Tyrannosaurus rex
Tyrannosaurus rex (from Latinized Greek tyrannus 'tyrant' and saurus &# 39;lizard', and Latin rex, 'king') is the only known species of the fossil genus Tyrannosaurus from the tyrannosaurid theropod dinosaur, which lived in the late Cretaceous period, approximately 68 to 66 million years ago, in the Maastrichtian, in present-day North America. Its distribution on the continent was much wider than that of other tyrannosaurids; He is a common figure in popular culture. It was one of the last non-avian dinosaurs to exist before the Cretaceous-Tertiary mass extinction. It is also known as t-rex and in Spanish as tyrannosaurus rex or simply tyrannosaurus.
Like other tyrannosaurids, T. rex was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to its long and powerful hindlimbs, Tyrannosaurus's upper limbs were small, but surprisingly strong for their size, ending in two clawed fingers. Although other theropods rival or exceed Tyrannosaurus rex in size, it is still the largest known tyrannosaurid and one of the largest known predators on Earth, measuring twelve to thirteen meters long, four meters tall up to the hips, and with estimated weights between six and nine tons. For a long time it was the largest carnivore in its ecosystem; it must have been the top predator, hunting hadrosaurids and ceratopsids, although some experts have suggested that it was primarily a scavenger. The debate of whether Tyrannosaurus was a dominant predator or a scavenger is one of the longest in paleontology.
There are more than 30 identified Tyrannosaurus rex specimens, some of which are nearly complete skeletons. Connective tissue and proteins have been found in at least one of these specimens. The abundance of fossil material has allowed many aspects of their biology to be investigated in detail, including their life cycle and biomechanics. The feeding habits, physiology, and potential speed of Tyrannosaurus rex are controversial. Its taxonomy is also controversial, with some scientists considering Tarbosaurus bataar of Asia as a second species of Tyrannosaurus while others maintain Tarbosaurus as a genus. separate. Several other genera of North American tyrannosaurids have also been synonymized with Tyrannosaurus.
Description
Tyrannosaurus rex had the basic body plan of members of its family: large head, short S-shaped neck, torso parallel to the ground with small forelimbs, highly developed hind limbs and a long tail. Different found specimens of Tyrannosaurus rex measured between 11.1 and 13 meters in length, with estimated weights of 5.6 to 9.5 tons. Tyrannosaurus It had a large 1.4 m skull provided with ocular and nasal fenestrae. Its skull presents a large number of fused bones, supplying mobility with a more massive structure, an unusual fact in theropods, which generally had light bones. The neck was thick, muscular and short.
The neck of Tyrannosaurus rex formed a natural S-shaped curve like other theropods, but it was short and muscular to support its huge head. The upper limbs had only two clawed fingers, along with an additional small metacarpal, a vestige of a third digit. In contrast, the hind limbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, made up of more than forty vertebrae, to balance the enormous torso and head. To compensate for the animal's immense size, many bones in its skeleton were hollow, reducing its weight without significant loss of strength.
Size
The largest quasi-complete specimen, FMNH PR2081, nicknamed Sue, measured between 12.3 and 12.4 meters long, and 3.66 to 3, 96 tall to the hips. Estimates of its total mass have varied over the years, from a recent high of 8.4 tons, to a low of 4.5, with other estimates of between 5.4 and 7.2 tons. A specimen nicknamed Scotty, RSM P2523.8, located at the Royal Saskatchewan Museum, is reported to measure 13 m long. Using a mass estimation technique that extrapolates from the circumference of the femur, Scotty was estimated to be the largest known specimen, at 8.87 metric tons of body mass.
Other studies have given estimates of 9.5, 8.4, and 7.4 tons of mass. These last estimates were obtained both with the finely calibrated reconstruction of volumetric models of the body, which take into account modern data on its osteology, as well as with the air sacs and new interpretations of its muscle mass, and in the regression equations based on the circumference of the bones that support the body. Not all recovered adult Tyrannosaurus specimens are this large. Historically, average adult mass estimates have varied widely over the years, from as low as 4.5 metric tons, to over 7.2 metric tons, with most modern estimates. ranging from 5.4 tons to 8.0 tons. Although it was larger than the Jurassic theropod Allosaurus and rivaled in size African Carcharodontosaurus, according to estimates, Tyrannosaurus was relatively smaller than other Cretaceous theropods such as Spinosaurus and Giganotosaurus.
Skull
The largest known Tyrannosaurus rex skull is 1.52 meters long. Large openings, called fenestrae, reduced weight and provided places for muscle attachment, as seen in all carnivorous theropods. But in other respects the Tyrannosaurus skull is significantly different from that of large non-tyrannosaurid theropods. It is extremely wide at the back but has a narrow snout, allowing unusually good binocular vision. The skull bones were massive, and the nasal and some other bones were fused together, allowing no movement between them, although many were pneumatized, containing a "honeycomb" of tiny air spaces that may have made the bones more flexible as well as lighter. These and other features of cranial consolidation are part of the tyrannosaurid tendency toward ever greater bite, which easily surpassed that of all non-tyrannosaurids. The end of the upper jaw was U-shaped. , whereas in most non-tyrannosaurid carnivores the upper jaws were V shaped, increasing the amount of tissue and bone a tyrannosaur could bite off, but also increased stresses on the front teeth.
The lower jaw was robust. Its frontal dental bone had thirteen teeth. Behind the row of teeth, the lower jaw became noticeably taller. The upper and lower jaws of Tyrannosaurus, like those of many dinosaurs, possessed numerous foramina, or small holes in the bone. Various functions have been proposed for these foramina, such as a crocodile-like sensory system or evidence for extraoral structures such as scales or potentially lips.
Teeth
The teeth of Tyrannosaurus rex show marked heterodonty (differently shaped teeth). The premaxillary teeth, at the front of the upper jaw, the maxilla, were close together, with a cross section D-shaped, had reinforced ridges on the posterior edge, were incisiform, like chisel-sharp cusps, and curved backwards. These features reduced the risk of teeth breaking when Tyrannosaurus bit and tore. The rest of the teeth were stout, more like "sharp bananas" than daggers; they were further spaced apart and were also reinforced at the edges. Those on the upper jaw were larger than those on the rear of the lower jaw. The largest Tyrannosaurus tooth found so far is estimated to have been 30.5 centimeters long, including the root, making this tooth the largest of any carnivorous dinosaur discovered to date.
Axial skeleton
The vertebral column of Tyrannosaurus consisted of ten neck vertebrae, thirteen back vertebrae, and five sacral vertebrae. The number of tail vertebrae is unknown and may well have varied between individuals, but there were probably at least 40. Sue was mounted with 47 of those caudal vertebrae. The neck of T. rex formed a naturally curved S shape like other theropods. Compared to these, it was exceptionally short, deep, and muscular to support its massive head. The second vertebra, the axis, was especially short. The remaining neck vertebrae were weakly opisthocoelose, that is, with a convex front of the vertebral body and a concave rear. The vertebral bodies had individual pleurocoelli, pneumatic depressions created by air sacs, on their sides. The vertebral bodies of the torso were stocky but narrow-waisted. Their underparts were keeled. The front sides were concave with a deep vertical channel. They had large pleurocoels. Its neural spines had very rough front and back sides for the attachment of strong tendons. The sacral vertebrae were fused together, both in their vertebral bodies and in their neural spines. They were pneumatic. They were connected to the pelvis by transverse processes and sacral ribs. The tail was heavy and moderately long, to balance the massive head and torso, and to provide space for the huge locomotor muscles attached to the femora. The thirteenth tail vertebra formed the transition point between the base of the deep tail and the middle tail which was stiffened by a rather long frontal articulation process. The lower part of the trunk was covered by eighteen or nineteen pairs of segmented abdominal ribs.
Upper limbs
The shoulder girdle was longer than the entire forelimb. The shoulder blade had a narrow shaft but was unusually expanded at its upper end. It connected through a long bulge forward with the coracoid, which was rounded. Both shoulder blades were connected by a small furcula. The paired sterna were possibly made only of cartilage. The upper limb, or arm, was very short. The upper arm bone, the humerus, was short but stout. It had a narrow top end with an exceptionally rounded head. The forearm bones, the ulna and radius, were straight elements, much shorter than the humerus. The second metacarpal was longer and wider than the first, while the opposite is usually the case in theropods. The forelimbs had only two clawed fingers, along with an additional small splint-like third metacarpal representing the remnant of a third finger.
Lower limbs
The pelvis was a large structure. Its top bone, the ilium, was very long and high, providing a large attachment area for the muscles of the hind legs. The frontal pubic bone ended in a huge pubic boot, longer than the entire axis of the element. The posterior ischium was thin and straight, pointing obliquely backwards and downwards.
In contrast to the arms, the hind legs were among the longest in proportion to body size of any theropod. In the foot, the metatarsal was 'arctometatarsal', meaning that the part of the third metatarsal near the ankle was impinged. The third metatarsal was also exceptionally sinuous. To compensate for the animal's immense bulk, many bones throughout the skeleton were hollowed out, reducing its weight without significant loss in strength.
Discovery and research
As of 2006, 30 specimens had been found, including only three complete skulls. The first specimens found played an important role in the so-called War of the Bones. Tyrannosaurus rex is the best known carnivorous dinosaur in human popular culture.
First discoveries
All specimens have been found in North America. Some teeth that today are documented as Tyrannosaurus rex were found in 1874 by Arthur Lakes near Golden, Colorado. In the early 1890s, John Bell Hatcher collected postcranial elements in eastern Wyoming. These fossils were originally considered to belong to a giant species of Ornithomimus, O. grandis, later called Deinodon, but now considered a specimen of Tyrannosaurus rex.
Manospondylus
In 1892, Edward Drinker Cope found two vertebral fragments, one of which is missing, from a large dinosaur. Cope believed the fragments belonged to an "agathaumid" dinosaur, ceratopsid, and named them Manospondylus gigas, meaning "giant porous vertebra", in reference to the numerous openings for blood vessels found in the bone. The remains of M. gigas were, in 1907, identified by Hatcher as those of a theropod rather than a ceratopsid. It was attributed to Tyrannosaurus rex in 1912 by Henry Fairfield Osborn. Henry Fairfield Osborn recognized the similarity between Manospondylus gigas and T. rex as early as 1917, by which time the second vertebra had been lost. Due to the fragmented state of the vertebrae of Manospondylus, Osborn did not synonymize the two genera, instead considering the older genus indeterminate.
In June 2000, a team from the Black Hills Institute located the location of M. gigas in South Dakota and unearthed new bones of about 10% of a Tyrannosaurus skeleton at that location, cataloged under the number BHI 6248. Investigators concluded that it was the same individual and that the remains were identical to those of Tyrannosaurus rex. According to the rules of the International Code of Zoological Nomenclature (ICZN), the system that governs the scientific names of animals, Manospondylus gigas should have had priority over Tyrannosaurus rex for have been used first. However, the fourth edition of the ICZN, which came into effect on January 1, 2000, established an exception that allows Tyrannosaurus rex to continue to be considered the valid name. If someone were to challenge it before the ICZN, which has not yet happened, it would most likely be considered a nomen protectum, "protected name", and Manospondylus gigas would be considered nomen oblitum, "forgotten name".
