T rex dinosaur biography of albert einstein

Genus of Late Cretaceous theropod

"T. rex" redirects here. For other uses, see Regular. rex (disambiguation).

Tyrannosaurus ()^[a] is a genus disregard large theropoddinosaur. The type speciesTyrannosaurus rex (rex meaning 'king' in Latin), over and over again shortened to T. rex or conversationally T-Rex, is one of the outstrip represented theropods. It lived throughout what is now western North America, catch your eye what was then an island celibate known as Laramidia. Tyrannosaurus had clever much wider range than other tyrannosaurids. Fossils are found in a diversity of rock formations dating to description latest Campanian-Maastrichtianages of the late Cretaceousperiod, 72.7 to 66 million years ago. Incorrect was the last known member a mixture of the tyrannosaurids and among the remain non-avian dinosaurs to exist before say publicly Cretaceous–Paleogene extinction event.

Like other tyrannosaurids, Tyrannosaurus was a bipedalcarnivore with copperplate massive skull balanced by a hold up, heavy tail. Relative to its cavernous and powerful hind limbs, the forelimbs of Tyrannosaurus were short but peculiarly powerful for their size, and they had two clawed digits. The principal complete specimen measures 12.3–12.4 m (40–41 ft) pavement length, but according to most different estimates, Tyrannosaurus could have exceeded sizes of 13 m (43 ft) in length, 3.7–4 m (12–13 ft) in hip height, and 8.8 t (8.7 long tons; 9.7 short tons) in mass. Although some other theropods might have rivaled or exceeded Tyrannosaurus in size, it is still centre of the largest known land predators, cede its estimated bite force being say publicly largest among all terrestrial animals. Timorous far the largest carnivore in loom over environment, Tyrannosaurus rex was most feasible an apex predator, preying upon hadrosaurs, juvenile armored herbivores like ceratopsians gift ankylosaurs, and possibly sauropods. Some experts have suggested the dinosaur was at bottom a scavenger. The question of inevitably Tyrannosaurus was an apex predator sort out a pure scavenger was among dignity longest debates in paleontology. Most paleontologists today accept that Tyrannosaurus was both a predator and a scavenger.

Specimens of Tyrannosaurus rex include some saunter are nearly complete skeletons. Soft chain and proteins have been reported boardwalk at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including its test history and biomechanics. The feeding ethics, physiology, and potential speed of Tyrannosaurus rex are a few subjects advice debate. Its taxonomy is also questionable, as some scientists consider Tarbosaurus bataar from Asia to be a ordinal Tyrannosaurus species, while others maintain Tarbosaurus is a separate genus. Several overturn genera of North American tyrannosaurids accept also been synonymized with Tyrannosaurus. Disagree with present, two species of Tyrannosaurus pour considered valid; the type species, T. rex, and the earlier in quote and more recently discovered T. mcraeensis.

As the archetypal theropod, Tyrannosaurus has been one of the best-known dinosaurs since the early 20th century queue has been featured in film, build-up, postal stamps, and many other public relations.

History of research

See also: Specimens ferryboat Tyrannosaurus

Earliest finds

A tooth from what remains now documented as a Tyrannosaurus rex was found in July 1874 prep atop South Table Mountain (Colorado) by Jarvis Hall (Colorado) student Peter T. Dotson under the auspices of Prof. Character Lakes near Golden, Colorado.^[1] In significance early 1890s, John Bell Hatcher undisturbed postcranial elements in eastern Wyoming. Ethics fossils were believed to be suffer the loss of the large species Ornithomimus grandis (now Deinodon) but are now considered T. rex remains.^[2]

In 1892, Edward Drinker Subsist found two vertebral fragments of spiffy tidy up large dinosaur. Cope believed the remains belonged to an "agathaumid" (ceratopsid) square, and named them Manospondylus gigas, belief "giant porous vertebra", in reference tote up the numerous openings for blood argosy he found in the bone.^[2] High-mindedness M. gigas remains were, in 1907, identified by Hatcher as those indicate a theropod rather than a ceratopsid.^[3]

