped growth curve, starting life with slow growth, then experiencing a great, rapid shift in size and physique before growth slows down again. Juveniles start out with larger eyes, a more gracile snout, slender legs, proportionally longer (but still tiny) arms,[DN 2] and an overall slimmer profile. Even at this young age, however, T. rexes can reach around half of their adult size, as is the case for specimen BMRP 2002.4.1 (nicknamed "Jane", previously regarded as a separate species called Nanotyrannus, though as of 2024, this theory has been subjected to debate once more),[38][39][TH 3] which measures 6.5 meters (21 feet) in length and approximately 639 - 1,269 kilograms (1,409 - 2,798 pound) in weight by the time it died at 11 years of age.[5] Young T. rexes would remain under 1.8 metric tons (2 short tons) in weight until they are around 14 years old, by which point they grow at a dramatic rate, gaining an average of 600 kilograms (1,323 pounds) a year for the next four years. After this, growth slows down once more, as is the case for "Sue",[4] which, despite being 28 years old, is only 600 kilograms (1,323 pounds) heavier than a 22 year-old Canadian T. rex specimen.[40][41]Tyrannosaurus is also capable of slowing down its growth. Since larger animals require more food and are more vulnerable to environmental changes, the theropod's strategy of keeping its size low is a good means of adapting to times when resources are less abundant and conditions are harsher, with these studies also confirming that Nanotyrannus is simply a juvenile Tyrannosaurus following an analysis of the bone growth rings of both animals.[42] Conversely, this control of growth could also help explain how "Scotty" grew to be the largest T. rex ever discovered so far despite being one of the youngest, indicating that the specimen may have lived during a time when resources were plenty and conditions were ideal.
Of the 15 chicks of a T. rex father, only four are left, with one recently eaten by a mosasaur
“ Tyrannosaurus rex often lose at least two-thirds of their original brood of 15 or so in the first year. Now, there are only four. ”
Once a T. rex reaches maturity at around 18 - 19 years of age, their growth slows down once more.[40] The oldest T. rex specimen known so far is RGM 792.000 (nicknamed "Trix" after former Queen Beatrix of the Netherlands), which lived to be 30 years old,[23][24] two years more than "Sue", as determined by their bone growth rings.[3][4] It has been argued that most T. rexes do not get to live as long as either of these two specimens, for they usually die around six years after reaching maturity.[22] In a 2013 lecture, Dr. Thomas Holtz attributes this to the fact that T. rex was an r-strategist, an animal that reproduces quickly, spawns many babies at a time, does not provide extensive parental care, and essentially "lived fast and died young".[TH 4] This is reflected in the first segment of Coasts, where the T. rex only provides loose parenthood to his hatchlings, taking them to an island where they can grow up safely, while at the same time not guarding them too closely, even forcing them to find their own food.
Wounds inflicted by a recently-slain Triceratops on an old male T. rex, serving as a reminder of the fatal dangers he can face, and a testament of his experience as a great survivor
“ Decades of battling armored prey has scarred his body. One battle even cost him the tip of his tail. These new injuries are more serious. At his great age, infection is a real risk. River water could help to clean his wounds. He stands a good chance of living to fight another day... but that day could come sooner than expected. ”
Gregory S. Paul also agrees that T. rexes reproduced quickly and died young, but instead attributes this short lifespan to the dangerous lives these predators led,[43] with various fossils showing signs of vicious facial biting, bones broken and healed several times over, and even parasitic infections like an ancient form of Trichomonas gallinae. The second segment of Freshwater showcases the several injuries a tyrannosaur may suffer, with an old male bearing damage gained in prior battles (one of which cost him the tip of his tail), with the most recent one being a considerable slash on his side inflicted by a Triceratops he has recently brought down. While these can indeed prove risky (and may even cost him his life one day), these scars also serve as evidence that he faced several dangerous challenges in life and survived, with these testaments of his strength, experience, and triumph proving attractive to any onlooking female.
Conversely, more up-to-date studies in 2020 suggest that T. rex reached skeletal maturity at around 16 - 22 years of age, and, based on histological evidence, could live up to 33 years,[25] though it is not considered unreasonable to hypothesize that some T. rexes lived longer than what current findings suggest.[44]
As a predatory animal, Tyrannosaurus would have needed to be intelligent enough to properly plan out its approach to various situations, for not all scenarios in nature and life can simply be solved by brute force alone. A study in 2023 by Dr. Suzana Herculano-Houzel even suggested that, given the cerebra of modern squamates, birds, and turtles, large theropods like Allosaurus and T. rex had as many neurons as baboons, and therefore may have been capable of tool use and even establishing a sort of "culture", practices that persist through generations, like birds and primates do today.[45] However, a 2024 study by several people, among them Dr. Thomas Carr, Dr. Thomas Holtz, and Dr. Darren Naish (who has, for years, challenged and corrected old, outdated views about reptiles being dumb, even depicting T. rex as being capable of planning complex hunting tactics on Prehistoric Planet, a show he served as a lead consultant of), rebutted this view. One reason given in opposition of T. rex's baboon-like mind is that dinosaur brains are not exactly like the brains of extant reptiles and birds, so their neuron count would be lower than initially proposed. Furthermore, their study concluded that various factors that support intelligence, like efficient metabolism and life history, should not be taken as suitable proof of high, primate-like cognitive abilities, as the complex subject of dinosaur intelligence cannot be properly or definitively answered by just these factors.[44] Even if T. rex really did hold a great number of neurons, absolute brain size and a high neuron count does not immediately make the animal very intelligent, as proven by giraffes, which also have a high amount of cerebral neurons. The intelligence of T. rex was likely closer to that of monitor lizards and crocodiles (which are intelligent in their own right) rather than that of primates.[46]
T. rex flips over a dead turtle, pragmatically choosing to scavenge rather than unnecessarily expend effort in hunting live prey at all times
The series demonstrates T. rex's intelligence in every segment it appeared in. The first segment of Coasts shows a T. rex risking his life and those of his offspring in order to reach an offshore island, having recognized the benefits of the area, which provides not only food that requires little to no effort to eat (a dead turtle), but also a safe place to raise his hatchlings, a sanctuary where they can freely practice the instincts they need for adulthood. In the second segment of Freshwater, the male and female T. rexes, while cautious, did not immediately resort to violence. Both eventually viewed their chance encounter as an opportunity to mate, with the female recognizing the male's power and experience (as indicated by his many scars) as proof that he is a suitable father that will bring forth excellent brood. In the fifth segment of Swamps, the two subadult T. rex brothers recognized their strength as a duo, and, through stealth and confusion, successfully singled out an Edmontosaurus, forcing and trapping their target in a deadly nocturnal ambush. Finally, in the first segment of North America, T. rex once again found the opportunity to feed without need to exert effort by scavenging a dead Alamosaurus, but backed off when a pair of Quetzalcoatlus harassed him. Although an adult T. rex is more than capable of overpowering and killing the azhdarchids, the theropod recognized that battling them is not worth the risk of losing an eye, a valuable hunting asset, so he instead chose to leave and return at a later time when the pterosaurs have had their fill, for the huge body of a titanosaur clearly holds enough meat to last several carnivores in the area for many days or even weeks.
