Line #3 UsefulNotes/TyrannosaurusRex


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4	[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/rsz_sueskeleton.png]]
5	[[caption-width-right:350:"Sue" on display at the Field Museum of Natural History in Chicago, Illinois. Photographed by [[https://commons.wikimedia.org/wiki/User:Evolutionnumber9 Evolutionnumber9]] and licensed under [[https://creativecommons.org/licenses/by-sa/4.0/deed.en CC BY-SA 4.0]].]]
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7	->''"This is ''the'' theropod."''
8	-->-- '''Gregory S. Paul'''
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10	There's no doubt that ''Tyrannosaurus rex'' is, by far, the most famous of the [[SmallTaxonomyPools stock dinosaurs]], seen as both the most majestic and [[TerrifyingTyrannosaur most terrifying]] of them all. Let's learn a bit more about this incredible animal, shall we?
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12	* '''Name:''' Whereas most dinosaurs are known outside paleontological circles only by their genus, ''T. rex'' is known by its full binomium. ''Tyrannosaurus'', the genus name, comes from the Greek ''tyrannos'', meaning "tyrant", and ''sauros'', meaning "lizard". ''Rex'', the specific name, meanwhile, is Latin for "king", therefore the whole name translates to "tyrant lizard king". As per the rules of binomial nomenclature, the genus name should be spelled with a capital T, whereas the species name should be spelled with a lowercase r. And the correct abbreviation of the name is ''T. rex'', not ''T-rex'' and especially not ''T-Rex''. Early fossils were described under the names ''Dynamosaurus imperiosus'' and ''Manospondylus gigas'' -- both of them are now considered invalid synonyms. A number of other names have also become invalid synonyms of ''Tyrannosaurus'' over the years, including ''Nanotyrannus'', ''Stygivenator'', and ''Dinotyrannus''. Most of these were formerly believed to be dwarf ''T. rex'' relatives for their slender frames and narrower snouts until scientists realized that juvenile ''T. rex'' simply lacked the heavy skulls and robust bodies of the grown-ups. In 2024, a second species of ''Tyrannosaurus'' was named from a partial skeleton found in New Mexico, dubbed ''T. mcraeensis'' ("tyrant lizard of the [[https://en.wikipedia.org/wiki/McRae_Formation McRae Formation]]"). This species seemingly lived a few million years earlier than ''T. rex'' and may have been ancestral to it.
13	* '''Discovery:''' The first ''T. rex'' fossils were found in 1874, but were not recognized as ''T. rex'' until many decades later. The species was officially described by Henry Farfield Osborn in 1905, based on a partial skeleton found by Barnum Brown in Hell Creek, Montana. In the same paper describing ''T. rex'', Osborn described the fossils of another large carnivore, found in Wyoming, as ''Dynamosaurus imperiosus'' ("ruling power lizard"), but later realized that the two belonged to the same species (the rules of scientific naming say the first name is gets priority, and ''T. rex'' beat ''Dynamosaurus'' to seniority by only a few pages). The most complete ''T. rex'' skeletons were found [[UsefulNotes/PrehistoricLifeDinosaurs in 1990 and 1992]], and were dubbed as "[[http://en.wikipedia.org/wiki/Sue_(dinosaur) Sue]]" and "[[http://en.wikipedia.org/wiki/Stan_(dinosaur) Stan]]". These two fossils helped us get a much more accurate image of what the species was like.
14	* '''Classification:''' It was generally believed for most of the 20th century that ''Tyrannosaurus'' was closely related to other giant, carnivorous theropod dinosaurs, such as ''Allosaurus'' and ''Megalosaurus'', as part of the group Carnosauria. However, studies in the 90s revealed ''T. rex'' to in a fact be a part of the group Coelurosauria, which includes many small, feathered theropods, like ''Ornithomimus'', ''Compsognathus'', ''Velociraptor'', and ''Archaeopteryx'' as well as modern birds. Within Coelurosauria, ''T. rex'' was part of the family Tyrannosauridae. Notable tyrannosaurids include ''Tarbosaurus'' (sometimes considered as an Asian ''Tyrannosaurus species'', ''T. bataar''), ''Albertosaurus'', ''Daspletosaurus'', ''Nanuqsaurus'', ''Teratophoneus'', and ''Alioramus''. They were part of the superfamily Tyrannosauroidea, whose notable members include ''Alectrosaurus'', ''Bistahieversor'', (both sometimes considered true tyrannosaurids) ''Dryptosaurus'', ''Moros'', ''Eotyrannus'', ''Dilong'', ''Stokesosaurus'', ''Yutyrannus'', ''Guanlong'', and ''Proceratosaurus''. Also possibly within Tyrannosauroidea are the megaraptorans (named for their most famous member ''Megaraptor''), a group of theropods primarily found in the Southern Hemisphere with slender skulls and massive arms ending in talon-like claws likely used in killing prey -- though they may have instead been carnosaurs or a more primitive group of coelurosaurs.