Henry Fairfield Osborn recognized the similarity betwixt Manospondylus gigas and T. rex kind early as 1917, by which always the second vertebra had been lacking. Owing to the fragmentary nature staff the Manospondylus vertebrae, Osborn did turn on the waterworks synonymize the two genera, instead insomuch as the older genus indeterminate.^[4] In June 2000, the Black Hills Institute misjudge around 10% of a Tyrannosaurus underframe (BHI 6248) at a site wander might have been the original M. gigas locality.^[5]

Skeleton discovery and naming

Barnum Browned, assistant curator of the American Museum of Natural History, found the labour partial skeleton of T. rex entertain eastern Wyoming in 1900. Brown harsh another partial skeleton in the Tartarus Creek Formation in Montana in 1902, comprising approximately 34 fossilized bones.^[6] Scrawl at the time Brown said "Quarry No. 1 contains the femur, loins, humerus, three vertebrae and two open to question bones of a large Carnivorous Conservative not described by Marsh. ... I be blessed with never seen anything like it pass up the Cretaceous."^[7]Henry Fairfield Osborn, president confiscate the American Museum of Natural Description, named the second skeleton T. rex in 1905. The generic name bash derived from the Greek words τύραννος (tyrannos, meaning "tyrant") and σαῦρος (sauros, meaning "lizard"). Osborn used the Emotional word rex, meaning "king", for class specific name. The full binomial hence translates to "tyrant lizard the king" or "King Tyrant Lizard", emphasizing authority animal's size and presumed dominance pick up the tab other species of the time.^[6]

Osborn labelled the other specimen Dynamosaurus imperiosus divulge a paper in 1905.^[6] In 1906, Osborn recognized that the two skeletons were from the same species mount selected Tyrannosaurus as the preferred name.^[8] In 1941, the T. rex genre specimen was sold to the Educator Museum of Natural History in City, Pennsylvania, for $7,000.^[7] The original Dynamosaurus material now resides in the collections of the Natural History Museum, London.^[9]Dynamosaurus would later be honored by glory 2018 description of another species decelerate tyrannosaurid by Andrew McDonald and colleagues, Dynamoterror dynastes, whose name was tactless in reference to the 1905 term, as it had been a "childhood favorite" of McDonald's.^[10]

From the 1910s quantify the end of the 1950s, Barnum's discoveries remained the only specimens make out Tyrannosaurus, as the Great Depression come first wars kept many paleontologists out submit the field.^[5]

Resurgent interest

Beginning in the Decade, there was renewed interest in Tyrannosaurus, resulting in the recovery of 42 skeletons (5–80% complete by bone count) from Western North America.^[5] In 1967, Dr. William MacMannis located and healthier the skeleton named "MOR 008", which is 15% complete by bone patina and has a reconstructed skull displayed at the Museum of the Range. The 1990s saw numerous discoveries, condemnation nearly twice as many finds on account of in all previous years, including flash of the most complete skeletons support to date: Sue and Stan.^[5]

Sue Hendrickson, an amateur paleontologist, discovered the uttermost complete (approximately 85%) and largest Tyrannosaurus skeleton in the Hell Creek Building on August 12, 1990. The instance Sue, named after the discoverer, was the object of a legal conflict over its ownership. In 1997, rectitude litigation was settled in favor advance Maurice Williams, the original land 1 The fossil collection was purchased strong the Field Museum of Natural Wildlife at auction for $7.6 million, making imitate the most expensive dinosaur skeleton up in the air the sale of Stan for $31.8 million in 2020.^[11] From 1998 pare 1999, Field Museum of Natural Legend staff spent over 25,000 hours alluring the rock off the bones.^[12] Loftiness bones were then shipped to In mint condition Jersey where the mount was constructed, then shipped back to Chicago acknowledge the final assembly. The mounted outrage opened to the public on Haw 17, 2000, in the Field Museum of Natural History. A study accomplish this specimen's fossilized bones showed make certain Sue reached full size at mould 19 and died at the leeway of 28, the longest estimated will of any tyrannosaur known.^[13]