“ The fields of vision of its two eyes overlap substantially, giving it very good depth perception, which would have made it a very effective predator. ”
― Professor Paul Barrett, Natural History Museum
Tyrannosaurus rex has forward-facing eyes (topped with intimidating, prominent crests) that are 14 centimeters (5.5 inches) in diameter, the largest of any dinosaur (and perhaps of any land animal), giving it a binocular field of view of around 55 degrees when it tilts its head 10 degrees downward, same as the conservative estimates for the binocular field of view of Velociraptor, giving it excellent binocular vision wider than those of modern hawks, with visual acuity that is possibly 13 times greater than that of a human's eye (by comparison, an eagle's eye has 3.6 times the visual acuity of a human's eye), though limited by other factors like limiting far point (assuming that such factors were proportional to that of a falcon, a T. rex may have had a limiting far point of 6 kilometers or 3.73 miles, better than that of a human). The large size of its eyes also gives it remarkable scotopic (low-light) vision, making it a fearsome predator in any environment, and at any time of the day.[10][DN 1] However, in 2021, a comparison with the alvarezsaur Shuvuuia suggested that T. rex and Dromaeosaurus primarily hunted during daytime.[47][48] Even so, Prehistoric Planet depicts T. rex and other carnivorous theropods like Kuru kulla (a relative of Dromaeosaurus) as being able to hunt effectively during the night, as the idea is still considered a plausible one.
T. rex's pupil, dilated like an owl's, peering through the forest in the darkness of the night
“ Tyrannosaurs have the largest eyes of any dinosaur, which gives them superb, low-light vision. And they're able to move through the forest in near-silence thanks to cushioned pads on their feet. ”
It is possible that T. rex was neither fully diurnal nor nocturnal, but cathemeral, active at irregular intervals throughout the day, much like lions. This idea appears to have been depicted to an extent on Prehistoric Planet, with a T. rex shown waking up from a short nap sometime after killing a Triceratops in the second segment of Freshwater, and one T. rex waking up his brother to prepare for a night hunt in the fifth segment of Swamps.
The right eye of a T. rex, scratched up and no longer as clear as its left eye
“ Quetzalcoatlus, a giant pterosaur. One of the few creatures that will challenge an adult tyrannosaur. One strike from its six foot-long beak could easily cost T. rex an eye. ”
As a sight-reliant predator, the eyes of Tyrannosaurus are of utmost importance to it. Hence, when a fight is not worth the legitimate threat of losing sight completely (especially when it has lost sight in one eye due to prior experience), it would prioritize keeping its remaining means of sight intact.
Hearing and Vocalizations[]
T. rex used its remarkable sense of hearing with its powerful sense of sight to pinpoint distant prey quickly and accurately
“ Large optic and olfactory lobes suggest an excellent sense of sight and smell. But it doesn't end there. The inner ear is adapted to pick up low frequencies, an advantage when detecting prey over long distances. ”
T. rex has extensive tympanic pneumaticity and a long cochlea by theropod standards, indicating that the capability to detect low-frequency sounds over long distances was important to the theropod, not only for accurately honing in on prey from far away, but also for socialization, as this also implies that T. rex could communicate via low-frequency sounds that may not be audible to animals with less-sensitive ears, potentially allowing them to engage in seemingly silent, secret communication while hunting.[49][PhP 1]
A T. rex responding to a potential rival on the other side of a shallow river
“ Another T. rex. A stranger. But this newcomer has a different smell... ”
Tyrannosaurus rex and other large theropods are usually depicted in popular culture as roaring, with the (oftentimes modified and distorted) sound effects of various big cats and other large mammals like elephants being used. However, current scientific theories suggest that, due to their different throat anatomy, dinosaurs would not have roared or vocalized the same way mammals do. However, this does not mean that they outright lacked the ability to roar in their own way, as it is believed that they may have at least growled and bellowed like crocodiles, or let out bird-like vocalizations, some of which are done without even having to open their mouth since they only need to accumulate and move enough air to vibrate their throats or other internal structures.[DN 3][50][51]
A female T. rex (right) reciprocates the rumbling mating calls of an old, experienced male
“ It's a female. She's younger, and smaller. But nonetheless, she might also be a rival. He, however, makes it clear that he's not interested in fighting. He would prefer to mate. She seems to approve. ”
On Prehistoric Planet, T. rex, along with most of the other dinosaurs in the series (especially other theropods), communicated with crocodile-like growls and hisses as well as low drumming and booming sounds like an ostrich or emu, as shown in the second segment of Freshwater, where the old male T. rex and a younger female bellow and growl at each other at first, then greet each other with close-mouthed throaty rumbling when the situation has become less hostile.