Henry Fairfield Osborn, president of the American Museum of Natural History, described Tyrannosaurus rex to science in 1905. The generic name comes from the Greek words τυραννος, tyrannos, meaning "tyrant" and σαυρος, sauros, for "lizard". Osborn used the Latin word rex, which translates as "king", for the specific term. The full binomial nomenclature for this species, Tyrannosaurus rex, translates from Latin as "the king of tyrant lizards", emphasizing the large size of the dinosaur, with which, It is supposed that it dominated all the other animals of its time.
Work of Barnum Brown, 1900-1940
Barnum Brown, the assistant curator at the American Museum of Natural History, found the second skeleton of T. rex in Wyoming in 1900. He then found another partial skeleton in the Hell Creek Formation in Montana in 1902, comprising approximately 34 fossilized bones. Writing at the time, Brown said: "Quarry No. 1 contains the femur, pubis, humerus, three vertebrae and two indeterminate bones of a large carnivorous dinosaur not described by Marsh...I have never seen anything like it in the Cretaceous". The first specimen was originally named Dynamosaurus imperiosus in the same document in which Tyrannosaurus rex was described from the second onwards. In 1906, Osborn recognized that the two skeletons were of the same species and selected Tyrannosaurus as the preferred name. Had it not been for the page order, Dynamosaurus would have become the official name. The original material for Dynamosaurus is in the collections of the Natural History Museum, London. In 1941, the type specimen T. rex was sold to the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, for $7,000. Dynamosaurus, would later be honored for the 2018 description of another tyrannosaurid species by Andrew McDonald and his colleagues, Dynamoterror dynastes, whose name was chosen in reference to the 1905 name, as it had been a "childhood favourite" from McDonald's.
In all, Barnum Brown found five partial skeletons of T. rex. Brown collected the second tyrannosaur from him in 1902 and 1905 from the Hell Creek Formation, Montana. This was the holotype that Osborn used to describe Tyrannosaurus rex in 1905. In 1941 he sold it to the Carnegie Museum of Natural History in Pittsburgh (Pennsylvania). Brown's fourth and most important find, also discovered in the Hell Creek formation, is on display at the American Museum of Natural History in New York. From the 1910s to the late 1950s, discoveries of Barnum's remained the only Tyrannosaurus specimens, as the Great Depression and wars kept many paleontologists out of the field.
Resurgence of Interest, 1940-1990
Beginning in the 1960s there was renewed interest in Tyrannosaurus, resulting in the recovery of 42 skeletons in western North America, between 5 and 80% complete according to the bone count. In 1967, Dr. William MacMannis located and recovered the skeleton named MOR 008, which is 15% complete by bone count and has a reconstructed skull on display at the Museum of the Mountains. rocky. The 1990s saw numerous discoveries, with nearly twice as many finds as in all previous years, including two of the most complete skeletons found to date, Sue and Stan.
Several other Tyrannosaurus rex skeletons were discovered until the late 1980s. The skull of Nanotyrannus, often considered a T. rex juvenile, was recovered from Montana in 1942. In 1966, workers at the American Museum of Natural History under the direction of Harley Garbani discovered a complete skull of T. rex mature, LACM 23844. When it was shown in Los Angeles, LACM 23844 became the largest exposed skull of T. rex worldwide. Garbani continued to discover many skeletons for more than a decade, including LACM 23845, the holotype of Albertosaurus megagracilis, many of which are held in the collection of the Museum of Paleontology of the University of California at Berkeley, California. Other skulls and partial skeletons were discovered in South Dakota and Alberta, Canada in the early 1980s.
Until 1987, Tyrannosaurus rex remains were sparse. However, the 1980s–1990s have seen the discovery and description of about a dozen additional specimens. The first was a Tyrannosaurus nicknamed Stan after amateur paleontologist Stan Sacrison, found in the Hell Creek Formation near Buffalo, South Dakota, in the spring of 1987. After 30,000 hours of excavation and preparation, a 65% complete skeleton emerged and is now on display at the Black Hills Museum of Natural History in Hill City, South Dakota. This Tyrannosaurus, whose inventory name is BHI 3033, has many pathologies in its bones, including broken ribs and neck that later healed and a spectacular hole in the back of its its head, the size of a Tyrannosaurus tooth.
Susan Hendrickson, an amateur paleontologist, discovered the fossil skeleton of T. rex, more than 85% complete and largest known to date, in the Hell Creek Formation near Faith, South Dakota, on August 12, 1990. The specimen was nicknamed Sue in honor of its discoverer. On the ownership of that specimen of T. rex an acrimonious legal battle ensued. In 1997 it was resolved in favor of Maurice Williams, the original owner of the land where it was found, and the fossil collection was sold at auction for $7.6 million. As of January 2021, the skeleton has been reassembled and is on display at the Field Museum of Natural History in Chicago. Study of the fossilized bones of Sue show that the individual reached full size at 19 years of age and died 9 years later, living a total of 28 years. Two other fossils of Sue have been discovered. i>T. rex in the same quarry where Sue, a subadult and a juvenile, were found, indicating that T. rex may have lived in packs or other kinds of groups. Early speculation that Sue may have died from a bite to the back of the head has not been confirmed. Many subsequent studies have shown many pathologies, but no bite marks have been found. The damage to the back of the skull may have been caused by postmortem crushing. Some speculation indicates that Sue may have starved to death after contracting a parasitic infection from eating rotten meat. The resulting parasitism would have caused inflammation in the throat, ultimately preventing Sue from being able to eat. This hypothesis is supported by the fine, smooth holes in its skull, which are similar to those caused in modern birds contracting the same type of parasite.
Latest Findings
In 1998, Bucky Derflinger discovered a toe of T. rex exposed above ground, making Derflinger, who was 20 years old at the time, the youngest person to discover a Tyrannosaurus. The specimen, nicknamed Bucky after its discoverer, was a young adult, 3 meters tall and 11 meters long. Bucky is the first Tyrannosaurus found to have a furcula. It is currently on permanent display at the Children's Museum of Indianapolis.
In the summer of 2000, Jack Horner discovered five Tyrannosaurus specimens near the Fort Peck Reservation in Montana. One of these skeletons, nicknamed C. rex, was reported to be the largest Tyrannosaurus ever found.
In 2001, a team of researchers from the Burpee Museum of Natural History in Rockford (Illinois) discovered 50% of the skeleton of a juvenile tyrannosaur, nicknamed Jane, in the Hell Creek Formation in Montana. Initially, the find was considered the first known skeleton of the small tyrannosaurid Nanotyrannus,, but further investigation revealed that the fossil belonged to a juvenile Tyrannosaurus. This specimen is the most complete and best preserved juvenile specimen found to date. Jane has been examined by Jack Horner, Peter Larson, Robert Bakker, Gregorio Erikson, and several other renowned paleontologists for the unique circumstance of the specimen's age at the time of death. In 2021 Jane was on display at the Burpee Museum of Natural History in Rockford, Illinois. In 2002, a skeleton named Wyrex, discovered by amateur collectors Dan Wells and Don Wyrick, had 114 bones and was 38% complete. The dig was concluded over three weeks in 2004 by the Black Hills Institute with the first live Tyrannosaurus dig online providing daily reports, photos and videos.
In 2005 it was announced the recovery of soft tissue from the medullary cavity of a fossilized leg bone of a T. rex, dating to approximately 68 million years ago. The bone had been broken intentionally but reluctantly for shipping and was not preserved in the usual way because its discoverer was keen to investigate the soft tissue. Designated the Museum of the Rockies Specimen MOR 1125, the dinosaur had previously been unearthed in the Hell Creek Formation. Flexible and bifurcated blood vessels and the tissue of the fibrous but elastic bone matrix could be recognized. In addition, blood cell-like microstructures were found within the matrix and blood vessels. The structures are similar to the cells and blood vessels of today's ostrich. However, since this material appears to have been preserved by an unknown process other than normal fossilization, researchers are careful not to claim that this is original material from the dinosaur.
A scientific team has claimed that what was actually found inside the Tyrannosaurus bone was not original tissue but a sticky biofilm created by bacteria that covered the gaps originally occupied by blood vessels and cells. However, there is no evidence that a biofilm can produce branches and hollow tubes like those observed in this case.
If it turned out to be the original material, any surviving proteins could be used to indirectly estimate some of the DNA, deoxyribonucleic acid, contents of the dinosaurs involved, because each protein is typically created by a specific gene. The absence of earlier finds may merely be a consequence of paleontologists assuming tissue preservation was impossible, and simply not looking at it. Since this find, two other tyrannosaurs and one hadrosaur have been found to have these types of structures and soft tissues. Research on some of the tissues involved has suggested that birds are closer to tyrannosaurs on the evolutionary tree than to them. other modern animals.
In 2006 Montana State University revealed that it was in possession of the largest Tyrannosaurus skull yet found. Discovered in the 1960s, MOR-008, recently reconstructed, the skull is 149.9 centimeters long; compared to Sue's skull, 140.7 centimeters, is 6.5% larger.
On April 16, 2021, a UC Berkeley study estimated that the total number of T. rex that inhabited the planet was around 2,500 million, spread over 127,000 generations.
Other species
In 1955 Soviet paleontologist Evgeny Maleev named Tyrannosaurus bataar as a new species from Mongolia. In 1965 this species was renamed Tarbosaurus bataar. Despite the change By name, Tarbosaurus from Mongolia is sometimes classified within the genus Tyrannosaurus as T. bataar, although most tyrannosaur specialists, such as Tom Holtz, see enough differences between the two species to ensure that they are separate genera, while others consider it the Asian species of Tyrannosaurus. A recent description of the skull of Tarbosaurus bataar has shown that it is narrower than that of Tyrannosaurus rex and that during the bite, the distribution The stresses in the skull bones were very different, being closer to that of Alioramus, another Asian tyrannosaurid. A recent cladistic analysis found that Alioramus, and not Tyrannosaurus, is the sister taxon of Tarbosaurus, suggesting that Tarbosaurus and Tyrannosaurus should remain separate.
Other tyrannosaurid fossils found in the same formations as Tyrannosaurus rex have originally been attributed to different taxa, such as Aublysodon and Albertosaurus megagracilis, which was later named Dinotyrannus megagracilis in 1995. However, today these fossils are universally considered to be juvenile specimens of Tyrannosaurus rex.
In 2001, several tyrannosaurus teeth and a metatarsal unearthed in a quarry near Zhucheng, China, were assigned by Chinese paleontologist Hu Chengzhi to the newly erected species Tyrannosaurus zhuchengensis. However, at a nearby site, a right maxilla and left mandible were assigned in 2011 to the newly erected tyrannosaurid genus Zhuchengtyrannus. It is possible that T. zhuchengensis is synonymous with Zhuchengtyrannus. In any case, it is considered that T. zhuchengensis is a nomen dubium, as the holotype lacks diagnostic features below the Tyrannosaurinae level.
Nanotyranus
Tyrannosaurid fossils found in the same formations as T. rex were originally classified as separate taxa, including Aublysodon and Albertosaurus megagracilis, the latter being named Dinotyrannus megagracilis in 1995. These fossils are now universally regarded as belonging to juvenile Tyrannosaurus rex. A small but highly complete skull found in Montana, 60 centimeters long, may be an exception. This skull, CMNH 7541, was originally classified as a species of Gorgosaurus, G. lancensis, by Charles W. Gilmore in 1946, In 1988, the specimen was redescribed by Robert T. Bakker, Phil Currie, and Michael Williams, then curator of paleontology at the Cleveland Museum of Natural History, where it was housed. the original specimen and is now on display. His initial investigation indicated that the skull bones were fused and that it therefore represented an adult specimen. In light of this, Bakker and his colleagues assigned the skull to a new genus called Nanotyrannus, meaning "dwarf tyrant," because of its apparently small adult size. The specimen is estimated to have been around 5.2 meters long when it died. However, in 1999, detailed analysis by Thomas Carr revealed the specimen to be a juvenile, leading Carr and many other paleontologists to consider it a juvenile individual of T. rex. Opinions on the validity of N. lancensis are divided. Many paleontologists consider the skull to be from a juvenile Tyrannosaurus rex. There are minor differences between the two, including a greater number of teeth in N. lancensis, which has led scientists to recommend that the two genera be kept separate, until new discoveries help clarify these issues.