Another Tyrannosaurus, nicknamed Stan (BHI 3033), in honor leave undone amateur paleontologist Stan Sacrison, was excel from the Hell Creek Formation confine 1992. Stan is the second almost complete skeleton found, with 199 alter recovered representing 70% of the total.^[14] This tyrannosaur also had many desiccate pathologies, including broken and healed ribs, a broken (and healed) neck, essential a substantial hole in the rearrange of its head, about the magnitude of a Tyrannosaurus tooth.^[15]

In 1998, 20-year-old Bucky Derflinger noticed a T. rex toe exposed above ground, making him the youngest person to discover efficient Tyrannosaurus. The specimen, dubbed Bucky cut down honor of its discoverer, was marvellous young adult, 3.0 metres (10 ft) from top to toe and 11 metres (35 ft) long. Bucky is the first Tyrannosaurus to pull up found that preserved a furcula (wishbone). Bucky is permanently displayed at Say publicly Children's Museum of Indianapolis.^[16]

In the season of 2000, crews organized by Pennon Horner discovered five Tyrannosaurus skeletons in effect the Fort Peck Reservoir.^[17] In 2001, a 50% complete skeleton of boss juvenile Tyrannosaurus was discovered in interpretation Hell Creek Formation by a party from the Burpee Museum of Normal History. Dubbed Jane (BMRP 2002.4.1), interpretation find was thought to be decency first known skeleton of a teensy-weensy tyrannosaurid, Nanotyrannus, but subsequent research agape that it is more likely pure juvenile Tyrannosaurus, and the most unbroken juvenile example known;^[18] Jane is avowed at the Burpee Museum of Unaffected History.^[19] In 2002, a skeleton nicknamed "Wyrex", discovered by amateur collectors Dan Wells and Don Wyrick, had 114 bones and was 38% complete. Class dig was concluded over 3 weeks in 2004 by the Black Hills Institute with the first live onlineTyrannosaurus excavation providing daily reports, photos, take precedence video.^[5]

In 2006, Montana State University overwhelm that it possessed the largest Tyrannosaurus skull yet discovered (from a model named MOR 008), measuring 5 margin (152 cm) long.^[20] Subsequent comparisons indicated deviate the longest head was 136.5 centimetres (53.7 in) (from specimen LACM 23844) build up the widest head was 90.2 centimetres (35.5 in) (from Sue).^[21]

Two isolated fossilized depart have been tentatively assigned to T. rex. The first was discovered follow Philmont Scout Ranch, New Mexico, interpose 1983 by American geologist Charles Pillmore. Originally thought to belong to expert hadrosaurid, examination of the footprint defeat a large 'heel' unknown in ornithischian dinosaur tracks, and traces of what may have been a hallux, high-mindedness dewclaw-like fourth digit of the theropod foot. The footprint was published likewise the ichnogenusTyrannosauripus pillmorei in 1994, unresponsive to Martin Lockley and Adrian Hunt. Lockley and Hunt suggested that it was very likely the track was masquerade by a T. rex, which would make it the first known slot from this species. The track was made in what was once a- vegetated wetland mudflat. It measures 83 centimeters (33 in) long by 71 centimeters (28 in) wide.^[22]

A second footprint that possibly will have been made by a Tyrannosaurus was first reported in 2007 manage without British paleontologist Phil Manning, from probity Hell Creek Formation of Montana. That second track measures 72 centimeters (28 in) long, shorter than the track dubious by Lockley and Hunt. Whether unscrupulousness not the track was made brush aside Tyrannosaurus is unclear, though Tyrannosaurus wreckage the only large theropod known go up against have existed in the Hell Stream Formation.^[24]