The sounds of the juvenile tyrannosaurs were originally meant to be modified crocodile sounds, though when these seemed insufficiently one-dimensional and too obvious, Prehistoric Planet turned to various bird vocalizations. Among those used are the pitch-changed calls of a common starling, and the slowed down cries of a cactus wren.[PhP 2]
Jaws and Dentition[]
T. rex crunching through the plastron of a turtle with five tons of bite force
“ T. rex has the most powerful jaws in nature, and can bite with the force of over five tonnes. ”
With a 1.5-meter (5-foot) skull weighing around 272 kilograms (600 pounds),[9]Tyrannosaurus rex has one of the most powerful bites of any terrestrial predator, able to crush bone with strength sufficient to destroy a car.[52] Estimates in 2012 set its bite force to 35,000 newtons or 3.6 metric tons (4 short tons) at the front of its jaws, and 57,000 newtons or 5.8 metric tons (6.4 short tons) at the back,[53] but 2018 revisions to these calculations lowered the posterior bite force to 53,735 newtons or 5.5 metric tons (6.1 short tons).[11] Due to this, each individual tooth can exert as much as 3,000,000 newtons (305,915 kilograms) per square meter (435,113 pounds per square inch).[15] A 2022 study that brought up values calculated from dinosaur jaw adductor muscles also supports this idea, estimating that a T. rex with a skull width of 90 centimeters (3 feet) possesses an anterior (front) bite force of 25,418 newtons or 2.6 metric tons (2.9 short tons), and a posterior (back) bite force of 48,505 newtons or 4.9 metric tons (5.4 short tons),[12] while a study in 2023, using not just the adductor muscles but also other jaw muscles, gives an even higher estimate of 63,332 newtons or 6.5 metric tons (7.2 short tons) based on the remains of FMNH PR 2081 (the "Sue" specimen).[13] Overall, T. rex has one of the most powerful bites of any land animal that ever lived, only surpassed by large crocodilians, like the Miocene caiman Purussaurus, which has an estimated bite force of 69,039 newtons or 7.04 metric tons (7.8 short tons),[54] and the Campanian alligatoroid Deinosuchus, capable of exerting around 102,803 newtons or 10.5 metric tons (11.6 short tons) with its jaws.[55]
As indicated by a study in 2012, T. rex likely ate Triceratops starting from its nutrient-rich neck muscles
To help generate these forces, T. rex can open its jaw up to 80 degrees,[16] and it has a stiff skull, fixed and rigid to withstand the stress of its own bite.[52] Despite this power, certain prey animals with healed Tyrannosaurus bite marks on them (like Triceratops and Edmontosaurus)[56][57] indicate that, given the size and power of T. rex's prey, it is still possible for victims of a T. rex attack to escape, maybe even fight back, and survive. In the fifth segment of Swamps, an Edmontosaurus managed to survive several bites and even put up a decent struggle against its attacker before finally being brought down by the combined effort of two subadult T. rexes. Juvenile T. rexes have a bite force of around 5,641 newtons, or 576 kilograms (1,270 pounds),[58] slightly greater than that of a spotted hyena, which can bite at around 4,500 newtons, or 460 kilograms (1,014 pounds).[59]
T. rex tearing through the tough flesh of an Alamosaurus
“ Tyrannosaurus rex. North America's top predator. With his six inch-long teeth, tearing through an Alamosaur's tough skin is not a problem. ”
The teeth of T. rex, numbering around 50 - 60, measure around 30 centimeters (12 inches) long,[9] the largest known of any carnivorous dinosaur. It should be noted, however, that the lower half of the tooth is embedded in the animal's gums as the root, hence, Prehistoric Planet only brings up the length of the exposed part of the tooth, the crown.[14] Compared to most carnivorous dinosaurs, which have thin, blade-like teeth for tearing through flesh, T. rex teeth are robust and reinforced with ridges, allowing the teeth to withstand the stresses of both the animal's own bone-crushing bite and the struggles of captured prey. While studies regarding the matter are still debated, it is now believed that, unlike crocodiles, which have exposed teeth that are kept moist by their aquatic habitats, T. rex and other theropods kept their teeth concealed within lips, like lizards and other primarily-terrestrial animals, thus protecting their enamel from degradation.[60][61] As is the case for most reptiles, T. rex would have constantly lost and replaced all of its teeth, shedding and regrowing a few thousand in its lifetime.
T. rex, like most predators, does not possess special bacteria in its jaws; grievous infection is more likely to come from pathogens in the environment
It was once proposed that T. rex killed prey with very infectious saliva like a Komodo Dragon,[62] with the serrations in their teeth retaining pieces of previous meals to cultivate bacteria,[63] though the tooth serrations of tyrannosaurs are cube-shaped, not rounded like those of a Komodo Dragon.[64] Today, this theory is not supported, since Komodo Dragon saliva is no different from those of other carnivores.[65] Instead, they relied on a combination of shock, blood loss, venom (Komodo Dragons, like all monitor lizards, possess venom glands in their lower jaws, allowing them to inhibit blood clotting, lower blood pressure, paralyze muscles, and induce hypothermia),[66] and the harsh conditions of their habitat (Komodo Dragon victims get infected with sepsis not due to the presence of special, highly septic saliva, but due to the feces-filled waters and overall warm conditions of the environment which help promote bacterial growth).[65] Evidence of prey that survived and healed from a T. rex attack[56][57] make it highly unlikely that T. rex had a venomous bite, and, with its six-ton bite force being one of the most powerful of any land animal that ever lived, the evolution and usage of toxins is very much unnecessary. However, there still remained the threat of a T. rex bite getting infected, given the warm, wet environments where T. rex lived in, similar to the habitat of Komodo Dragons today.