In 2001, a more complete juvenile Tyrannosaurus was discovered, nicknamed Jane, catalog number BMRP 2002.4.1, belonging to the same species than the original Nanotyrannus specimen. This discovery sparked a tyrannosaur conference focusing on validity issues for Nanotyrannus at the Burpee Museum of Natural History in 2005. Several paleontologists who had previously published opinions that N. lancensis was a valid species, including Currie and Williams, saw Jane's discovery as confirmation that Nanotyrannus was, in fact, a T. rex juvenile. Peter Larson continued to support the hypothesis that N. lancensis was a separate but closely related species based on cranial features such as two more teeth in both jaws than T. rex, as well as proportionally larger hands with phalanges on the third metacarpal and different wishbone anatomy in an undescribed specimen. He also argued that Stygivenator, generally considered a juvenile T. rex, may be a specimen of younger Nanotyrannus. Further research revealed that other tyrannosaurids such as Gorgosaurus also experienced a reduction in the number of teeth during growth, and given the disparity in tooth counts between individuals of the same age group in this genus and Tyrannosaurus, this feature may also be due to individual variation. In 2013, Carr noted that all differences claimed to support Nanotyrannus turned out to be individual or ontogenetically variable features or distortion products of the bones..
In 2016, analysis of limb proportions by Persons and Currie suggested that Nanotyrannus specimens had different levels of cursoriality, which could separate it from T. rex. However, paleontologist Manabu Sakomoto has commented that this conclusion may be affected by the low sample size and the discrepancy does not necessarily reflect a taxonomic distinction. In 2016, Joshua Schmerge defended the validity of Nanotyrannus based on features of the skull, including a dental groove in the skull of BMRP 2002.4.1. According to Schmerge, because that feature is absent in T. rex and is only found in Dryptosaurus and Albertosaurinae, this suggests that Nanotyrannus is a distinct taxon within the Albertosaurinae. The same year, Carr and colleagues noted that this was not sufficient to clarify the validity or classification of Nanotyrannus, being a common and ontogenetically variable feature among tyrannosauroids.
A 2020 study by Holly Woodward and colleagues showed that specimens referred to Nanotyrannus were all ontogenetically immature and found it likely that these specimens belonged to T. rex. The same year, Carr published a paper on T. rex. The growth history of CMNH 7541 conforms to the expected ontogenetic variation of the taxon and displays juvenile characteristics found in other specimens. He was classified as a juvenile, under thirteen years of age with a skull of less than 80 centimeters. No significant sexual or phylogenetic variation was noted among any of the 44 specimens studied, and Carr stated that characters of potential phylogenetic importance decline with age as growth occurs. Discussing the paper's results, Carr described how all Nanotyrannus specimens formed a continuous growth transition between smaller juveniles and subadults, unlike what would be expected if it were a separate taxon where specimens would cluster to exclusion. of Tyrannosaurus. Carr concluded that "the 'nanomorphs' they are not so similar to each other and instead form an important bridge in the growth series of T. rex which captures the beginnings of the deep change from the superficial skull of juveniles to the deep skull that is seen in fully developed adults".
T. rex, T. regina and T. imperator
In a 2022 study, Gregory S. Paul and colleagues argued that Tyrannosaurus rex, as traditionally understood, actually represents three species: the type species Tyrannosaurus rex and two new species, Tyrannosaurus imperator, meaning "emperor tyrant lizard " and Tyrannosaurus regina, meaning "queen of tyrant lizards". The holotype of T. imperator is the specimen of Sue, and the holotype of T. regina is Wankel rex. The division into multiple species was based primarily on the observation of a very high degree of variation in the proportions and robustness of the femur and other skeletal elements in specimens of T. rex cataloged, more than observed in other theropods recognized as a single species. Differences in general body proportions representing stout and gracile morphotypes were also used as a line of evidence, in addition to the number of small and slender incisor teeth in the dentary, based on dental alveoli. Specifically, the T. rex in the article was distinguished by its robust anatomy, a moderate ratio of femur length to circumference, and possession of a singular, slender incisiform dentary tooth. It was considered that T. imperator was stout with a small femur length to circumference ratio and two of the teeth slender. T. regina was a graceful form with a high femur ratio and one of the slender teeth. Variation in proportions and robustness were observed to become more extreme higher up in the sample, stratigraphically. This was interpreted as a single previous population, T. imperator, which was speciated in more than one taxon, T. rex and T. Regina.
However, several other prominent paleontologists, including Stephen Brusatte, Thomas Carr, Thomas Holtz, David Hone, Jingmai O'Connor, and Lindsay Zanno, criticized the study or expressed skepticism about its conclusions when approached by various media outlets. for comment. Their critique was later published in a whitepaper. Holtz and Zanno commented that it was plausible that more than one species of Tyrannosaurus existed, but felt the new study was insufficient to support the species he proposed. Holtz commented that even if Tyrannosaurus imperator represented a different species from Tyrannosaurus rex, it may represent the same species as Nanotyrannus lancensis and should be named Tyrannosaurus lancensis. O'Connor, curator of the Field Museum, where the Sue holotype of T. imperator, considered the new species too poorly supported to justify modifying the display posters. Brusatte, Carr, and O'Connor viewed proposed distinguishing features between species as a reflection of natural variation within a species. Both Carr and O'Connor expressed concern about the study's inability to determine to which of the proposed species several well-preserved specimens belonged. Another paleontologist, Philip J. Currie, originally co-authored the study, but withdrew because he did not want to be involved in naming the new species.
In a later article, Paul stood by the conclusion that "Tyrannosaurus" consists of three species. He noted that criticism of the study he names T. imperator and T. regina only focused on two of the characteristics used to distinguish the two new species, the number of small incisor teeth and the robustness of the femur, whereas the original study also compared the robustness of other bones, the maxilla, the dentary, humerus, ilium and metatarsals. Furthermore, Paul argued that the "Tyrannosaurus" it can be separated into three different species based on the shape of the horny bumps, 'postorbital bumps', behind the eyes. Paul also argued that previous research that concluded that Tyrannosaurus only consists of one species, T. rex, simply assumed that all Tyrannosaurus skeletons are a single species, and that many new dinosaur species have been named on the basis of fewer differences than he and his colleagues used. by proposing T. imperator and T. regina. If Tyrannosaurus is treated like any other dinosaur, it should be separated into different species.
List of misassigned species
A large number of invalid species of Tyrannosaurus have been reclassified as T. rex, as well as Tarbosaurus. The list is as follows:
- T. amplus (Marsh, 1892) nomen dubium (originally Aublysodon) species not valid, now Aublysodon amplus.
- T. bataar (Maleev, 1955) invalid species, now Tarbosaurus bataar.
- T. efremovi (Maleev, 1955) (originally Tarbosaurus) species not valid, now Tarbosaurus efremovi.
- T. gigantus (1990) nomen nudum, not valid species, now Tyrannosaurus rex.
- T. empiresus (Osborn, 1905) (originally Dynamosaurus) species not valid, now Tyrannosaurus rex.
- T. lancensis (Gilmore, 1946) Gorgosaurus) = Tyrannosaurus rex?
- T. lancinator (Maleev, 1955) (originally Gorgosaurus) species not valid, now Tarbosaurus bataar.
- T. lanpingensis (Yeh, 1975) nomen dubium species not valid, now Tarbosaurus lanpingensis.
- T. luanchuanensis (Dong, 1979) nomen dubium species not valid, now Tarbosaurus luanchuansis.
- T. megagracilis (Paul, 1988) (originally Albertosaurus) = Tyrannosaurus rex?
- T. novojilovi (Maleev, 1955) (originally Gorgosaurus) = Tarbosaurus bataar?
- T. stanwinstonorum (Pickering, 1995) nomen nudum species invalid, now Tyrannosaurus rex.
- T. torosus (D. A. Russell, 1970) Daspletosaurus) species not valid, now Daspletosaurus torosus.
- T. turpanensis (Zhai, Zheng & Tong, 1978) invalid species, now Tarbosaurus bataar.
Classification
Tyrannosaurus is the worldwide accepted type genus of the superfamily Tyrannosauroidea, the family Tyrannosauridae, and the subfamily Tyrannosaurinae i>. The subfamily Tyrannosaurinae includes Daspletosaurus from North America and Tarbosaurus from Asia; which are occasionally classified within the genus Tyrannosaurus. Tyrannosaurids were long considered to be the descendants of earlier large theropods such as megalosaurids and carnosaurs but in 2021 they are placed among the generally smaller coelurosaurs. Tyrannosauridae to include a complete list of advanced tyrannosaurs, such as Gorgosaurus, Albertosaurus, and Alectrosaurus of the more general Tyrannosauroidea which includes primitive tyrannosaurs such as Dilong, Guanlong and Eotyrannus.
Many phylogenetic analyzes have found Tarbosaurus bataar to be the sister taxon of T. rex. The discovery of the tyrannosaurid Lythronax further indicates that Tarbosaurus and Tyrannosaurus are closely related, forming a clade with the Asian tyrannosaurid Zhuchengtyrannus, with Lythronax being its sister taxon. Another 2016 study by Steve Brusatte, Thomas Carr and colleagues also indicates that Tyrannosaurus may to have been an immigrant from Asia, as well as a possible descendant of Tarbosaurus.
Phylogeny
Below is the cladogram of Tyrannosauridae based on phylogenetic analysis by Loewen et al. in 2013.
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Paleobiology
Brain and senses
A study by Lawrence Witmer and Ryan Ridgely of Ohio University found that Tyrannosaurus shared the enhanced sensory abilities of other coelurosaurs, featuring relatively rapid and coordinated eye and head movements, a enhanced ability to detect low-frequency sounds, which would allow Tyrannosaurus to track the movements of their prey from long distances, and an enhanced sense of smell. A study published by Kent Stevens concluded that Tyrannosaurus had keen vision. By applying modified perimetry to facial reconstructions of several dinosaurs, including Tyrannosaurus, the study found that Tyrannosaurus had a binocular range of 55 degrees, surpassing that of modern falcons. Stevens estimated that Tyrannosaurus had thirteen times the visual acuity of a human and surpassed the visual acuity of an eagle, which is 3.6 times that of a person. Stevens estimated a far point limit, that is, the distance at which an object can be seen apart from the horizon, up to 6,000 meters away, which is greater than the 1,600 m that a human being can see.
Thomas Holtz Jr. would point out that the high depth perception of Tyrannosaurus may be due to the prey it had to hunt, noting that it had to hunt horned dinosaurs such as Triceratops, armored dinosaurs such as Ankylosaurus and duck-billed dinosaurs and their possibly complex social behaviors. He would suggest that this made accuracy more crucial for Tyrannosaurus to allow it to "go in, land that punch and take it down". In contrast, Acrocanthosaurus had limited depth perception because they hunted large sauropods, which were relatively rare during the time of Tyrannosaurus.