15	* '''Time period:''' ''T. rex'' lived at the very end of the Cretaceous period, 68-66 million years ago (a time known as the Maastrichtian age). As one of the very last non-bird dinosaurs, it was around to experience the infamous asteroid collision that ended the Mesozoic era. Any depiction of ''T. rex'' earlier than that is, therefore, inaccurate. ''T. mcraeensis'' lived between 3 and 5 million years earlier than ''T. rex''.
16	* '''Range:''' ''T. rex'' was an exclusively North American species. During the Late Cretaceous, North America was divided into two smaller continents by a shallow sea named the Western Interior Seaway; ''T. rex'' lived on the western continent, dubbed Laramidia. Its fossils have been found throughout Laramidia, ranging from Alberta and Saskatchewan in the north to Texas and New Mexico in the south, possibly even as far as Sonora, Mexico. However, its closest relative was was the aforementioned ''Tarbosaurus'', which lived in East Asia at the same time. It is theorized that because of how closely related it was to its Asian counterpart, ''T. rex''[='=]s ancestors likely originated from Asia and crossed over the Bering Strait land bridge into North America, eventually taking over most of Laramidia. ''Albertosaurus'', which lived in Laramidia before this, became extinct shortly after ''T. rex'' appeared, lending credence to this theory. This, however, came into question with the naming of ''T. mcraeensis'', raising the possibility that ''T. rex'''[='=]s ancestors actually originated in North America and instead entered Asia.
17	* '''Size:''' ''T. rex'' was famous for being one of the largest theropods, rivalling notorious contenders ''Giganotosaurus'' and ''Spinosaurus'' in length and likely being heavier than either. The "Sue" skeleton is 12.3 to 12.8 m long (the inaccuracy comes from a few missing vertebrae), about 4 m tall at the hip, and is estimated to weigh 8.4 to 14 metric tons (for comparison, that's 2 to 3 times the weight of an African bush elephant). It was also much bulkier in real life compared to the athletic, "cut"[[note]]With lots of muscle striations showing[[/note]] manner that fiction and older reconstructions tend to depict it with. As a result, it probably wasn't very fast (current estimates of its top speed generally agree on somewhere between 18-24 km/h), but given that most of its usual prey was also large and bulky, it didn't have to be.
18	* '''Posture:''' Early restorations depicted ''T. rex'' in a kangaroo-like tripod posture, dragging its long tail on the ground like Godzilla. However, thanks to more complete skeletons, now we know that it held its body horizontally, balancing its body and huge head with its powerful tail.
19	* '''Big head:''' ''T. rex'' had a massive head, even in comparison to other big, predatory theropods. Its mouth was full of sharp teeth, up to 20 cm (8 inches) long, sometimes dubbed "killer bananas" because of their size and shape. Its bite force is estimated to be about 8,000 pounds, stronger than any other known land animal, which it needed to crush the bones of the large, often armored dinosaurs it ate.
20	* '''Puny arms:''' One of the most iconic, and most ridiculed, traits of ''T. rex'' is its tiny arms (though many theropods had proportionately even ''smaller'' arms). They were two-fingered with sharp claws on them, and the palms faced inward (rather than downward, as often erroneously depicted). The reason for the arms' small size is mainly practicality; large arms would have gotten in the way of ''T. rex'''s bite, which was the dinosaur's primary killing tool. Thus, whereas other predators have clawing weapons to complement their teeth, ''T. rex'' put all its power into its jaws. But even in spite of their size, the arm bones show signs of large muscle attachment (a hallmark of coelurosaurian ancestry) and thus, they were very strong and capable of lifting up to 200 pounds (90 kilograms). Because of this, ''T. rex'' might have used them to hold onto struggling prey while it dispatched it with its jaws. In addition, they could have also been used to help lift ''T. rex'' up from a sleeping position when it was waking up, hold onto a mate while copulating, or even to pick up its offspring the same way a crocodile uses its jaws to carry its babies.