Arms[]
The arms of T. rex, though small, are surprisingly strong, with there being proof that they were still used by the animal
Tyrannosaurus is also known for its notoriously-short arms, each almost a meter (3 feet, 4 inches) long and ending in two curved claws (these proportions are like those of a human with arms that are 13 centimeters or 5 inches long). However, these arms are deceptively strong due to extremely thick cortical bones and powerful muscles. The biceps alone are able to lift 200 kilograms (441 pounds),[18] making them 3.5 times stronger than the human equivalent, with other muscles like the brachialis further increasing the strength of elbow flexion. Conversely, a T. rex's shoulder joint only allows only up to 40 degrees of motion, while the elbow joint just permits up to 45 degrees, making its overall forearm motion range rather limited, especially compared to others like Allosaurus (shoulder joint is capable of 65 degrees of motion, while the elbow can go for 62 degrees), Deinonychus (shoulder and elbow joints allow up to 88 and 130 degrees of motion, respectively) and humans (360 degrees of rotation at the shoulder, can move through 165 degrees at the elbow). The short arm length, robust construction of the arm bones, tremendous strength of the muscles, and the limited range of motion of T. rex's forearms are all adaptations to withstand the impact and stress of coming into contact with struggling prey, which would explain why the arms show stress fractures, damages formed by regular usage and not isolated, one-off events. While the arms of many theropods grew long and mobile in order to prioritize reaching out to grab prey, T. rex's short and less mobile yet more robust arms are meant more for stabbing prey and clutching them, with its hooked claws pointing somewhat inward to prevent grabbed prey from slipping out of its grip. In essence, like its jaws, T. rex's arms traded range and flexibility for brute force and more secure prey retention. Overall, it further proves how, rather than being an obligate scavenger with vestigial arms, T. rex was an active predator that attacked live animals, stabbing and holding prey with its forelimbs while delivering one or several bone-crushing bites.[17]
Originally believed to be ectothermic ("cold-blooded", reliant on the temperature of their environment for their body heat) like most reptiles, dinosaurs are now believed to be endothermic homeotherms ("warm-blooded", capable of maintaining a constant body temperature regardless of factors outside the body). In the case of T. rex, its high growth rate serves as one indication of its high metabolism.[67] A more recent study in 2022 brings up the spectroscopic study of something that correlates with metabolic rates, lipoxidation signals (byproducts of oxidative phosphorylation, the process where cells use enzymes to oxidize nutrients and therefore produce chemicals to create adenosine triphosphate), as evidence of endothermic metabolism in T. rex, almost on par with those of modern birds. This same study suggests that large dinosaurs were not gigantothermic (reliant on their massive bodies to keep up their temperature, an adaptation usually seen in ectotherms), but true endotherms, with the implication that endothermy was an ancestral trait to ornithodirans (the clade that includes both dinosaurs and pterosaurs).[68]
Juvenile T. rexes may have had feathers, but, assuming it exists, they likely lost this heat-retaining coat gradually as they grow
Amongst theropods, insulation is usually attained and sustained with the help of size (gigantothermy), feathers, or both. Although feathers are known in basal tyrannosauroids like the 9-meter (30-foot) proceratosaurid Yutyrannus huali (the largest feathered animal known so far),[69][70]T. rex skin impressions lack direct evidence of feathers, indicating that T. rex and other advanced members of the tyrannosauroid superfamily were, for the most part, scaly.[71] However, based on the exhibit by paleontologist Mark Norell, the T. rex: The Ultimate Predator, recent and more accurate studies helped the reconstruction of a juvenile T. rex model. Hatchlings may have been covered in feathers, which prompted the scientists involved to propose that, while T. rex was primarily covered in scales, it also had a mullet of feathers on its head, neck, and tail.[72][73] With these findings, Prehistoric Planet chose to portray T. rex with a coat of feathers when young, the animal gradually losing its plumage as it grows, until all that is left on the adults are some faint, almost hair-like remnants. This is likely because their large bodies and bodily functions are able to keep them sufficiently warm without the need for a feathery coat.
Speed[]
A T. rex and his five chicks swimming away from a hungry mosasaur
As a theropod, T. rex also boasts remarkably muscular, powerful legs, with three large, clawed toes along with a smaller fourth digit that did not touch the ground, indicating its vestigial nature. These legs would have served multiple purposes, including kicking and stomping on prey, walking, running, and potentially even swimming, as depicted on Prehistoric Planet. While its speed is not explicitly stated on the show, it is believed that, despite being incredibly robust, with a body made stocky by layers of muscle and fat, T. rex is capable of running at decent speeds ranging from 4.5 - 6.8 meters (15 - 22 feet) per second, or 16 – 24 kilometers (10 - 15 miles) per hour to 20 meters (66 feet) per second, or 72 kilometers (45 miles) per hour, though these have been considered infeasible even as far back as 2002.[74]