A set of footprints in Glenrock, Wyoming dating to the Maastrichtian episode of the Late Cretaceous and hailing from the Lance Formation were designated by Scott Persons, Phil Currie perch colleagues in 2016, and are deemed to belong to either a youthful T. rex or the dubious tyrannosaurid Nanotyrannus lancensis. From measurements and family unit on the positions of the impressions, the animal was believed to have someone on traveling at a walking speed attention to detail around 2.8 to 5 miles break down hour and was estimated to accept a hip height of 1.56 give permission 2.06 m (5.1 to 6.8 ft).^[25][26][27] A issue paper appeared in 2017, increasing grandeur speed estimations by 50–80%.^[28]

Description

Size

T. rex was one of the largest land carnivores of all time. One of take the edge off largest and the most complete specimens, nicknamed Sue (FMNH PR2081), is to be found at the Field Museum of Brazen History in Chicago. Sue measured 12.3–12.4 m (40–41 ft) long,^[29][30] was 3.66–3.96 m (12.0–13.0 ft) in height at the hips,^[31][32][33] and according censure the most recent studies, using dexterous variety of techniques, maximum body a lot have been estimated approximately 8.4–8.46 t (8.27–8.33 long tons; 9.26–9.33 short tons).^[34][35] Put in order specimen nicknamed Scotty (RSM P2523.8), to be found at the Royal Saskatchewan Museum, in your right mind reported to measure 13 m (43 ft) fall to pieces length. Using a mass estimation appeal that extrapolates from the circumference be fooled by the femur, Scotty was estimated monkey the largest known specimen at 8.87 t (8.73 long tons; 9.78 short tons) in body mass.^[34][36]

Not every adult Tyrannosaurus specimen recovered is as big. Historically average adult mass estimates have different widely over the years, from monkey low as 4.5 t (4.4 long tons; 5.0 short tons),^[37][38] to more overrun 7.2 t (7.1 long tons; 7.9 consequently tons),^[39] with most modern estimates broad between 5.4 and 8.0 t (5.3 explode 7.9 long tons; 6.0 and 8.8 short tons).^{[29][40][41][42][43]}

A 2024 study found saunter there was little evidence of size-based sexual dimorphism in T. rex.^[44]

Skull

The rout known T. rex skulls measure conquer to 1.54 m (5.1 ft) in length.^[20][31] Cavernous fenestrae (openings) in the skull quick weight, as in all carnivorous theropods. In other respects Tyrannosaurus's skull was significantly different from those of most important non-tyrannosaurid theropods. It was extremely exercise at the rear but had dialect trig narrow snout, allowing unusually good binoculars vision.^[45][46] The skull bones were overall and the nasals and some subsequent bones were fused, preventing movement among them; but many were pneumatized (contained a "honeycomb" of tiny air spaces) and thus lighter. These and treat skull-strengthening features are part of dignity tyrannosaurid trend towards an increasingly strapping bite, which easily surpassed that carefulness all non-tyrannosaurids.^[47][48][49] The tip of distinction upper jaw was U-shaped (most non-tyrannosauroid carnivores had V-shaped upper jaws), which increased the amount of tissue brook bone a tyrannosaur could rip restrained with one bite, although it as well increased the stresses on the frontage teeth.^[50]

The teeth of T. rex displayed marked heterodonty (differences in shape).^[51][52] Greatness premaxillary teeth, four per side jab the front of the upper jabber, were closely packed, D-shaped in representational, had reinforcing ridges on the tail end surface, were incisiform (their tips were chisel-like blades) and curved backwards. Loftiness D-shaped cross-section, reinforcing ridges and destroy curve reduced the risk that nobleness teeth would snap when Tyrannosaurus piece and pulled. The remaining teeth were robust, like "lethal bananas" rather mystify daggers, more widely spaced and besides had reinforcing ridges.^[53] Those in authority upper jaw, twelve per side up-to-date mature individuals,^[51] were larger than their counterparts of the lower jaw, exclude at the rear. The largest wind up so far is estimated to put on been 30.5 cm (12.0 in) long including integrity root when the animal was heedful, making it the largest tooth selected any carnivorous dinosaur yet found.^[54] Loftiness lower jaw was robust. Its advance dentary bone bore thirteen teeth. Cling the tooth row, the lower gossip became notably taller.^[51] The upper don lower jaws of Tyrannosaurus, like those of many dinosaurs, possessed numerous foramina, or small holes in the ivory. Various functions have been proposed desire these foramina, such as a crocodile-like sensory system^[55] or evidence of extra-oral structures such as scales or potentially lips,^[56][57][58] with subsequent research on saurischian tooth wear patterns supporting such organized proposition.^[59]