21	* '''Hunter or scavenger?:''' Though the ''T. rex'' is typically portrayed as a hunter in media, there is an infamous debate among paleontologists as to whether or not ''T. rex'' was actually a scavenger instead, popularized by paleontologist and ''Film/JurassicPark'' dinosaur consultant Jack Horner. While proponents of the "scavenger" theory point to ''T. rex''[='=]s slow speed, ability to crush bone, and acute sense of smell, the overwhelming majority of experts believe ''T. rex'' was primarily a hunter, as evidenced by its potential prey also being fairly slow, its superb hearing and eyesight, its massive caloric requirements, and the existence of plant-eating dinosaur fossils with ''T. rex'' bite marks on them that show signs of healing (indicating they survived a ''T. rex'' attack). However, ''T. rex'' would have also definitely eaten any carrion it came across, and it's possible that large, adult ''Tyrannosaurus'' would regularly KillSteal the hunts of other carnivores, including rival ''T. rex''. Modern predators, like tigers and great white sharks, also do this, especially in old age. That said, ''T. rex'' regularly hunted some formidable prey -- heavily armored animals like ''[[TemperCeratops Triceratops]]'' and ''[[ToughArmoredDinosaur Ankylosaurus]]'', as well as herd-moving behemoths like ''[[SocialOrnithopod Edmontosaurus]]'' and ''[[GentleGiantSauropod Alamosaurus]]''. On the other hand, young ''Tyrannosaurus'', with their slenderer bodies and narrower snouts, hunted faster-moving and more delicate mid-sized animals like ''Ornithomimus'', ''Thescelosaurus'', ''Leptoceratops'', and ''Pachycephalosaurus''. Bite marks on ''T. rex'' bones attributable to other ''T. rex'' also suggest it may have [[MonstrousCannibalism even been cannibalistic]]. ''T. rex'' most likely hunted by ambush, using a short burst of speed to catch prey before using its massive body to knock the victim over and finishing them off with their powerful jaws.
22	* '''Feathers or scales:''' Historically, ''T. rex'' was portrayed with lizard- or crocodile-like scaly skin. But with the discovery that many dinosaurs, particularly coelurosaurs (including the tyrannosauroids ''Yutyrannus'' and ''Dilong''), were feathered, it's been suggested that ''T. rex'' was too, basically looking like a giant toothy bird. However, fossilized skin impressions of ''T. rex'' and other tyrannosaurids show that most of its body was, indeed, scaly (or at least, extremely sparsely feathered); the only place that was potentially fully feathered was its back, similar to the mane of a lion. As ''T. rex'' was a large animal living in warm climate, it likely did not need the extra insulation from a thick coat of fluff, just as similarly-sized mammals like rhinoceroses and elephants are sparsely haired. Some still speculate that it had downy feathers as a hatchling, when it was still small enough to need insulation, and eventually lost these as it reached a certain age and size, much like a baby penguin molting away its birth feathers as it becomes an adolescent.
23	* '''Sound:''' ''T. rex'' is typically depicted in media with a MightyRoar; ever since ''Film/JurassicPark'', everyone "knows" what that roar sounded like. However, there is actually little evidence that ''T. rex'' could roar the same way a lion or a bear could, since it lacked the vocal organs that allow mammals to do so. It may have instead produced low-pitched rumbling, hissing, and bellowing, similar to crocodilians, large flightless birds (like ostriches and cassowaries), and bitterns. It still would've sounded pretty damned impressive, although it may have been bit underwhelming for those used to the movies. Basically, imagine the sound an alligator makes, then imagine if that alligator was 40 feet long and weighed over 8 tonnes. Furthermore, the vibrations produced by a communicating ''T. rex'' may have been deep and powerful enough to have been ''felt'' when they rippled through the air, possibly even creating small tremors in the earth.
24	* '''Senses:''' ''T. rex'' had extraordinary senses of smell and hearing. Analysis of the braincase in fossilized skulls shows that it had large olfactory bulbs and a long cochlear duct capable of receiving low-frequency sounds. These traits would have been advantageous both as a predator (tracking and listening for prey) and as a scavenger (finding carrion from a great distance and detecting approaching rivals). However, contrary to what [[Film/JurassicPark Steven Spielberg]] and [[Literature/JurassicPark Michael Crichton]] would have you believe, ''T. rex'' also had excellent eyesight that would've let the creature spot objects from as far as six kilometres with thirteen times the detail. It had large eyes facing forward connecting to big optical lobes, and a relatively narrow snout, allowing for binocular vision. This is probably ''T. rex's'' most unique trait, as almost no other dinosaur had vision like this (most other large, predatory theropods have poor eyesight and relied mainly on their sense of smell). This ability supports the idea that ''T. rex'' was a hunter, as binocular vision is beneficial when chasing prey.