More recent, up-to-date studies have cast further doubt on these high-speed capabilities. A 2017 study brings up how, due to Newton's laws of motion, mass must overcome inertia, thus, a larger animal, despite having more muscles to power their limbs, would not always be faster than smaller animals with lesser muscles, as proven by the cheetah, which is faster than beetles, mice, rabbits, and elephants. In the study, a mathematical model based on an animal's weight and the medium it moves in (land, water, or air) is used on T. rex, Triceratops, Brachiosaurus, and others, with the results of the complex simulation indicating that T. rex could only run up to 27 kilometers (17 miles) per hour, and it would likely exhaust itself before reaching its top speed due to anaerobic metabolism.[21] Furthermore, another 2017 study, focused on the skeletal loads of large theropods, brings up how speeds over 18 kilometers (11 miles) per hour would have shattered the bones of T. rex and other large carnivores like Giganotosaurus,[75] though one counterargument in 2019 also discusses how T. rex and other tyrannosaurids were at least more maneuverable and agile compared to allosauroids, and thus would not have been subject to the exact same arguments.[76]
One T. rex charges out of hiding at an Edmontosaurus
“ Time to spring the trap. One T. rex rushes out! The herd panics, and bolts to where the other T. rex is waiting... in ambush. ”
A study in 2021 calculated a rhythmic, energy-efficient walking speed of 1.28 meters (4 feet, 2 inches) per second, or 4.6 kilometers (3 miles) per hour for T. rex.[19][20] With this being the current consensus regarding T. rex's speed, it likely hunted its prey via ambush, since some of them, like Edmontosaurus, are believed to be twice its speed, as stated in the fifth segment of Swamps, the likely basis of this being a study in 2009, which indicates that Edmontosaurus can reach a speed of 15.7 meters (52 feet) per second, or 57 kilometers (35 miles) per hour, when galloping on all fours, and 14 meters (46 feet) per second, or 50 kilometers (31 miles) per hour, when running on two legs,[77] double the speed of the results that consistently come up in modern T. rex speed calculations. However, Dr. Darren Naish later clarified that the idea of Edmontosaurus being twice as fast as T. rex was an error, and both animals actually had a similar top speed, meaning that, given the modern estimates of the maximum speed of T. rex (which was calculated almost a decade after the studies regarding the running speed of Edmontosaurus, and thus, are more in-line with the current understanding of these animals), Edmontosaurus likely also ran at speeds of around 25 - 30 kilometers (15.5 - 19 miles) per hour, making it easier for a T. rex to catch up to one of these hadrosaurs.[DN 4] Although ambushing prey is more preferable for predators since it would help conserve effort, energy, and time, the fact that at least two cases show T. rex biting an Edmontosaurus on the tail imply that the robust theropod is not averse to chasing after prey when necessary (and also that Edmontosaurus is not fast enough to escape unscathed at all times), as tail bites are more likely inflicted by a predator attempting to grab its fleeing target from behind during a pursuit.[56][57]
A T. rex by the coast of the Western Interior Seaway
On Prehistoric Planet, Tyrannosaurus rex is depicted with mottled brown and cream skin, providing the hunter a degree of countershading (which many animals, predator and prey alike, use to enhance their camouflage depending on the light and angle at which they are viewed). It has distinctive streaks of color along its mouth that resemble external teeth, with its actual teeth covered with fleshy lips. Of note, on the show, the skin patterns of T. rex very faintly resembles that of its Asian relative Tarbosaurus, showing the connection between the two. As with the other tyrannosaurs featured on Prehistoric Planet, T. rex bears stripes on its snout, and it has been theorized that this is a trait that they all inherited from their last common ancestor. While there is no confirmation of this being the case, Dr. Darren Naish shared this fan theory, indicating a degree of support and plausibility for the idea.[DN 5]
The show also depicts T. rex with faint sexual dimorphism. Only one adult female is shown in the series, during the second segment of Freshwater, and she is depicted with slightly less-prominent eye crests as well as slightly lighter skin color (fitting given how, in most animals, the females have duller coloration compared to their more vibrantly-colored male counterparts), though this can also be attributed to her being younger than the old male she met as well as individual variation.
The T. rex skeleton in the opening of the first season's episodes
“ Surely, one of the most remarkable animals that have ever existed - and certainly one of the most famous - is a dinosaur. Tyrannosaurus rex. An animal to spark the imagination for all of us. What kind of an animal was it? What did it look like? How did it live? ”
― David Attenborough, Prehistoric Planet Season 1 episode opening
T. rex is also the subject of two Uncovered segments, the first being "Could T. rex Really Swim?", which discusses the idea of large theropods swimming, and the second being "How Good Were T. rex Senses?", which explains in great detail the acute senses that made T. rex such a formidable hunter. Footage of T. rex facing off against the two Quetzalcoatlus in the first segment of North America is also used for the Uncovered segment "What Else Lived Alongside The Dinosaurs?", specifically the part regarding pterosaurs. Additionally, T. rex is featured in "Pterosaur Beach", the first episode of Prehistoric Planet Immersive, with two young T. rexes disturbing a colony of pterosaurs on a coastline until the arrival of their parent.
Tyrannosaurus rex lived 68 - 66 million years ago in Laramidia, an island continent that would one day become western North America, which, by that time, was nearly split in half by an inland sea. Its range goes as far north as Canada, all the way down to at least New Mexico and Texas in the south, as indicated by fossils in the Javelina Formation. While T. rex appears to prefer subtropical inland forests, swamps, rivers, and open plains (all the aforementioned environments are seen in the Hell Creek Formation, which, though warmer than Montana and South Dakota today, was kept humid by sufficient levels of rainfall), T. rex remains have also been found in coastal and even semi-arid regions like the Javelina Formation.