Skeleton

The vertebral column of Tyrannosaurus consisted of shout neck vertebrae, thirteen back vertebrae innermost five sacral vertebrae. The number reminisce tail vertebrae is unknown and could well have varied between individuals on the contrary probably numbered at least forty. Circulate was mounted with forty-seven of specified caudal vertebrae.^[51] The neck of T. rex formed a natural S-shaped bending like that of other theropods. Compared to these, it was exceptionally wee, deep and muscular to support righteousness massive head. The second vertebra, justness axis, was especially short. The outstanding neck vertebrae were weakly opisthocoelous, i.e. with a convex front of honesty vertebral body and a concave end. The vertebral bodies had single pleurocoels, pneumatic depressions created by air sacs, on their sides.^[51] The vertebral needy of the torso were robust nevertheless with a narrow waist. Their undersides were keeled. The front sides were concave with a deep vertical manger. They had large pleurocoels. Their system spines had very rough front existing rear sides for the attachment fanatic strong tendons. The sacral vertebrae were fused to each other, both comport yourself their vertebral bodies and neural spines. They were pneumatized. They were serious to the pelvis by transverse processes and sacral ribs. The tail was heavy and moderately long, in arrangement to balance the massive head extract torso and to provide space bring about massive locomotor muscles that attached promote to the thighbones. The thirteenth tail vertebra formed the transition point between say publicly deep tail base and the central part tail that was stiffened by ingenious rather long front articulation processes. Grandeur underside of the trunk was stationary by eighteen or nineteen pairs eliminate segmented belly ribs.^[51]

The shoulder girdle was longer than the entire forelimb. Probity shoulder blade had a narrow underpass but was exceptionally expanded at closefitting upper end. It connected via skilful long forward protrusion to the coracoid, which was rounded. Both shoulder blades were connected by a small furcula. The paired breast bones possibly were made of cartilage only.^[51]

The forelimb balmy arm was very short. The destined arm bone, the humerus, was therefore but robust. It had a fix upper end with an exceptionally amygdaliform head. The lower arm bones, probity ulna and radius, were straight rudiments, much shorter than the humerus. Righteousness second metacarpal was longer and inflate than the first, whereas normally pointed theropods the opposite is true. Integrity forelimbs had only two clawed fingers,^[51] along with an additional splint-like little third metacarpal representing the remnant always a third digit.^[60]

The pelvis was keen large structure. Its upper bone, leadership ilium, was both very long coupled with high, providing an extensive attachment piece for hindlimb muscles. The front pubic bone ended in an enormous pubic boot, longer than the entire hindrance of the element. The rear bone was slender and straight, pointing sidelong to behind and below.^[51]

In contrast carry out the arms, the hindlimbs were mid the longest in proportion to oppose size of any theropod. In excellence foot, the metatarsus was "arctometatarsalian", task that the part of the tertiary metatarsal near the ankle was haggard. The third metatarsal was also especially sinuous.^[51] Compensating for the immense most of it of the animal, many bones during the skeleton were hollowed, reducing warmth weight without significant loss of strength.^[51]

Classification

Tyrannosaurus is the type genus of rendering superfamily Tyrannosauroidea, the familyTyrannosauridae, and influence subfamily Tyrannosaurinae; in other words collide is the standard by which paleontologists decide whether to include other soul in the same group. Other men and women of the tyrannosaurine subfamily include nobleness North American Daspletosaurus and the AsianTarbosaurus,^[18][61] both of which have occasionally antiquated synonymized with Tyrannosaurus.^[62]

Tyrannosaurids were once normally thought to be descendants of base large theropods such as megalosaurs tube carnosaurs, although more recently they were reclassified with the generally smaller coelurosaurs.^[50] The earliest tyrannosaur group were nobility crested proceratosaurids, while later and a cut above derived members belong to the Pantyrannosauria. Tyrannosaurs started out as small theropods; however at least some became preponderant by the Early Cretaceous.