25	* '''Intelligence:''' Most early depictions of ''T. rex'' have them as solitary brutes with little in the way of brainpower or social ability. More recent studies have shown that ''T. rex'' had a bigger brain-to-body ratio than previously thought, being smarter than earlier species of giant theropods. In fact, some studies (albeit controversial ones) suggest ''T. rex'' may have had an intelligence similar to wolves, or even ''baboons'', which would have made it one of, if not ''the'', smartest non-avian dinosaurs. Given its adaptations and how its common prey items included some heavily armored and highly social animals, it's likely ''T. rex'' would need the intelligence to be able to take down its prey with different strategies and [[KnowWhenToFoldEm know when to throw in the towel]] and eat a pre-killed carcass instead. Some scientists have also proposed that ''T. rex'' [[BadassCrew hunted in packs]], but the idea of such coordinated behavior in predatory dinosaurs is controversial, as birds of prey and crocodiles typically do not hunt socially.
26	* '''Neighbors''': In art and fiction, ''T. rex'' is often portrayed living alongside dinosaurs it didn't coexist with in reality. The most egregious cases show it alongside Jurassic dinosaurs like ''Stegosaurus'', but even authors who try to do their homework often slip up by showing ''T. rex'' coexisting with Late Cretaceous North American dinosaurs that lived about 5-10 million years earlier in the Campanian age, like ''Parasaurolophus'' and ''Styracosaurus''. Dinosaurs that did live with ''T. rex'' in Maastrichtian-aged North America 68-66 million years ago include ''Triceratops'', ''Ankylosaurus'', ''Edmontosaurus'', ''Alamosaurus'', ''Dakotaraptor'', ''Pachycephalosaurus'', ''Ornithomimus'', ''Torosaurus'', ''Denversaurus'', ''Thescelosaurus'', ''Leptoceratops'', ''Anzu'', ''Acheroraptor'', ''Pectinodon'', and ''Trierarchuncus''. With the possible exception of "Nanotyrannus", no other tyrannosaurs shared ''T. rex'''s ecosystem, making it the undisputed apex predator of its environment (the next largest predator ''Dakotaraptor'' was 4-6 m long and weighed 220-350 kg, making it far too small to compete with an adult ''T. rex''[[note]]The validity of ''Dakotaraptor'' has also been challenged by a number of palaeontologists, with suspicions that it may be a chimera.[[/note]]). Also found in ''T. rex''[='=]s habitat were the giant pterosaur ''Quetzalcoatlus'', the amphibious reptile ''Champsosaurus'', small mammals (such as the semiaquatic marsupial relative ''Didelphodon'' and the possible early primate ''Purgatorius''), birds, crocodiles, turtles, snakes & lizards, amphibians, and a variety of fish (including freshwater sharks and rays, gars, bowfins, sturgeons, and paddlefish). It also would've coexisted with very large mosasaurs (around the same size as ''T. rex''), but these were probably limited to coastal and marine waterways.
27	* '''Environment''': The prehistoric North American range of ''T. rex'' was divided between a swampy subtropical forest to the north and arid inland plains to the south, with the nascent Rocky Mountains to the west. These environments supported different faunas. The former, known as the Lancian fauna and most famously represented by the Hell Creek Formation of Montana, was dominated by ''Triceratops'', ''Edmontosaurus'', and ''Ankylosaurus'', while the latter, the less-studied Sanjuanian fauna (known primarily from the Ojo Alamo Formation of New Mexico), was dominated by ''Alamosaurus'', ''Torosaurus'', and ''Quetzalcoatlus''. Most of ''T. rex'''s contemporaries mentioned above are Lancian, with many having Sanjuanian counterparts -- ''Ojoraptorsaurus'' instead of ''Anzu'', ''Dineobellator'' instead of ''Acheroraptor'', ''Glyptodontopelta'' instead of ''Ankylosaurus'', ''Ojoceratops'' instead of ''Triceratops''[[note]]Although ''Ojoceratops'' has been suggested by some researchers to be a synonym of ''Triceratops''[[/note]], and ''Kritosaurus'' instead of ''Edmontosaurus''. There are also some species without northern counterparts, like ''Alamosaurus'' and a currently unnamed hadrosaur similar to the Campanian-aged ''Corythosaurus''.

Context UsefulNotes / TyrannosaurusRex