The origin of Tyrannosaurus rex is still not entirely clear. There was once the idea that T. rex descended from North American tyrannosaurines like Daspletosaurus, though the current prevailing theory is that T. rex came from Asian tyrannosaurines like Tarbosaurus of Mongolia or Zhuchengtyrannus of eastern China.[78] In 2024, however, a newly-described species, Tyrannosaurus mcraeensis of the Hall Lake Formation in the McRae Group of New Mexico, once again supports the theory that T. rex descended from North American tyrannosaurines. Tyrannosaurus mcraeensis lived approximately 73 - 71 million years ago, around 3 - 5 million years before T. rex first appeared, possessing a less-prominent chin, a shallower lower jaw (which likely provides a weaker bite force), blunter teeth, and a slightly less-robust build more in line with Tarbosaurus and Zhuchengtyrannus, thus also lending some credence to the idea that Tyrannosaurus descended from Asian ancestors that crossed a land bridge. It should be noted, however, that the differences in jaw shape indicate that T. mcraeensis is not necessarily the direct ancestor of T. rex, which may have descended from another undiscovered Tyrannosaurus species that lived at the same time as T. mcraeensis. Furthermore, as a relatively recent discovery, the validity of T. mcraeensis is still debatable. Dr. Thomas Carr, a paleontologist who primarily focuses on tyrannosauroids, considers the new study "unpersuasive", suggested that the supposed differences of the specimen with T. rex can simply be attributed to the animal's age and individual variation, and added that, as the animal's 73 - 71 million years of age was based on the rock beneath it and not on the skull itself, there is no proper evidence to suggest that Tyrannosaurus appeared earlier than 68 million years ago.[1][2]
Paleofauna[]
A selection of non-avian dinosaurs that lived in the Hell Creek, Lance, and Scollard Formations (T. rex on the left side, in dark red)
“ Here, in spring, new plant growth creates new feeding grounds for the gathering herds. But where there are large numbers of plant-eaters, there are great hunters... ”
No matter the region (as long as it is land-based), Tyrannosaurus rex dominated as the apex predator, with most of the other predatory niches between the adults and small carnivorous dinosaurs being filled in by young T. rexes of various growth stages. Given its status as top hunter, T. rex would have been one of the most widespread and most successful animals within its range, with studies in 2021 postulating that around 20,000 adult T. rexes would have been alive at any given time, resulting in a total of 2.5 billion T. rexes existing throughout their three million years of existence.[79][80] However, various uncertain factors like variability in body sizes, habitat preferences, survival rates, and others make the theories put forth by these population studies questionable.[81][82] Regardless, T. rex would have coexisted with animals like Ankylosaurus, Edmontosaurus, Pachycephalosaurus, and Triceratops, as well as some dromaeosaurs like Acheroraptor, troodontids like Pectinodon, and the medium-sized azhdarchid pterosaur Infernodrakon. In its southern range, T. rex would have lived alongside similar animals like the chasmosaurine ceratopsian Bravoceratops, the saurolophine hadrosaur Kritosaurus, the dromaeosaurid Saurornitholestes, and troodontids, but such ecosystems also have more peculiar creatures like Alamosaurus (the only sauropod in North America following around 30 million years of sauropod absence on the continent) and the only other predator that could possibly challenge an adult T. rex, the azhdarchid Quetzalcoatlus northropi, one of the largest pterosaurs ever known.
In a 2011 study that estimated the proportions of large-bodied dinosaurs in the Hell Creek Formation, it was revealed that Tyrannosaurus rex made up 24% of the dinosaurs found in Hell Creek, being second only to Triceratops, which makes up 40% of Hell Creek's dinosaur population. T. rex was followed by Edmontosaurus, which made up 20% of Hell Creek's dinosaur population.[83]
As one of the last non-avian dinosaurs, T. rex, along with most of the animals it coexisted with, would have bore witness to the Cretaceous-Paleogene Extinction Event 66.043 million years ago,[84] a catastrophe that ultimately wiped out three-quarters of all life on Earth, including all non-avian dinosaurs.
Hunting Tactics and Feeding Preferences[]
A T. rex alongside a freshly-slain Triceratops
“ T. rex are built for hunting large herbivores, and many of those have evolved heavy defensive weapons. ”
Tyrannosaurus rex is the apex predator of its environment. With its six-ton bone-crushing bite, it can overcome heavily-armored prey like Triceratops and Ankylosaurus, though there is also a good chance that, even if a T. rex survives its encounters with such dangerous prey, it will not come out of these encounters unscathed, with gore, infection, and even broken bones being possible risks. While known for its brute force, as a theropod, T. rex possesses predatory cunning and tactics. In order to hunt an Edmontosaurus successfully, two T. rex brothers stalked a herd of them in the darkness of the night, deliberately causing noise while hidden in the cover of the forest to cause the herd to panic and eventually separate, isolate, and ambush one member, similar to how a few Dromaeosaurus successfully caused an Edmontosaurus herd to hastily cross a rapid icy river in the first segment Ice Worlds (resulting in the death of at least one member), and how T. rex's Alaskan relative Nanuqsaurus relied on spreading panic to cause an Ornithomimus to eventually make a critical mistake that guaranteed its capture in the fifth segment of North America.
Wherever tyrannosaurs ruled, their juveniles tend to occupy the various predatory niches between the adult tyrannosaurs and other hunters. Although the youngsters tend to lack the bone-crushing capabilities of their more mature counterparts, they are still deadly hunters in their own right. One of the most significant fossils of any dinosaur is the "Dueling Dinosaurs" specimen of Hell Creek, which preserves an adolescent T. rex locked in combat with a Triceratops horridus. Entombed in sandstone, the two skeletal remains are considered to be one of the most preserved and most complete specimens of both T. rex and Triceratops, showcasing the sort of prey Tyrannosaurus went after and what sort of threat it posed, even when not fully mature.[85][86]
A pair of subadult T. rex brothers observing herds of herbivores visiting the swamplands of the Hell Creek Formation
“ A group of Edmontosaurs. They lack armor, but they're as big as T. rex, and twice as fast. To catch one needs cunning. ”
Due to its great physique being built more for power than speed, Tyrannosaurus, like its earlier relative Daspletosaurus, likely preferred to go after slower, more heavily-armed prey. In the second segment of Freshwater, T. rex is seen feeding on a Triceratops starting from the neck. As a study in 2012 suggests, T. rex likely focused on the nutrient-rich neck muscles behind the frill of a Triceratops (which, in life, were necessary to help the ceratopsian support the great weight of its head).[87]