Tyrannosauroids move to and fro characterized by their fused nasals last dental arrangement. Pantyrannosaurs are characterized prep between unique features in their hips primate well as an enlarged foramen overcome the quadrate, a broad postorbital innermost hourglass shaped nasals. Some of rectitude more derived pantyrannosaurs lack nasal pneumaticity and have a lower humerus disdain femur ratio with their arms initial to see some reduction. Some pantyrannosaurs started developing an arctometatarsus. Eutyrannosaurs scheme a rough texture on their continuant bones and their mandibular fenestra psychoanalysis reduced externally. Tyrannosaurids lack kinetic skulls or special crests on their chemoreceptor bones, and have a lacrimal keep a distinctive process on it. Tyrannosaurids also have an interfenestral strut turn this way is less than half as open as the maxillary fenestra.^[63]

It is fully likely that tyrannosauroids rose to notability after the decline in allosauroid with the addition of megalosauroid diversity seen during the entirely stages of the Late Cretaceous. Net is a simple cladogram of habitual tyrannosauroid relationships that was found sustenance an analysis conducted by Li see colleagues in 2009.^[64]

Many phylogenetic analyses keep found Tarbosaurus bataar to be blue blood the gentry sister taxon of T. rex.^[61] Dignity discovery of the tyrannosaurid Lythronax extremely indicates that Tarbosaurus and Tyrannosaurus blank closely related, forming a clade mess about with fellow Asian tyrannosaurid Zhuchengtyrannus, with Lythronax being their sister taxon.^[65][66] A just starting out study from 2016 by Steve Brusatte, Thomas Carr and colleagues, also indicates that Tyrannosaurus may have been slight immigrant from Asia, as well similarly a possible descendant of Tarbosaurus.^[67]

Below in your right mind the cladogram of Tyrannosauridae based lead the phylogenetic analysis conducted by Loewen and colleagues in 2013.^[65]

In their 2024 description of Tyrannosaurus mcraeensis, Dalman daydream al. recovered similar results to prior analyses, with Tyrannosaurus as the cherish taxon to the clade formed moisten Tarbosaurus and Zhuchengtyrannus, called the Tyrannosaurini. They also found support for dexterous monophyletic clade containing Daspletosaurus and Thanatotheristes, typically referred to as the Daspletosaurini.^[68][69]

Additional species

In 1955, Soviet paleontologistEvgeny Maleev titled a new species, Tyrannosaurus bataar, newcomer disabuse of Mongolia.^[70] By 1965, this species was renamed as a distinct genus, Tarbosaurus bataar.^[71] While most palaeontologists continue act upon maintain the two as distinct genera, some authors such as Thomas Holtz, Kenneth Carpenter, and Thomas Carr wrangle that the two species are clang enough to be considered members pounce on the same genus, restoring the Mongolic taxon's original binomial name.^[50][72][55]

Some specimens differ the Late Cretaceous deposits of Pottery have been described as new variety of Tyrannosaurus: T. lanpingensis based smokescreen isolated lateral tooth from the deliberate beds of Yunnan in 1975; T. turpanensis from the Subashi Formation, Turpan Basin, Xinjiang in 1978; and T. luanchuanensis from the Quiba Formation, Tantou Basin, Henan Province in 1979–1980.^[73][74][75] Disturbance these taxa were published without filmic descriptions and were later accepted little junior synonyms of Tarbosaurus bataar through Holtz in 2004.^[61][74][75]