Tyrannosaurus had very large olfactory bulbs and olfactory nerves relative to the size of its brain, the organs responsible for a heightened sense of smell. This suggests that the sense of smell was highly developed and implies that Tyrannosaurus could detect carcasses by scent alone at great distances. The sense of smell in Tyrannosaurus may have been comparable to that of modern vultures, which use scent to track carcasses for food. Research on the olfactory bulbs has shown that T. rex had the most highly developed sense of smell of the 21 non-avian dinosaur species sampled.
Somewhat unusual among theropods, T. rex had a very long cochlea. Cochlea length is often related to hearing acuity, or at least to the importance of hearing in behavior, implying that hearing was a particularly important sense for Tyrannosaurus. Specifically, the data suggest that T. rex heard best in the low-frequency range and that low-frequency sounds were an important part of Tyrannosaurus behavior. A 2017 study by Thomas Carr and colleagues found that the tyrannosaurid snout was highly sensitive, based on a large number of small openings in the facial bones of the related Daspletosaurus that contained sensory neurons. The study speculated that tyrannosaurids might have used their sensitive snouts to gauge the temperature of their nests and gently scoop up eggs and hatchlings, as seen in modern crocodiles. Another study published in 2021 further suggests that Tyrannosaurus had a keen sense of touch, based on neurovascular channels in the front of its jaws, which it could use to better detect and consume prey. The study, published by Kawabe and Hittori et al., suggests that Tyrannosaurus could also accurately sense slight differences in material and movement, allowing it to use different strategies feeding on different parts of the carcasses of their prey depending on the situation. The sensitive neurovascular canals of Tyrannosaurus have also likely been adapted for fine movements and behaviors, such as nest building, brood care, and other social behaviors, such as intraspecific communication. The results of this study are also in line with results obtained from studying the related tyrannosaurid Daspletosaurus horneri and the allosauroid Neovenator, which have similar neurovascular adaptations, suggesting that the faces Most theropods were highly sensitive to pressure and touch. However, a more recent study reviewing the evolution of trigeminal canals among saurops suggests that a much denser network of neurovascular canals in the snout and mandible inferior is more commonly found in aquatic or semi-aquatic taxa; for example, Spinosaurus, Halszkaraptor, Plesiosaurus and taxa that developed a ramphotheca such as Caenagnathasia while the channel network in Tyrannosaurus it appears simpler, though still more derived than in most ornithischians, and terrestrial taxa in general, such as tyrannosaurids and Neovenator, may have had facial sensitivity average for non-edentulous terrestrial theropods, although more research is needed. In contrast, neurovascular canals in Tyrannosaurus may have supported soft tissue structures for thermoregulation or social signaling, the latter of which could be confirmed by the fact that the neurovascular canal network may have changed during ontogeny.
A study by Grant R. Hurlburt, Ryan C. Ridgely, and Lawrence Witmer obtained estimates of encephalization quotients (EQs), based on reptiles and birds, as well as estimates of the ratio of brain to brain mass. The study concluded that Tyrannosaurus had the relatively largest brain of all non-avian adult dinosaurs with the exception of certain small maniraptoriforms, Bambiraptor, Troodon and Ornithomimus. The study found that the relative brain size of Tyrannosaurus was still within the range of modern reptiles, being at most two standard deviations above the mean for non-avian reptile equalizers. Estimates of the ratio between brain masses would range from 47.5 to 49.53%. According to the study, this is more than the lowest estimates for extant birds of 44.6 percent, but still close to typical ratios for the smallest sexually mature alligators, which range from 45.9 to 47.9. %. Other studies, such as those of Steve Brusatte, indicate that the encephalization ratio of Tyrannosaurus was similar in range, 2.0 to 2.4, to that of a chimpanzee, 2.2 to 2.5, although this may be debatable since the encephalization ratios of reptiles and mammals are not equivalent.
Posture
Tyrannosaurus, like all theropods, was bipedal. Its legs were endowed with a padded fabric that also functioned as a spring. The long bones of the legs were fused together to transmit the forces generated by their heavy footfalls, through the legs, to the rest of the body. Like many other bipedal dinosaurs, in the 19th and 20th centuries Tyrannosaurus rex was erroneously described as having three stances on the ground, tripod position, with the body at 45 degrees or less in an upright posture. and the tail dragging on the ground, similar to a kangaroo. This concept dates from 1865, when Joseph Leidy made the reconstruction of Hadrosaurus, the first description of a dinosaur in a bipedal posture. Henry Fairfield Osborn, former president of the American Museum of Natural History in New York, believed that the creature could stand upright and further reinforced this idea when the first complete skeleton of Tyrannosaurus rex was exposed to the public in 1915, which remained in this upright position for 77 years, until it was dismantled in 1992.
In the 1970s, scientists realized that this posture was incorrect as it could not have been held by a living animal; would have resulted in the dislocation or weakening of several joints, including femorischial joints of the hips and the atlantoccipital joint, between the head and the spine. The American Museum's inaccurate mounting has inspired many similar depictions in films and paintings, such as the mural The Age of Reptiles at the Peabody Museum at Yale University. This was until the 1990s, when films such as Jurassic Park presented a more accurate stance to the public. in general. Modern representations of T. rex in museums, art, and film show its body roughly parallel to the ground and its tail extended behind to balance its head.
To sit up, Tyrannosaurus may have shifted its weight back and rested its weight on a pubic boot, the wide expansion at the end of the pubis in some dinosaurs. With its weight resting on its pelvis, it may have been free to move its hind legs. Getting back up might have involved some stabilization of the tiny forelimbs. The latter, known as Newman's theory of pushups, has been debated. However, Tyrannosaurus could probably get up if it fell, which would only have required placing the limbs below the center of gravity, with the tail as an effective counterbalance. Healed stress fractures in the forelimbs have been advanced as evidence that the arms could not have been very useful, and as evidence that they were indeed used and acquired injuries, like the rest of the body.
Upper Extremities
Tyrannosaur upper limbs were relatively small compared to the rest of the body, but they were not vestigial organs, as they had large areas for muscle attachment, giving them considerable strength. They had two toes and not three, as was mistakenly believed, until it was confirmed in 1989, when the relatively complete front legs of Tyrannosaurus rex were found, belonging to MOR 555, the Wankel rex. Sue's remains also include complete front legs.
When the first specimen of Tyrannosaurus rex was discovered, the upper extremities were not found. To complete the original skeleton, which was assembled for public display, Osborn replaced that remaining part with the more long three-fingered arms of an Allosaurus. However, in 1914, Lawrence Lambe described a two-fingered forepaw for the closely related Gorgosaurus. This strongly suggested that T. rex had similar forelimbs, but this hypothesis was not confirmed until the first complete forelimbs were identified in 1989, belonging to MOR 555, the Wankel rex. The arms of T. rex are very small in relation to overall body size; they are only one meter long, and have been labeled by some scholars as vestigial. However, the bones show large areas of muscle attachment, indicating considerable strength. Sue's remains also include complete forelimbs. The function of the upper limbs is disputed. In 1906 Osborn speculated that they might have served to entrap the pair during copulation. It has also been suggested that the forelimbs were used to help animals rise from a sternal recumbency position. Others have since been proposed. functions, although some scholars find them implausible.
Another possibility is that the forelimbs held down the prey during the fight, while the huge jaws of the tyrannosaur killed it. This hypothesis is supported by biomechanical analysis. The forelimb bones of Tyrannosaurus rex have very thick cortical bone, indicating that they developed to withstand heavy loads. The biceps brachii muscle of an adult Tyrannosaurus rex was capable of lifting 199 kilograms by itself, a number that would increase when acting with other muscles, such as the brachialis muscle. This last muscle in T. rex was 3.5 times more powerful than the human equivalent. On the other hand, the Tyrannosaurus forearm had limited freedom of rotation, with the shoulder and elbow allowing turns of only up to 40 and 45 degrees, respectively. By comparison, the same two joints in Deinonychus allowed movements of up to 88 and 130 degrees, respectively, whereas a human arm can rotate 360 degrees at the shoulder and move about 165 degrees at the elbow. The heavy foreleg bones, extreme muscle strength, and limited rotation may indicate an evolved system for holding steady despite the stresses caused by struggling prey. In the first detailed scientific description of Tyrannosaurus forelimbs, paleontologists Kenneth Carpenter and Matt Smith dismissed notions that forelimbs were useless or that Tyrannosaurus was a scavenger obligate. The idea that the arms served as weapons for hunting prey has also been advanced by Steven M. Stanley, who suggested that the arms were used to cut down prey, especially using the claws to rapidly inflict long, deep cuts on prey. This was rejected by Padian, who argued that Stanley based his conclusion on incorrectly estimated forelimb size and range of motion. Padian, in 2022, argued that the reduction of arms in tyrannosaurids served no function. particular rather it was a secondary adaptation, stating that as tyrannosaurids evolved larger and more powerful skulls and jaws, arms became they became smaller to avoid being bitten or torn by other individuals, particularly during group feeding.
Growth
The identification of several juvenile tyrannosaurs has allowed scientists to document ontogenetic changes in the species, estimate their lifespans, and determine how fast these animals grew. The smallest known specimen, [[Los Angeles County Museum of Natural History|LACM]] 28471, the Jordan theropod, is estimated to have weighed only 30 kilograms, while the largest, FMNH PR2081 nicknamed Sue, probably weighed more than 5,400. Histological analysis of the bones of LACM 28471 showed that she was only two years old when she died, while that Sue was 28 years old, an age that might be close to the maximum for the species.
Histology has also made it possible to calculate the age of other specimens. Growth curves can be developed by plotting the body mass of different specimens against their age. The growth curve for Tyrannosaurus rex is S-shaped. Juveniles do not exceed 1,800 kg until about fourteen years of age, when body size begins to increase dramatically. During this rapid growth phase, a young Tyrannosaurus was to gain an average of 600 kg per year for the next four years. At eighteen years of age, the curve becomes almost horizontal, indicating a drastic slowdown in growth. For example, only 600 kg separate Sue's 28-year-old from the 22-year-old of a Canadian specimen, RTMP 81.12.1. Another recent histological study by different scientists corroborates these results, finding that rapid growth began to slow down around sixteen years of age. This sudden change in growth rate could be a sign of physical maturity, a hypothesis that is supported by the discovery of medullary tissue in the femur of a Sixteen to twenty year old Tyrannosaurus from Montana, MOR 1125, also known as B-rex. Marrow tissue is found only in female birds during ovulation, indicating that B-rex could be a female of reproductive age. The age of B-rex b> has been estimated to be around eighteen years. In 2016, Mary Higby Schweitzer and Lindsay Zanno and colleagues finally confirmed that the soft tissue within the femur of MOR 1125 was medullary tissue. This also confirmed the identity of the specimen as a female. The discovery of medullary bone tissue within Tyrannosaurus may prove valuable in determining the sex of other dinosaur species in future examinations, as the chemical composition of the medullary tissue is unmistakable. Other tyrannosaurids exhibit growth curves similar, although with slower growth rates resulting in smaller sizes in adulthood.
A study by Hutchinson and colleagues in 2011 corroborated earlier estimation methods in general, but their estimate of maximum growth rates is significantly higher. He found that the "maximal growth rates for T. rex during the exponential stage is 1790 kg per year". Although these results were much higher than previous estimates, the authors noted that these results significantly reduced the large difference between their actual growth rate and the than would be expected from an animal of its size.