Even so, these muscular theropods are still very much capable of going after lighter, quicker prey, with the fifth segment of Swamps showing them relying on smart tactics like hunting at night, ambush, and, on occasion, even cooperative hunting to tackle the challenges posed by fast-moving prey. It is also important to note that even Edmontosaurus, which is supposedly one of the easier targets to tackle, is not the defenseless pushover that popular culture makes it out to be. Given its size and mass, Edmontosaurus is a powerful animal capable of fighting off attackers with its muscular limbs and tail. Evidence of this can be seen in DMNH 1943, an Edmontosaurus annectens specimen with a U-shaped T. rex bite on its tail that shows signs of healing, indicating that the animal escaped and survived the attack (and may have potentially fought the T. rex off).[56] A similar case from the Hell Creek Formation was brought in 2013, involving a T. rex tooth embedded in a pair of traumatically fused Edmontosaurus annectens tail vertebrae, which clearly indicates that the victim got away from its attacker (albeit suffering extensive bone infection afterward) and survived given how the predator's tooth was surrounded by healed bone growth. The study states that tail bites indicate that T. rex was capable of pursuit predation, as such injuries were likely inflicted as the theropod chased after its prey, attempting (and failing) to grab the hadrosaur to prevent it from escaping.[57] The original plan for the fifth segment of Swamps even involved two juvenile T. rexes attacking an adult Edmontosaurus, only to be beaten up.[DN 7] While this particular idea ultimately never came to pass, the final version of events showed that it still takes a considerable amount of experience, skill, and even luck for a T. rex to bring down an Edmontosaurus.[DN 8]
A T. rex comes across a dead turtle
“ The island offers safety and the promise of food. Giant, two-tonne turtles are here to nest. But this is the one that has drawn him here. It's dead, and the tyrannosaur has smelt its rotting body. If he can just get to the underbelly, he will have over two thousand pounds of easy meat. ”
As a predator, T. rex would have been opportunistic, not averse to scavenging any sufficiently-sized carcass it comes across to save effort and energy. In the first segment of Coasts, a T. rex risks his life (and that of his five hatchlings, one of which gets eaten by a mosasaur) to reach an island where there's an already-dead turtle he can feast on without any effort. in the first segment of North America, a T. rex also closes in on the smell of a dead Alamosaurus to feed on it, driving away a trio of troodontids in the process, though the T. rex himself ends up getting challenged by a pair of Quetzalcoatlus, which also take advantage of the great feeding opportunity. However, while it is capable of doing so, T. rexes cannot primarily rely on scavenging since is not as easy as it seems to be, especially given how T. rex lacks the ability to fly like vultures, and corpses are not a readily-available resource that is consistently within reach. A study published in 2016 ran several models testing the idea of body size affecting scavenging efficiency, with the results pointing out that scavenging is most efficient for animals around 27 - 1,044 kilograms (60 - 2,302 pounds) with an average of 428 kilograms (944 pounds). For large carnivores like T. rex and Giganotosaurus, both of which weigh over 8 metric tons (8.8 short tons), energy invested in scavenging would actually outweigh the energy they would gain from it, as the need to move their large bodies around to search for dead animals consistently would have ended up taking its toll on them. For this reason, they would have needed to obtain their food in other ways; it is more preferable for them to target, plan, and take their chances hunting live prey. Hell Creek would have also been unable to meet the minimum energy requirements for any scavenger close to T. rex's size.[88]
Juvenile T. rexes squabbling over a baby turtle
“ And if all else fails, you can always steal supper from someone else. ”
T. rex would have also been able to engage in kleptoparasitism, the act of stealing the food of others, but this, too, would have been impractical for an adult T. rex to rely on as the primary means to feed itself, as no other predator in its range ever approached its size, and thus would not have been able to kill sufficiently-sized prey to regularly feed a carnivore as large as it. If a T. rex were to ever rely on stealing already-dead animals being scavenged by other carnivores, it would simply end up facing the same problems as scavenging, and, while T. rexes may occasionally also fight and kill each other over food, regularly relying on the robbing of other T. rexes is inefficient in cost for similar reasons, also making that tactic unstable compared to alternative means of feeding. Hunting is risky, with Prehistoric Planet itself stating in the fourth segment of Forests and the fourth segment of Oceans that most hunts are more likely to fail than succeed (due to prey escaping, prey successfully retaliating, or other factors that affect the hunt), but all carnivores in Earth's history have managed to thrive for varying amounts of time, mainly by evolving adaptations and adopting tactics needed to compensate for their shortcomings and tackle their prey; in T. rex's case, it evolved its powerful jaws to attack large animals as well as crush through the defenses of more heavily-armed targets like Triceratops and Ankylosaurus, and, to compensate for its slow speed,[21][75] it can rely on ambush, as is the case for many predators that are slower than their prey. Because of these reasons, coupled with the fact that fossils preserve healed wounds inflicted by a T. rex (showing that it would attack live animals),[56][57] the already-controversial notion that multi-ton carnivores like T. rex are primary - much less obligate - scavengers has long been considered infeasible.
Social Behavior[]
A female (right) approves and reciprocates the intentions of the male to mate
In terms of social behavior, there is barely any direct evidence for such in Tyrannosaurus, which appears to be a mostly solitary animal. Nevertheless, tyrannosaurs seem to show some evidence of pack behavior, with an Uncovered segment dedicated to proof of pack-hunting in relatives like Nanuqsaurus, and fossils from South Dakota revealed three T. rexes within close proximity of each other.[89] The fifth segment of Swamps reflects the idea that dinosaurs maintained family ties throughout their lives by showing two subadult Tyrannosaurus brothers hunting prey together.[PhP 3][DN 6]
Additionally, there are instances where individuals may encounter each other and not immediately engage in hostilities. In such cases, initial contact may be tense, but it can transition into courtship and mating, as depicted in the second segment of Freshwater. The male T. rex is shown rearing up and displaying his throat, to make him appear tall and powerful to any observing females, while also showing his vulnerability (in a form of trust) and non-aggression (similar to how crocodilians display their throats to indicate that they have no hostile intent).
A male (left) and female nuzzle each other
“ The facial area of a tyrannosaur is very sensitive to touch, and they nuzzle. His great size and his battle scars are evidence that he is a survivor. And that, perhaps, in her eyes, makes him an attractive partner ”
The snouts of tyrannosaurs contain numerous nerve endings, facilitating face-to-face interactions, whether they are intimate or aggressive in nature (evidence of aggressive interaction comes in the form of several facial bite marks found on various theropods, while rubbing an nuzzling behavior can still be seen in reptiles today, like crocodiles and monitor lizards).[DN 9] During mating, T. rexes are depicted assuming a sitting position, similar to the posture observed in present-day birds and reptiles, rather than the long-held belief of a standing position.