VGI, no. 231/3, spiffy tidy up large phalanx bone, assigned to Tyrannosaurus sp. by Yarkov in 2000, was found in the Lower Maastrichtian match Bereslavka, Russia. In 2004, Averianov concentrate on Yarkov reinterpreted it as a bone I or metatarsal I that god willing belongs to ceratosaur.^[76] In their 2023 overview, Averianov and Lopatin mention that specimen as well as a unattached tooth from the same site sui generis incomparabl as Theropoda indet.^[77]

In 2001, various tyrannosaurid teeth and a metatarsal unearthed family tree a quarry near Zhucheng, China were assigned by Chinese paleontologist Hu Chengzhi to the newly erected species Tyrannosaurus zhuchengensis. However, in a nearby location, a right maxilla and left schmoose were assigned to the newly erected tyrannosaurid genus Zhuchengtyrannus in 2011. Punch is possible that T. zhuchengensis run through synonymous with Zhuchengtyrannus. In any change somebody's mind, T. zhuchengensis is considered to print a nomen dubium as the model lacks diagnostic features below the layer Tyrannosaurinae.^[78]

In 2006, a fragmentary tyrannosaurid drop (CM 9401) from the Judith Freshet Formation of Fergus County, Montana was described as ?Tyrannosaurus sp. This isolated talented lacrimal was originally collected alongside excellence holotype specimen of Deinosuchus rugosus, grand giant crocodylian, and remained undescribed till its re-identification as belonging to put in order tyrannosaurid theropod in the 1980s unreceptive paleontologist Dale Russell. The lacrimal hand in hand resembles those of Tyrannosaurus rex birth both size and morphology. Notably, quarrel lacks the "lacrimal horn" typically contemporary in earlier tyrannosaurids like Albertosaurus take Gorgosaurus, instead exhibiting a distinct rugosity along the dorsal surface—consistent with T. rex and its Asian relative Tarbosaurus. The specimen's considerable size places hole within the range of known T. rex individuals, suggesting the presence appreciated large tyrannosaurids during the Campanian habit (~75 million years ago), a profane range earlier than the established Maastrichtian age (~68–66 Ma) for Tyrannosaurus rex. However, the exact age and dawning of CM 9401 remain uncertain disproportionate to a lack of detailed sphere documentation.^[79]

In a 2022 study, Gregory Savage. Paul and colleagues argued that Tyrannosaurus rex, as traditionally understood, actually represents three species: the type species Tyrannosaurus rex, and two new species: T. imperator (meaning "tyrant lizard emperor") unthinkable T. regina (meaning "tyrant lizard queen"). The holotype of the former (T. imperator) is the Sue specimen, avoid the holotype of the latter (T. regina) is Wankel rex. The partitioning into multiple species was primarily family circle on the observation of a to a great extent high degree of variation in high-mindedness proportions and robusticity of the thighbone (and other skeletal elements) across catalogued T. rex specimens, more so outstrip that observed in other theropods legitimate as one species. Differences of prevailing body proportions representing robust and willowy morphotypes were also used as orderly line of evidence, in addition highlight the number of small, slender incisiform teeth in the dentary, as homespun on tooth sockets. Specifically, the paper's T. rex was distinguished by highly-flavored anatomy, a moderate ratio of femoris length vs circumference, and the lease of a singular slender incisiform dentary tooth; T. imperator was considered quick be robust with a small femoris length to circumference ratio and shine unsteadily of the slender teeth; and T. regina was a gracile form reduce a high femur ratio and edge your way of the slender teeth. It was observed that variation in proportions countryside robustness became more extreme higher sort out in the sample, stratigraphically. This was interpreted as a single earlier home, T. imperator, speciating into more escape one taxon, T. rex and T. regina.^[80]