An additional study published in 2020 by Woodward and colleagues for the journal Science Advances indicates that during its growth from juvenile to adult, Tyrannosaurus was able to slow its growth to counteract environmental factors such as lack of food. The study, which focused on two juvenile specimens between thirteen and fifteen years old housed at the Burpee Museum in Illinois, indicates that the rate of Tyrannosaurus maturation depended on the abundance of resources. This study also indicates that in such changing environments, Tyrannosaurus was particularly well adapted to an environment that changed in abundance of resources every year, indicating that other medium-sized predators might have had a difficult time surviving. in such harsh conditions and explained the division of niches between Tyrannosaurus juveniles and adults. The study further indicates that Tyrannosaurus and the dubious genus Nanotyrannus are synonymous, due to analysis of growth rings in the bones of the two specimens studied.
More than half of known Tyrannosaurus specimens appear to have died less than six years after reaching sexual maturity, a pattern also seen in other tyrannosaurids and now in some mammals and birds great long life These species are characterized by high infant mortality rates, followed by relatively low mortality among the young. Mortality increases again after sexual maturity, partly due to reproductive stresses. A study suggests that the paucity of juvenile Tyrannosaurus rex fossils is due in part to low juvenile mortality rates. However, this scarcity could also be due to the incompleteness of the fossil record or to collector bias toward larger, more spectacular fossil specimens. In a 2013 lecture, Thomas Holtz Jr. suggested that dinosaurs "lived fast." and they died young" because they reproduced quickly, while mammals have a long lifespan because they take longer to reproduce. Gregory S. Paul also writes that Tyrannosaurus reproduced quickly and died young, but attributes its short lifespan to the conditions. dangerous in which they lived.
Sexual dimorphism
Doubts exist about the existence of sexual dimorphism, that is, significant external physical differences between males and females, in Tyrannosaurus.
In the 1990s, the increase in the number of specimens discovered made it possible to analyze the differences between individuals and discover what seemed to be two different types of conformation, called morphotypes: one called "robust", solidly built, and the other called "gracile". ». The "robust" morph was thought to be characteristic of females, as the greater width of their pelvis might have served to allow the passage of eggs. In addition, the "robust" morph was considered to be correlated with a chevron reduced in the first tail vertebra, something that at the time was mistakenly thought in the case of crocodiles also facilitated hatching. correlated with a reduced chevron on the first tail vertebra, also apparently to allow eggs to exit the reproductive tract, as had been erroneously reported for crocodiles.
In recent years, the arguments for sexual dimorphism have weakened. In 2005 it was reported that previous claims of sexual dimorphism in the chevron anatomy of crocodiles were erroneous. A life-size chevron was found on the first tail vertebra of Sue, a very robust individual, which indicating that this characteristic cannot be used to differentiate the two morphotypes of Tyrannosaurus rex anyway. As specimens of this species have been found over a wide geographic area from Saskatchewan (Canada) to New Mexico (southwestern United States), it could be that morphological differences between individuals are due to geographic variation rather than to sexual dimorphism. The differences could also be related to age, with robust individuals being the oldest animals.
It has only been possible to conclusively determine the gender, female or male, of a single specimen of Tyrannosaurus, the nickname B-rex. Some of the soft tissue preserved within their bones has been identified as medullary tissue, a specialized tissue found exclusively in modern birds, as a source of calcium for eggshell production during ovulation. Since only females lay eggs, medullary tissue is only found naturally in females, although males are capable of producing it when injected with female reproductive hormones such as estrogen. This strongly suggests that B-rex was a female, and that it died during ovulation. Recent research has shown that the marrow tissue is not found in crocodiles, which are believed to be the closest living relatives close relatives of dinosaurs, as well as birds. The shared presence of medullary tissue in birds and theropod dinosaurs is further evidence of the close evolutionary relationship between the two.
Soft fabric
In the March 2005 issue of Science, Mary Higby Schweitzer of North Carolina State University and colleagues announced the recovery of soft tissue from the medullary canal of a fossilized leg bone of a Tyrannosaurus rex. The bone had been intentionally, albeit grudgingly, broken for shipment and then not preserved in the normal way, specifically because Schweitzer hoped to test it for soft tissue. Designated specimen MOR 1125, the dinosaur was previously excavated from the Hell Creek Formation. Flexible, bifurcated blood vessels, and fibrous but elastic bone. Matrix tissues were recognized. Furthermore, microstructures resembling blood cells were found within the matrix and vessels. The structures bear resemblance to ostrich blood cells and blood vessels. Whether an unknown process other than normal fossilization preserved the material, or whether the material is original, the researchers do not know and are careful not to make claims about preservation. If found to be original material, any surviving proteins it can be used as a means of indirectly guessing at some of the DNA content of the dinosaurs involved, because each protein is usually created by a specific gene. The lack of previous findings may be the result of people assuming that preserved tissue was impossible and therefore did not search. Since the first, two other Tyrannosaurus and a hadrodaurid have also been found to have tissue-like structures. Research on some of the tissues involved has suggested that birds are closer relatives of tyrannosaurids than other modern animals.
In studies reported in Science in April 2007, Asara and colleagues concluded that seven trace amounts of collagen proteins detected in bones purified from T. rex most resemble those reported in chickens, followed by frogs and newts. The discovery of proteins from a tens-of-million-year-old creature, along with similar traces the team found in a mastodon bone at least 160,000 years old, changes the conventional view of fossils and may change paleontologists' approach to history. search of bones to biochemistry. Until these findings, most scientists assumed that fossilization replaced all living tissue with nonliving minerals. Paleontologist Hans Larsson of McGill University in Montreal, who was not part of the studies, called the finds "a milestone" and suggested that dinosaurs could "enter the field of molecular biology and really launch paleontology into the modern world".
The alleged soft tissue was questioned by Thomas Kaye of the University of Washington and his co-authors in 2008. They argue that what was really inside the Tyrannosaurus bone was a slimy biofilm created by bacteria that covered the gaps once occupied by blood vessels and cells. The researchers discovered that what had previously been identified as remnants of blood cells, due to the presence of iron, were actually framboids, microscopic mineral spheres containing iron. They found similar spheres in a variety of other fossils from various periods, including an ammonite. In the ammonite they found the spheres in a place where the iron they contain could have had no relation to the presence of blood. Schweitzer has strongly criticized Kaye's claims and argues that there is no reported evidence that biofilms can produce branched hollow tubes. like those seen in their study. San Antonio, Schweitzer, and colleagues published an analysis in 2011 of which parts of the collagen had been recovered and found that it was the inner parts of the collagen coil that had been preserved, as expected after a long period of protein degradation. Other research challenges the identification of soft tissue as biofilm and confirms the finding of "branched vessel-like structures" inside the fossilized bone.
Fur and feathers
As of 2022, there is no direct evidence either for or against the fact that T. rex had feathers. However, many of their close relatives did, and scientists acknowledge the possibility that they did, too. Remains of small coelurosaurians, the group of dinosaurs to which Tyrannosaurus belongs, have been found., from the Yixian Formation of Liaoning, China, which had pennaceous feathers or ancient protofeather fur, suggesting the possibility that tyrannosaurids may have had feathers as well. The ancient tyrannosauroid Dilong paradoxus, discovered in the same formation, also showed protofeather filaments on its tail. However, skin impressions of adult tyrannosaurs from Alberta and Mongolia appear to show the scaled scales typical of other dinosaurs. It has been hypothesized that the presence of feathers or scales could be a function of the size of the animal or its geographic location. In cold climates the feathers would have been useful as thermal insulation, but not in hot climates. Similarly, a feather cover would have overheated larger animals, since in warm-blooded animals the amount of heat generated is a function of the volume of the animal while its cooling is a function of the outer surface, and the ratio between the exposed surface and the body volume decrease the larger the size of the animal. It is possible that T. rex will have feathers or protofeathers on other regions of the body, but, as occurs with the hair of modern elephants and rhinos, in reduced areas. Protofeathers may have been lost during the evolution of large tyrannosaurids such as Tyrannosaurus, especially in warm Cretaceous climates.
The later discovery of the giant species Yutyrannus huali, also from the Yixian, showed that even some large tyrannosauroids had feathers covering much of their bodies, casting doubt on the hypothesis that they were a size-related characteristic. A 2017 study reviewed known tyrannosaurid skin impressions, including those of a Tyrannosaurus specimen nicknamed Wyrex, BHI 6230, which preserves patches of mosaic scales on the tail, hip, and neck. The study concluded that the feather cover of large tyrannosaurids such as Tyrannosaurus was, if present, limited to the upper part of the trunk.
A conference abstract published in 2016 postulated that theropods such as Tyrannosaurus had upper teeth covered with lips, rather than the bare teeth seen in crocodiles. This was based on the presence of enamel, which the study found needs to remain hydrated, a problem aquatic animals such as crocodiles do not face. A 2017 analytical study proposed that tyrannosaurids had large, flat snout scales in instead of the lips. However, there have been critics who favor the idea of the lips. Crocodiles don't actually have flat scales but cracked keratinized skin. By looking at the roughness of tyrannosaurid mounds and comparing it to extant lizards, they found that tyrannosaurids had scaly scales instead of crocodile-like skin.
Thermoregulation
It is unclear whether tyrannosaurs were ectothermic, meaning "cold-blooded," or endothermic, "warm-blooded." Until the 1960s, tyrannosaurs, and most dinosaurs, were thought to be ectothermic, "cold-blooded," with a reptilian metabolism. The idea of dinosaur ectothermy was challenged by scientists such as Robert T. Bakker and John Ostrom in the early years of the 'Dinosaur Renaissance'. Bakker and Ostrom argued that Tyrannosaurus must have been endothermic, "warm-blooded," implying a highly active lifestyle. Paleontologists are still trying to determine the Tyrannosaurus's ability to regulate its body temperature. The high growth rates of young Tyrannosaurus rex, as measured by histological analysis, are comparable to those of mammals and birds, and thus support the hypothesis of high metabolism. Growth curves indicate that, as in mammals and birds, growth in T. rex was mostly confined to immature animals, rather than the indeterminate growth seen in most other vertebrates.
The ratios of oxygen isotopes in fossilized bones are sometimes used to determine the temperature at which they are deposited in the bone, since the ratio between certain isotopes correlates with temperature. A study of Tyrannosaurus bones found that isotope ratios indicated a temperature difference of no more than four to five °C between the vertebrae of the trunk and the tibia of the lower leg. This small temperature range between the core of the body and the extremities was used by paleontologist Reese Barrick and geochemist William Showers to indicate that Tyrannosaurus rex maintained a constant body temperature, homeothermy, and that they enjoyed a metabolism intermediate between that of ectothermic reptiles and endothermic mammals. Other scientists have pointed out, however, that the ratio of oxygen isotopes in fossils today does not necessarily present the same relationship as in the distant past, and it may have been altered during or after fossilization, in a process called diagenesis. Barrick and Showers have defended their conclusions in subsequent work, finding similar results in another theropod dinosaur from a different continent tens of millions of years apart, Giganotosaurus. Ornithischian dinosaurs also showed evidence of homeothermy, while monitor lizards of the same form mation No. In 2022, Wiemann and his colleagues used a different approach. Spectroscopy of lipoxidation signals, which are byproducts of oxidative phosphorylation and correlate with metabolic rates, to demonstrate that several genera of dinosaurs, including Tyrannosaurus, had endothermic metabolisms, on par with the of modern dinosaurs, birds, and greater than that of mammals. They also suggested that such metabolism was ancestrally common to all dinosaurs.