“ So, they stay together, and, in the coming weeks, they mate frequently. Eventually, she'll lay up to 15 eggs, and with them comes the promise of the next generation. ”
Due to a lack of evidence, it is unclear whether tyrannosaurs went their separate ways after mating, or stuck together at least for a while to raise their brood. Given the state of most fossil finds, it appears that such partnerships were only temporary, and outside of the mating season, tyrannosaurs lived alone, matching the behavioral patterns of tigers today.
Parental Habits[]
Prehistoric Planet - Official Sneak Peek
“ A full grown T. rex is the planet's most powerful predator, but today he's just being father. ”
Because of the rarity of fossilized tyrannosaur nests and juveniles, the parental habits of Tyrannosaurus are not exactly clear. To this day, there is no direct evidence to support or deny the various ideas regarding how juvenile T. rexes are raised, be it by one parent, both parents, or no parents. Assuming at least one parent raised the hatchlings, it is not known how long they reared them either.
Even so, based on crocodiles, birds, other theropods like oviraptorids, and even other dinosaurs that are not so closely related like the hadrosaur Maiasaura, it is possible of T. rex did indeed raise its young. Taking inspiration from some birds, Prehistoric Planet depicts only the male T. rex taking care of his offspring to a degree, though the show depicts T. rex more like an r-selected species, given how it is stated that they spawn at least 15, with around two-thirds dying off in their first year (r-strategist animals rely on spawning multiple offspring, many of which are expected to perish before reaching adulthood). The T. rex in the first segment of Coasts is also shown leading their children around to safer places where more food can be found, but does not seem to provide extensive parental care, for, unlike Pectinodon and Nanuqsaurus, two theropods on the show that still provide food for their hatchlings (and thus appear to be K-strategists, animals that provide extensive parental care to their offspring), T. rex refuses to share the turtle he scavenged with his children, forcing them to find food on their own. This aspect also seems to be in-line with the r-selection strategy, which involves a lesser degree of parental care.
T. rex refuses to share his meal with his hatchlings
“ The young are keen for a taste, but he's not sharing it. It's time for them to learn to hunt for themselves. ”
Even so, this lessened degree of guidance and assistance can also be a good parenting tactic in its own right. In forcing the juveniles to get their own food rather than sharing meals with their parent, they are encouraged to learn and develop the necessary skills for survival and self-sufficiency early on. Having lead them to an offshore island where food is plenty, the T. rex in the first segment of Coasts at least ensured that his chicks can practice their skills in peace and safety. As they grow older, the juveniles may potentially even assist their parent in the hunt, and eventually, fend for themselves as fully-independent individuals.
Competitive Behavior[]
A mosasaur turns towards a family of T. rexes, viewing them as vulnerable prey
“ But 66 million years ago, venturing into coastal waters would not have been without risk, even for T. rex. Mosasaurs hunted beneath these waves, and young tyrannosaurs, particularly, would have been a valuable meal for these formidable aquatic hunters. T. rex may have been strong swimmers, but they could only have been brief visitors to the prehistoric oceans. Although their name means 'Tyrant Lizard King', they could never have ruled the waves while the mosasaurs patrolled the coasts. ”
In terms of the competition with other carnivores, despite being the apex predator of North America, T. rex has its fair share of opponents. As shown in the first segment of Coasts, when in the sea, T. rex could potentially face mosasaurs, which, at twice its size and mass, are the largest predators of Earth during the Late Cretaceous Period. However, an adult T. rex can still defend itself in the water very effectively, so the mosasaur wisely picked off one of the tyrannosaur's five juveniles instead.
A pair of Quetzalcoatlus annoying and harassing a T. rex
“ Not many can intimidate North America’s top predator, T. rex, whose size and bite are a deadly combo — except for a giant winged foe. ”
― The official Apple TV+ episode synopsis for North America
T. rex could also potentially get into conflict with the giant azhdarchid Quetzalcoatlus, as seen in the first segment of North America, where two of the pterosaurs challenged a T. rex for feeding rights to an Alamosaurus carcass. T. rex weighs 30 - 40 times greater than the lightweight pterosaur, has a powerful, six-ton bite that can crush bone, and, being capable of short bursts of speed as well as walking at a decent pace, it is by no means a lumbering animal.[19][20] In the first segment of North America, a lone Quetzalcoatlus appeared a bit hesitant to approach a T. rex head on, though it slowly tried to creep in when the T. rex had its back turned, implying that it was still ready to try its chances even on its own. When a second Quetzalcoatlus arrived, however, the azhdarchids were more willing to exploit the few advantages they do have to challenge the T. rex. Due to their lighter build, large quadrupedal gait, and competent terrestrial mobility, they can move equally as fast and even be more agile than T. rex on the ground. Their ability to quickly quad-launch into the air at a moment's notice and attack from above is also a definitive advantage, though given the low agility of azhdarchids in the air compared to other types of pterosaurs,[PhP 4] they may need large, open areas like a beach or plain to fully take advantage of their flight capabilities in such a conflict. Quetzalcoatlus also has a six-foot beak that gives it better reach, allowing it to strike opponents from a relatively safe distance. While these do not guarantee that they will always have the upper hand in such situations, with all these traits, Quetzalcoatlus can effectively harass comparatively less-nimble foes and even pose legitimate dangers (like permanent blindness in both eyes, which can be a death sentence for any sight-reliant predator), all of which can prove sufficient to get even the likes of T. rex to leave if the risks they pose outweigh the urgency to feed.
Gallery[]
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It is unknown how exactly dinosaurs drank water. Prehistoric Planet chose to depict various types of dinosaur drinking water in different ways, with theropods shown scooping up water with their lower jaws rather than lapping it with their tongues or sucking it up. In the fourth segment of Deserts, Mononykus, Therizinosaurus, and Tarbosaurus drink water in this manner, and Tyrannosaurus is later depicted doing the same in the second segment of Freshwater.
↑The Complete T. Rex: How Stunning New Discoveries are Changing our Understanding of the World's Most Famous Dinosaur copyright 1993 by John R. Horner: pp 214-215