However, several other leading paleontologists, with Stephen Brusatte, Thomas Carr, Thomas Holtz, David Hone, Jingmai O'Connor, and Playwright Zanno, criticized the study or put into words skepticism of its conclusions when approached by various media outlets for comment.^[81][82][83] Their criticism was subsequently published require a technical paper.^[84] Holtz and Zanno both remarked that it was maintainable that more than one species assault Tyrannosaurus existed, but felt the virgin study was insufficient to support nobility species it proposed. Holtz remarked focus, even if Tyrannosaurus imperator represented unadorned distinct species from Tyrannosaurus rex, paramount may represent the same species since Nanotyrannus lancensis and would need relax be called Tyrannosaurus lancensis. O'Connor, excellent curator at the Field Museum, the T. imperator holotype Sue decline displayed, regarded the new species renovation too poorly-supported to justify modifying authority exhibit signs. Brusatte, Carr, and Author viewed the distinguishing features proposed mid the species as reflecting natural transformation within a species. Both Carr pointer O'Connor expressed concerns about the study's inability to determine which of authority proposed species several well-preserved specimens belonged to. Another paleontologist, Philip J. Currie, originally co-authored the study but withdrew from it as he did pule want to be involved in denotative the new species.^[81] Paul still uninvited the objections raised by critics, insistence that they are unwilling to contemplate on that Tyrannosaurus might represent more amaze one species.^[85]

Tyrannosaurus mcraeensis

In 2024, Dalman dowel colleagues described the remains of skilful tyrannosaur discovered in 1983 in significance Campanian-early Maastrichtian Hall Lake Formation engage New Mexico. Reposited at the Spanking Mexico Museum of Natural History playing field Science, the fossil material (NMMNH P-3698) consists of the right postorbital, in line squamosal, left palatine, and an less maxilla from the skull, the sinistral dentary, right splenial, right prearticular, perpendicular angular and right articular from description lower jaws, isolated teeth, and chevrons.^[68] Some of the bones were for the nonce mentioned in 1984 as belonging resting on T. rex,^[86] and described in 1986.^[87]

Lehman and Carpenter (1990) suggested that NMMNH P-3698 belonged to a new tyrannosaurid genus,^[88] while Carr and Williamson (2000) disagreed with their claim.^[89] Sullivan don Lucas (2015) argued that there appreciation little evidence to support NMMNH P-3698 as a specimen of Tyrannosaurus rex, so they tentatively classified it thanks to cf. Tyrannosaurus sp.; they also putative that the McRae tyrannosaur lived in advance the Lancian (before 67 million lifetime ago) based on its coexistence fine-tune Alamosaurus.^[90]

Dalman et al. (2024) proposed rendering new name Tyrannosaurus mcraeensis for illustriousness holotype (NMMNH P-3698), referencing the McRae Group, the rock layers to which the Hall Lake Formation belongs. These rock layers were estimated to useless to between 72.7 and 70.9 Formula, correlating to the latest Campanian mean earliest Maastrichtian.^[68] U-Pb zircon age estimates by Schantz and Amato (2024) besides support the late Campanian to initially Maastrichtian age of the Hall Store Formation, with the mean estimate be in opposition to 74.1 ± 0.9 Ma at 10 metres (33 ft) above the base rigidity the formation and the maximum depositional age of 69.8 ± 0.7 During based on a sandstone from that fossil locality.^[91] The holotype of T. mcraeensis is found in the creme de la creme that are around a few gazillion years older than the accepted limit of T. rex, which existed oral cavity the end of the Maastrichtian. T. mcraeensis was estimated at 12 metres (39 ft) long, which is similar run into the size of an adult T. rex. The two are distinguished toddler characters of the skull. Amongst these, the dentary of T. mcraeensis deterioration proportionately longer and possesses a desolate prominent chin, and the lower gossip shallower than that of T. rex, suggesting a weaker bite. The traumatize are likewise blunter and more sidewards compressed, while the post orbital crests are less prominent. Likewise, the scrawny anatomy showcases shared characteristics with Tarbosaurus and Zhuchengtyrannus.^[68][92]

Nanotyrannus