Although Tyrannosaurus rex shows signs of homeothermy, this does not necessarily mean that it is endothermic. Thermoregulation may also be explained by gigantothermy, as occurs in some extant sea turtle species. As in contemporary crocodiles, openings, dorsotemporal fenestrae, in the roofs of the Tyrannosaurus skull may have helped to thermoregulation.
Locomotion
Tyrannosaurus had fairly long legs, but there is disagreement about how fast it could move. Some scientists think that in heavy animals the legs that are located under the body are like pillars, with large bones to support the weight but that do not allow them to run. The calculations range from a leisurely speed of 1 m/s (5 km/h) to a very fast 5 m/s (19 km/h). Scientists who believe that T. rex moved quickly indicate that its legs were similar to those of ornithomimids as fast as Struthiomimus. A recent study concluded, however, that T. rex didn't have enough leg muscle mass to be that fast; what he did was walk taking strides of 4 m for each step, giving him a speed of 5 m/s. Many footprints of walking theropods have been found but so far none of running theropods. This makes it impossible to calculate their speed and could otherwise indicate that they were indeed not capable of running. Scientists have produced a wide range of possible maximum running speeds for Tyrannosaurus, mostly around 9 m/s (32 km/h), with the lowest being around 4.5 to 6.8 m/s (16 to 24 km/h) and as high as 20 m/s (72 km/h), although it is highly unlikely that he ran at this speed. Tyrannosaurus was a bulky and heavy carnivore, so it is unlikely that it ran very fast compared to other theropods such as Carnotaurus or Giganotosaurus. Researchers have relied on various estimation techniques, because while there are many tracks of large walking theropods, none showed evidence of running.
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Bipeds are at greater risk of falling if they stumble during a start, and cannot accommodate their legs under their bodies. The falls were very dangerous for T. rex because the head traveled more than 3 m in the collapse, and the front legs could not break its fall. Ostriches have a similar problem, but the risk of falling from an ostrich or other ratites is far less than it would have been for a T-rex even as this predator (if it was hunting live prey). If T. rex fell hard and could be injured and even killed. Researchers calculated that if a T. rex were to run at a speed of 12 mph and trip, he would hit the ground with such force that he would break muscles and bones, killing him. But another team of researchers came up with a more plausible proposal. It is about the possibility that T. rex moved between 7 and 19 km/h, similar to the top speed of an African elephant. Christiansen, in 1998, estimated that the leg bones of Tyrannosaurus were not significantly stronger than those of elephants, which are relatively limited in their maximum speed and never run, since they do not present the phase of air, and therefore proposes that the maximum speed of dinosaurs has been about 4 m/s (19 km/h), which refers to the speed of a human sprinter. But he also pointed out that these estimates depend on many dubious assumptions.
Farlow and colleagues in 1995 have argued that a Tyrannosaurus weighing 5.4 to 7.3 tons would have been seriously or even fatally injured if it had fallen while moving rapidly, since that its torso would have crashed to the ground with a deceleration of 6 g (six times the acceleration of gravity, or about 60 m/s²) and the small front legs could not have reduced the impact. However, it is known that giraffes gallop at 13.8 m/s (50 km/h), despite the risk that they could break a leg or worse, becoming deadly, even in a 'safe' environment; like a zoo. Therefore, it is quite possible that Tyrannosaurus also moved quickly when necessary and accepted such risks.
Most recent research on Tyrannosaurus locomotion is not compatible with a speed of 11.1 m/s (40 km/h), that is, developing a moderate speed. For example, a 2002 paper in the journal Nature used a mathematical model, validated by application to three classes of living things: alligators, birds, and humans. Eight other species, including emus and ostriches, were later included to measure the mass of leg muscle needed for rapid running of more than 11 m/s. Scientists who believe Tyrannosaurus could run suggest that hollow bones and other features that would have lightened its body may have kept adult weight to just 4.5 metric tons or so, or that other animals such as ostriches and horses with long, flexible legs can reach tall speeds with slower but longer strides. They found that aiming for a maximum speed of more than 11 m/s (40 km/h) was unfeasible, because it would require very large leg muscles, approximately 40-86% of the total body mass. Even moderately fast speeds would have required large leg muscles. This discussion is difficult to resolve, since it is not known how large the leg muscles were in Tyrannosaurus; if they were small, it would only have reached 5 m/s (18 km/h), possibly barely a speed suitable for walking or jogging. Holtz noted that tyrannosaurids and some closely related groups had significantly longer distal hindlimb components (shin, foot, and toes) relative to femur length than most other theropods, and that tyrannosaurids and their close relatives had a closely interlocking metatarsal, the bones of the foot. The third metatarsal was compressed between the second and fourth metatarsals to form a single unit called the arctometatarsals. This ankle feature may have helped the animal run more efficiently. Together, these leg features allowed Tyrannosaurus to transmit locomotor forces from the foot to the lower leg with more efficiency than in earlier theropods.
Some argue that Tyrannosaurus was incapable of running, estimating the top speed at around 17 km/h. This slower speed is still superior to that of its likely prey, hadrosaurids and ceratopsians. Furthermore, some proponents of the idea that Tyrannosaurus was a predator claim that the speed of Tyrannosaurus in pursuit is not important, as it may have been slow, but still faster than its prey. However, Paul and Christiansen, in 2000, argued that at least the latest ceratopsians had upright forelegs and the largest species may have been as fast as rhinos. Healed bite wounds in ceratopsian fossils are interpreted as evidence of tyrannosaur attacks on ceratopsians during life. This calls into question the argument that Tyrannosaurus did not have to be fast to catch its prey, since the ceratopsians that lived alongside it were fast.
A 2007 study used computer models to calculate gait speed, based on data obtained directly from fossils, and concluded that Tyrannosaurus had a maximum forward speed of eight meters per second. The average professional soccer player would be a bit slower, while a human sprinter can reach 4 m/s (19 km/h). Note that these computer models predict a maximum speed of 6 m/s (21 km/h) for a small 3 kg Compsognathus, probably a juvenile.
A 2017 study estimated the maximum running speed of Tyrannosaurus at 7.5 m/s (27 km/h), speculating that Tyrannosaurus exhausted its energy reserves. energy well before reaching maximum speed, resulting in a parabola-like relationship between size and speed. Another 2017 study hypothesized that an adult Tyrannosaurus was incapable of running due to high skeletal loads. Using a calculated weight estimate of seven tons, the model showed that speeds greater than 5 m/s (18 km/h) would likely have shattered the leg bones of Tyrannosaurus. The finding may mean that running was also not possible for other giant theropod dinosaurs such as Giganotosaurus, Mapusaurus and Acrocantosaurus. However, Eric's studies Snively and colleagues, published in 2019, indicate that Tyrannosaurus and other tyrannosaurids were more maneuverable than allosauroids and other theropods of comparable size due to low rotational inertia compared to their body mass combined with large muscles. in the legs. As a result, it is hypothesized that Tyrannosaurus was capable of relatively fast turns and was probably able to pivot its body more rapidly when close to its prey, or while turning, the theropod could " do pirouettes" on a single planted foot while the alternate leg was held in the air. The results of this study could shed light on how agility might have contributed to successful tyrannosaurid evolution.
A 2020 study indicates that Tyrannosaurus and other tyrannosaurids were exceptionally efficient walkers. Studies by Dececchi et al., compared the leg proportions, body mass, and gait of more than 70 species of theropod dinosaurs, including Tyrannosaurus and their relatives. The research team then applied a variety of methods to estimate each dinosaur's top speed when running, as well as the amount of energy each dinosaur expended while moving at more relaxed speeds, such as when walking. Among smaller to medium-sized species such as dromaeosaurids, longer legs appear to be an adaptation for faster running, in line with previous results from other researchers. But for theropods weighing more than 1,000 kg, maximum running speed is limited by body size, so longer legs were found to correlate with low-energy walking. The results further indicate that the smaller theropods evolved long legs as a means both to aid in hunting and to escape larger predators, while the larger theropods that evolved long legs did so to reduce energy costs and increase foraging efficiency. as they were freed from the demands of predation pressure due to their role as apex predators. Compared to more basal groups of theropods in the study, tyrannosaurids such as Tyrannosaurus itself showed a marked increase in foraging efficiency due to reduced energy expenditures during hunting or foraging. harvest. This, in turn, probably resulted in Tyrannosaurus having a reduced need for hunting raids and, as a result, requiring less food to sustain themselves. Furthermore, the research, along with studies showing that tyrannosaurids were more agile than other large-bodied theropods, indicates that they were quite well adapted to a long-distance stalking approach followed by a quick burst of speed for the kill. As a result, analogies between tyrannosaurids and modern wolves can be seen, supported by evidence that at least some tyrannosaurids hunted in packs.
A study published in 2021 by Pasha van Bijlert et al. calculated the preferred gait speed of Tyrannosaurus, reporting a speed of 1.28 m/s (4.6 km/h). While walking, animals reduce their energy expenditure by choosing certain gait rhythms in which their body parts resonate. The same would have been true for dinosaurs, but previous studies didn't fully explain the impact the tail had on their walking speed. According to the authors, when a dinosaur walked, its tail bobbed slightly up and down with each step as a result of the interspinous ligaments, suspending the tail. Like rubber bands, these ligaments store energy when they are stretched due to the swinging of the tail. Using a three-dimensional model of the Trix specimen of Tyrannosaurus, muscles and ligaments were reconstructed to simulate tail movements. This results in an energetically efficient, rhythmic walking speed for Tyrannosaurus similar to that seen in living animals such as humans, ostriches, and giraffes.
Footprints
Attributing a certain footprint to a Tyrannosaurus is risky, since the feet of the different theropods all leave very similar tridactyl, three-toed footprints. However, they have been provisionally assigned to Tyrannosaurus two isolated fossil footprints.
The first was discovered at Philmont Scout Ranch, New Mexico, in 1983, by American geologist Charles Pillmore. Originally they were thought to belong to a hadrosaurid; however, examination of the track revealed a large "heel print", unknown in ornithopods, and indications of what may have been the spur, such as the fourth digit of the foot of a Tyrannosaurus. The print gave rise to a new ichnogenus and ichnospecies, Tyrannosauripus pillmorei, published in 1994 by Martin Lockley and Adrian Hunt. These authors suggested that it was most likely made by a Tyrannosaurus rex, which would make it the first known print of this species. The footprint, 83 centimeters long by 71 centimeters wide, was imprinted in what was once the muddy bed of a vegetated wetland.
A second footprint that may have been made by a Tyrannosaurus was discovered in 2007 by British paleontologist Phil Manning, in Montana's Hell Creek Formation and published in 2008 by Manning, Ott, and Falkingham. It measures 72 centimeters long by 76 wide, shorter and somewhat broader than that described by Lockley and Hunt. Whether the footprint was made by Tyrannosaurus or not is unclear, although Tyrannosaurus is the only large theropod known for certain to have existed in the Hell Creek Formation. Possible candidates for the authorship of this footprint are Tyrannosaurus or Nanotyrannus, if not synonymous with Tyrannosaurus, the only large theropods known from the Formation Hell Creek, although it could belong to some other yet unknown carnivorous dinosaur.
Scott Persons, Phil Currie, and colleagues described a set of footprints in Glenrock, Wyoming, dating to the Late Cretaceous Maastrichtian stage from the Lance Formation in 2016, and are believed to belong to a T. rex juvenile or the dubious tyrannosaurid Nanotyrannus lancensis. From the measurements and based on the positions of the tracks, the animal was believed to be traveling at a speed of around 14 to 29 m/s and was estimated to have a hip height of 1.56 metres. A follow-up document appeared in 2017, increasing speed estimates by 50-80%.
Rare fossil tracks and tracks found in New Mexico and Wyoming that are assigned to the ichnogenus Tyrannosauripus have been attributed to Tyrannosaurus, based on the stratigraphic age of the rocks in which they they are conserved. The first specimen, found in 1994, was described by Lockley and Hunt and consists of a single large footprint. Another pair of ichnofossils, described in 2021, show a large tyrannosaurid rising from a prone position by rising up using its elbows along with the balls of its feet to stand up. These two unique sets of fossils were found in Ludlow, Colorado, and Cimarron, New Mexico. Another ichnofossil described in 2018, perhaps belonging to a juvenile tyrannosaur or to the dubious genus Nanotyrannus, was discovered in the Formation Wyoming lance. The trail itself offers a rare glimpse into the walking speed of tyrannosaurids, with the hunter estimated to have been moving at a speed of 1.25 to 2.2 m/s (4.5 to 8.0 km/h).), significantly faster than previously assumed for estimates of walking speed in Tyrannosaurus.
Social behavior
Philip J. Currie suggested that Tyrannosaurus may have been a pack hunter, comparing T. rex with related species (Tarbosaurus bataar and Albertosaurus sarcophagus), citing fossil evidence that may indicate gregarious behavior, describing animals that travel in herds or groups. A find in South Dakota where three skeletons of T. rex that were in close proximity may suggest the formation of a pack. Cooperative hunting in packs may have been an effective strategy to subdue prey with advanced adaptations against predators that pose potential lethality, such as Triceratops and Ankylosaurus.
The T hypothesis. rex Currie's pack hunter has been criticized for not being peer-reviewed, instead being discussed in a television interview and a book called Dino Gangs. Currie's theory for pack hunting by T. rex is based primarily on analogy with a different species, Tarbosaurus bataar. Evidence for gregariousness in T. bataar itself has not been peer-reviewed and, by Currie's admission, can only be interpreted with reference to evidence in other closely related species. According to Currie, gregariousness in Albertosaurus sarcophagus is supported by the discovery of 26 individuals of varying ages in the bone bed of Dry Island. He ruled out the possibility of a predator trap due to the similar conservation status of the individuals and the near absence of herbivores.
Additional support for tyrannosaurid gregariousness can be found in fossilized tracks from the Late Cretaceous Wapiti Formation of northeastern British Columbia, Canada, left by three tyrannosaurids traveling in the same direction. According to scientists who evaluate the Dino Gangs program, the evidence for pack hunting in Tarbosaurus and Albertosaurus is weak and based on group skeletal remains for which alternative explanations can be applied, such as a drought or flood that forced the dinosaurs to die together in one place. Other researchers have speculated that, rather than large social groups of theropods, some of these finds represent more Komodo dragon-like behavior, such as the carcass stalking, going so far as to say that true pack-hunting behavior may not exist in any non-avian dinosaurs due to its rarity in modern predators.
Joseph Peterson and his colleagues found evidence of intraspecific attack in the juvenile Tyrannosaurus nicknamed Jane. Peterson and his team discovered that Jane's skull showed healed puncture wounds to the upper jaw and snout that they believe came from another juvenile Tyrannosaurus . Subsequent CT scans of Jane's skull would further confirm the team's hypothesis, showing that the puncture wounds were from traumatic injury and that there was subsequent healing. The team would also state that Jane's injuries were structurally different from the induced injuries. by parasites found on Sue and that Jane's lesions were on her face while the parasite that infected Sue caused lesions on her lower jaw.
Food
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The large tyrannosaurus jaws were over four feet long and filled with sharp, massive 7.5-inch curved teeth. Using dynamic musculoskeletal models, one study calculated that their bite force was by far the most powerful estimated or recorded of any terrestrial animal, being capable of exerting a pressure force of 3.6 to 5.8 tons. A pliosaur, Pliosaurus funkei, a marine predator found in 2009 in the Arctic could have exerted four times the pressure with its bite, making it one of the few predators (if not the only one) that was able to overcome in this area to T. rex. Most paleontologists accept that Tyrannosaurus was both an active predator and scavenger, like most large carnivores. By far the largest carnivore in its environment, T. rex was likely an apex predator, feeding on hadrosaurids, armored herbivores such as ceratopsians and ankylosaurs, and possibly sauropods. A 2012 study by Karl Bates and Peter Falkingham found that Tyrannosaurus had the most powerful bite of any land animal that ever lived, finding an adult Tyrannosaurus that could have exerted 35,000 to 57,000 N of force on the hind teeth. Estimates were made by Mason B. Meers even higher in 2003. This allowed it to crush bones during repetitive bites and completely consume the carcasses of large dinosaurs. Stephan Lautenschlager and colleagues calculated that Tyrannosaurus was capable of opening its jaws at most about of 80 degrees, an adaptation necessary for a wide range of jaw angles to power the creature's strong bite. Tyrannosaurus, and most other theropods, probably p they grazed mainly carcasses with side tossing of the head, like crocodiles. The head was not as maneuverable as allosauroid skulls, due to the flat joints of the neck vertebrae.
Discussion about the eating habits of Tyrannosaurus
The debate about whether Tyrannosaurus was a predator or a pure scavenger is as old as the debate about its locomotion. A well-preserved skeleton of a close relative of Tyrannosaurus, Gorgosaurus, was described in 1917 and was concluded to be a pure scavenger because it showed very little wear to the teeth, for which also Tyrannosaurus could have been. This argument is no longer taken seriously in 2021 because theropods continually replace teeth. Since its first discovery, most scientists have assumed that Tyrannosaurus was a predator. This does not exclude that, like modern large predators, tyrannosaurs cleaned up carcasses found by chance or stole dead prey from other predators if the opportunity arose.Jack Horner, a hadrosaurid expert, is as of 2021 the main defender of the idea that Tyrannosaurus was exclusively a scavenger and did not actively hunt. Horner has presented several arguments to support his hypothesis:
- The front legs of Tyrannosaurus are short compared to those of other known predators, so Horner asserts that they did not have the strength to hold on to their prey.
- Tyrannosaurus had olfactory bulbs and large olfactory nerves in relation to their cerebral size. This suggests a very developed sense of olphate, so it could detect dead bodies long distances, as current vultures do. Opponents of the cigar hypothesis have used the example of vultures in the opposite sense, arguing that the hypothesis of the scavenger is unbelievable because modern pure scavengers are only large glittering birds, who use their sharp senses and the efficient energy of the plan to cover large areas with minimal energy spending. However, it has been estimated that an ecosystem as productive as the current Serengeti could provide enough spool for a great carrion theropode, as long as they were cold blood. The absence of terrestrial floats in modern ecosystems such as Serengeti can be due to the fact that the planned birds now do the job much more efficiently, while the large theropods would not have faced that competition for their ecological niche.
- The teeth Tyrannosaurus They could crush bones, and therefore could extract a maximum of food, bone marrow, from the remains of an animal, including the less nutritious parts. Karen Chin and her colleagues have found bone fragments in coprolites that attribute to tyrannosaurus, but point out that the teeth of a Tyrannosaurus They were not well suited to chew bones systematically to extract the bone marrow, as the hyenas do.
- Since at least some of their potential dams ran fast, the indications that Tyrannosaurus I was walking instead of running suggesting that I was a scavenger. On the contrary, recent studies suggest that Tyrannosaurus, although it was slower than the great modern terrestrial predators, it could well have been quick enough to hunt for the Great Poses and Hadrosaurids.
Other clues suggest hunting behavior in Tyrannosaurus. Its eye sockets are arranged so that the eyes face forward, giving it slightly better binocular vision than modern falcons. Horner also noted that the Tyrannosaurus lineage had a history of steadily improving binocular vision. It is not clear why natural selection would have favored this long-term trend if Tyrannosaurus had been pure scavengers, which would not have needed the advanced perspective perception provided by stereoscopic vision. In animals Modern binocular vision is present mainly in predators but not exclusively, since lemurs and primates, among other non-predators, also have it. A 2021 study looking at the vision and hearing of the small theropod Shuvuuia, to which Tyrannosaurus was compared, suggests that it was diurnal and would have hunted predominantly during the day, a characteristic it shared with Dromaeosaurus, a third dinosaur compared to Shuvuuia in the study.
A skeleton of the hadrosaurid Edmontosaurus annectens shows a lesion on its tail vertebrae inflicted by a Tyrannosaurus and later healed. The fact that the damage healed shows that Edmontosaurus survived an attack by a Tyrannosaurus during its lifetime; that is, Tyrannosaurus had attempted active predation. A similar find was made in 2007 and described by David Burnham et al. in 2013 consisting of two fused tail bones of Edmontosaurus that had the tip of a tooth from an adult Tyrannosaurus embedded, with evidence of new bone growth that developed around the tooth. Burnham and his colleagues suggested that this hadrosaurid survived the predator attack and this is definitive proof that Tyrannosaurus was a predator.
There is also evidence of an aggressive interaction between Triceratops and Tyrannosaurus, as partially healed Tyrannosaurus tooth marks appear on the frontal horn. and the squamous, a frill bone of the neck, from a Triceratops; the bitten horn was broken, with new bone growth in the fracture. It is not known what the exact nature of the interaction was; either animal could have been the aggressor. Examining the Sue specimen, paleontologist Peter Larson found a healed fracture in the fibula and tail vertebrae, scars on the facial bones, and a tooth from another Tyrannosaurus embedded in a neck vertebra. If true, this would constitute strong evidence for aggressive behavior among Tyrannosaurus, but whether it was competition for food, competition for sexual partners, or active cannibalism is not known. However, the most recent investigation of these Purported injuries have shown that most are infections rather than injuries or simply damage to fossils that occurred after death, and the few actual injuries are too general to prove conflict between individuals of the same species. A 2009 study showed that the holes in the skulls of several specimens could have been caused by parasites such as Trichomonas that normally infect birds.
Some researchers argue that if Tyrannosaurus was a scavenger, another dinosaur would have had to occupy the ecological position of top predator in the Late Cretaceous in Laurasia. The largest prey were marginocephali and ornithopods. The other tyrannosaurids resemble T. rex that only small dromaeosaurids would remain as potential top predators. In this sense, supporters of the pure scavenger hypothesis argue that the size and strength of Tyrannosaurus would have been sufficient to steal prey from smaller predators. Most paleontologists accept that Tyrannosaurus was both an active predator and a scavenger, like most large carnivores.
Modern carnivores are rarely strict predators or scavengers. Lions, for example, sometimes eat dead hyenas, and vice versa. Behavior depends on prey availability, among other factors. If tyrannosaurs were scavengers practicing kleptoparasitism, stealing prey hunted by true predators, their body mass would have been an intimidating factor in scaring away predators; contemporary undisputed predators, such as raptors, were much smaller and faster, so the presence of a giant, toothy scavenger would have caused them to flee or retreat.
Cannibalism
Evidence also strongly suggests that tyrannosaurs were at least occasionally cannibalistic. Evidence of cannibalism in the genus Tyrannosaurus was published in 2010. Several specimens of Tyrannosaurus were analysed, showing bite marks on their bones attributable to other tyrannosaurs. Tooth marks are found on the humerus, foot bones, and metatarsals, and this was considered evidence of opportunistic scavenging behavior, and not of injuries caused in intraspecific combat, between members of the same species. In a fight, it would presumably be difficult for a T. rex lean enough to bite its opponent's feet, so the teeth marks were most likely made on a corpse. That the markings appear on parts of the body with relatively little meat suggests that Tyrannosaurus was feeding on the carcass of a congener whose meatier parts had already been eaten. Fossils from the Fruitland Formation, the The Kirtland Formation, both of Campanian age, and the Maastichtian-age Ojo Álamo Formation, suggest that cannibalism was present in several genera of tyrannosaurids from the San Juan Basin. Evidence collected from specimens suggests opportunistic feeding behavior in tyrannosaurids that cannibalized members of their own species. As the bite marks were made on parts of the body with relatively sparse amounts of meat, it is suggested that the Tyrannosaurus fed on a carcass in which the meatiest parts had already been consumed. They were also open to the possibility of other tyrannosaurids practicing cannibalism.
Infectious saliva
It has been suggested that Tyrannosaurus saliva might have been pathogenic to its prey. This idea was first proposed by William Abler. Examining tyrannosaurid teeth between each denticle on the serrated edge of the teeth, he noted a space that could have retained meat fibers that would go into a state of putrefaction due to colonies of bacteria, giving Tyrannosaurus a deadly infectious bite, as has also been suggested in the case of the Komodo dragon. However, Jack Horner indicates that in Tyrannosaurus the edges of the tooth serrations were more cube-shaped while in Komodo dragon teeth they are rounded. Horner has further noted that the tooth of T. rex is solid, while the Komodo dragon's teeth are grooved.
Parental care
While there is no direct evidence that Tyrannosaurus cared for its young, the rarity of nest and juvenile tyrannosaur fossils has left researchers speculating; some have suggested that, like their closest living relatives, modern archosaurs, birds, and Tyrannosaurus crocodiles may have protected and nurtured their young. Some paleontologists often suggest that crocodiles and birds are modern analogues for the rearing of dinosaurs. There is direct evidence of parental behavior in other dinosaurs such as Maiasaura peeblesorum, the first discovered caring dinosaur to their young, as well as in more closely related oviraptorids, the latter suggesting parental behavior in theropods.
Pathologies
In 2001, Bruce Rothschild and others published a study examining the evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma rather than singular events, they are more likely to be caused by regular behavior than by other types of injuries. Of the 81 Tyrannosaurus foot bones examined in the study, one was found to have a stress fracture, while none of the 10 hand bones had stress fractures. The researchers found tendon avulsions only between Tyrannosaurus and Allosaurus. An avulsion injury left a hole in Sue's humerus, Tyrannosaurus rex, apparently located at the origin of the deltoid or teres major muscles. The presence of avulsion injuries that are limited to the forelimb and shoulder in both Tyrannosaurus and Allosaurus suggests that theropods may have had more complex and functionally different musculature. to that of birds. The researchers concluded that Sue's tendon avulsion was likely caused by struggling prey. The presence of stress fractures and tendon avulsions, in general, provides evidence of a "highly active" predation-based diet; rather than an obligate scavenger.
A 2009 study showed that the smooth-edged holes in the skulls of several specimens could have been caused by Trichomonas-like parasites that commonly infect birds. Severely infected individuals, including Sue and MOR 980, Peck's Rex, could have starved to death after feeding became increasingly difficult, according to the study. Previously, these holes had been explained by the bacterial bone infection Actinomycosis or by intraspecific attacks. A later study found that although trichomoniasis has many attributes of the proposed intraoral osteolytic model, several features support the assumption that it was the cause of death is less supportable by the evidence. For example, the sharp margins seen with little reactive bone shown in radiographs of Trichomonas infected birds are different from the reactive bone seen in T. rex affected. Furthermore, trichomoniasis can be rapidly fatal in birds, in fourteen days or less, albeit in its milder form, and this suggests that if Trichomonas as the protozoan is the culprit, the trichomoniasis was less acute in its Non-avian form of dinosaur during the Late Cretaceous. Finally, the relative size of these types of lesions is much larger in the throats of small birds, and may not have been sufficient to suffocate a T. rex.
A study of Tyrannosaurus specimens with tooth marks on the bones attributable to the same genus was presented as evidence of cannibalism. Tooth marks on the humerus, foot bones, and metatarsals may indicate opportunistic scavenging, rather than injuries caused by combat with another T. rex. Other tyrannosaurids may also have practiced cannibalism.
Paleoecology
Tyrannosaurus lived throughout western North America, from Alberta, Canada, to Coahuila, Mexico, just before the dinosaurs became extinct. Usually T. rex lived in floodplains and subtropical forests where it stalked its prey, in areas demarcated by rivers, lakes and lush forests full of cycads, ferns, flowering plants and trees such as conifers, sycamores and araucarias. It lived during what is known as the Lanciano faunal stage, Maastrichtian age, at the end of the Late Cretaceous. Tyrannosaurus ranged from Canada in the north to at least New Mexico in southern Laramidia. During this time, Triceratops was the major herbivore in the northern part of its range, while the titanosaur sauropod Alamosaurus "dominated" its southern range. Tyrannosaurus remains have been discovered in different ecosystems, including inland and coastal subtropics, and semi-arid plains. Tyrannosaurus is believed to have required large ranges for feeding, due to the retreat of North America's Western Interior Seaway 69 million years ago, which increased the size of the foraging range.
In the time of T. rex, North America presented a natural landscape with some elements that would be familiar to the modern observer and others that were unfamiliar. Leatherback turtles, crocodiles, pike, Esocidae , and pipefish, Lepisosteidae , that lived at that time were quite similar to those found today. Frogs and monitor lizards were other common animals. Ferns, horsetails, palms, magnolias, poplars, and shrubs were some of the dominant plants; the grasses and herbs had already developed, but were not yet widespread. Conifers such as sequoias, araucarias, pines, and cypresses were common. T. rex probably lived in many different habitats due to its wide range, but many of the fossil beds where its skeletons are normally found appear to have been humid subtropical forests. Other inhabitants of the landscape are less familiar and bear no resemblance to today's fauna. Giant pterosaurs, such as Quetzalcoatlus, soared and flew in the skies, with wingspans of more than forty feet. Other theropods, including dromaeosaurids, troodontids, ornithomimids, and cenagnathids, may have been less than four to five meters long. Herds of ceratopsids such as Triceratops and Torosaurus, and hadrosaurids such as Hadrosaurus and Edmontosaurus, roamed the land, while toothed birds flew in the forests and swam the shores of the seas, Hesperornis. Other contemporary herbivorous dinosaurs included the armored Ankylosaurus, the "tough-heads" pachycephalosaurs and Stygimoloch, and small ornithopods such as Thescelosaurus. Mammals, predominantly multituberculates and marsupials, were still small, nocturnal animals that closely resembled today's rats and shrews, such as Ptilodus and Meniscoessus, although there were exceptional genera that seemed already a little older and developed, like Taeniolabis.
Formations
Several notable Tyrannosaurus remains have been found in the Hell Creek Formation. During the Maastrichtian this area was subtropical, with a hot and humid climate. The flora consisted mainly of angiosperms, but also included trees such as redwood, Metasequoia, and araucaria. Tyrannosaurus shared this ecosystem with the ceratopsids Leptoceratops, Torosaurus and Triceratops, the hadrosaurid Edmontosaurus annectens, the parksosaurid Thescelosaurus, the ankylosaurs Ankylosaurus and Denversaurus, the pachycephalosaurs Pachycephalosaurus and Sphaerotholus, and the theropods Ornithomimus, Struthiomimus, Acheroraptor, Dakotaraptor, Pectinodon and Anzu.
Another formation with Tyrannosaurus remains is the Lance Formation of Wyoming. This has been interpreted as a swampy environment similar to today's Gulf Coast. The fauna was very similar to Hell Creek, but with Struthiomimus replacing its relative Ornithomimus. The small ceratopsid Leptoceratops also lived in the area.
In its southern range, Tyrannosaurus lived alongside the jumposaurid Alamosaurus, the ceratopsians Torosaurus, Bravoceratops, and Ojoceratops, hadrosaurs consisting of a species of Edmontosaurus, Kritosaurus, and a possible species of Gryposaurus, the nodosaur Glyptodontopelta, the oviraptorid Ojoraptosaurus, possible species of the theropods Troodon and Richardoestesia, and the pterosaur Quetzalcoatlus. The region is believed to have been dominated by semi-arid interior plains, following the probable retreat of the Western Interior Seaway as global sea level fell.
Tyrannosaurus may also have inhabited Mexico's Lomas Coloradas Formation in Sonora. Although skeletal evidence is lacking, six fallen and broken teeth from the fossil bed have been closely compared to other genera of theropods and appear to be identical to those of Tyrannosaurus. If true, the evidence indicates that the range of Tyrannosaurus was possibly more extensive than previously believed. It is possible that Tyrannosaurus were originally Asian species, which migrated to North America before the end of the Cretaceous period.
Population estimates
Based on studies published in 2021 by Charles Marshall et al., the total population of adult Tyrannosaurus at any given time was perhaps 20,000 individuals, and estimates by computer also suggested a total population of no less than 1,300 and no more than 328,000. The authors themselves suggest that the estimate of 20,000 individuals is probably lower than should be expected, especially when taking into account that disease pandemics could easily end with such a small population. Throughout the existence of the genus, it is estimated that there were around 127,000 generations and that this added a total of approximately 2.5 billion individuals until its extinction.
In the same article, it is suggested that in an adult Tyrannosaurus population of 20,000, the number of individuals living in an area the size of California could be as high as 3,800 animals, while an area the size of Washington DC could support a population of just two Tyrannosaurus adults. The study does not take into account the number of juvenile animals of the genus present in this estimated population due to the fact that they occupy a different niche than adults and therefore the total population is likely to be much larger when this factor is taken into account.. Simultaneously, studies of live carnivores suggest that some predator populations have higher densities than others of similar weight, such as jaguars and hyenas, which are similar in weight but have very different population densities. Ultimately, the study suggests that, in most cases, only one in 80 million Tyrannosaurus would fossilize, while the chances were as high as one in 16,000 that an individual would become fossilized. fossilized in areas that had denser populations.
Meiri, in 2022, questioned the reliability of the estimates, citing uncertainty in metabolic rate, body size, sex- and age-specific survival rates, habitat requirements, and area size variability as shortcomings distribution, which Marshall et al. did not take into account. The authors of the original publication responded that while they agree that the reported uncertainties were probably too small, their framework is flexible enough to accommodate uncertainty in physiology and that their calculations do not depend on short-term changes in population density and geographic range, but rather on their long-term averages. Finally, they comment that they did estimate the range of reasonable survival curves and that they did include uncertainty in the time of onset of sexual maturity and in the growth curve by incorporating uncertainty in maximum body mass.
In popular culture
Since it was first described in 1905, Tyrannosaurus rex has become the most recognized species of dinosaur in popular culture. It is the only dinosaur that is commonly known to the general public by its binomial nomenclature (Tyrannosaurus rex), and its scientific abbreviation T. rex has also found wide use in the English language. Robert Bakker describes this in his book Dinosaur Heresies and explains that a name like Tyrannosaurus rex "it is irresistible to the tongue".
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