Specimens of Tyrannosaurus

Manospondylus: AMNH 3982

The first-named fossil specimen which can be attributed to Tyrannosaurus rex consists of two partial vertebrae (one of which has been lost) found by Edward Drinker Cope in 1892. Cope believed that they belonged to an "agathaumid" (ceratopsid) dinosaur, and named them Manospondylus gigas, meaning "giant porous vertebra" in reference to the numerous openings for blood vessels he found in the bone. The M. gigas remains were later identified as those of a theropod rather than a ceratopsid, and H.F. Osborn recognized the similarity between M. gigas and Tyrannosaurus rex as early as 1917. However, due to the fragmentary nature of the Manospondylus vertebrae, Osborn did not synonymize the two genera.

Dynamosaurus: BMNH R7994

The holotype of Tyrannosaurus rex, a partial skull and skeleton originally called AMNH 973 (AMNH stands for American Museum of Natural History), was discovered in the U.S. state of Montana in 1902 and excavated over the next three years. Another specimen (AMNH 5866), found in Wyoming in 1900, was described in the same paper under the name Dynamosaurus imperiosus. At the time of their initial description and naming, these specimens had not been fully prepared and the type specimen of T. rex had not even been fully recovered. In 1906, after further preparation and examination, Henry Fairfield Osborn recognized both skeletons as belonging to the same species. Because the name Tyrannosaurus rex had appeared just one page earlier than Dynamosaurus in Osborn's 1905 work, it was considered the older name and has been used since. Had it not been for page order, Dynamosaurus would have become the official name.

Holotype: CM 9380

CM 9380 is the type specimen used to describe Tyrannosaurus rex. Fragments of (then) AMNH 973 were first found in 1902 by Barnum Brown, assistant curator of the American Museum of Natural History and a famous paleontologist in his own right. He forwarded news of it to Osborn; it would be three years before they found the rest of it. It has been reconstructed in recent years, it measured an estimated 11.9 meters in length and an estimated weight of 7.4–14.6 metric tonnes, 9.1 metric tonnes being the average estimate in that study, although most earlier studies have suggested lower weight figures. In 1905 when the type was described by Osborn, previous knowledge of dinosaur predators at the time were based on Jurassic carnosaurs, so the short fore-arms of the Tyrannosaurus were treated with extreme caution, with suspicion that bones of a smaller theropod had become jumbled with the remains of the bigger fossil. Following the 1941 entry of the United States into World War II, the holotype was sold to the Carnegie Museum of Natural History in Pittsburgh for protection against possible bombing raids. The specimen, now labeled CM 9380, is still mounted in Pittsburgh, at first with the tail acting as a tripod in the old-fashioned kangaroo pose. It has since received a modernization of its posture (mounted by Phil Fraley and crew) and can now be found balancing with tail outstretched. Along with a more life-like posture, the specimen also now includes a composite reconstruction of the skull by Michael Holland.

AMNH 5027

AMNH 5027 was discovered and excavated in 1908 by Barnum Brown in Montana, and described by Osborn in 1912 and 1916. At the time of discovery, a complete cervical (neck vertebrae) series for Tyrannosaurus was not previously known, so it was this specimen that brought the short, stocky tyrannosaur neck to light. Compared to later specimens (BMNH R7994 and FMNH PR2081, for instance) the cervical series of AMNH 5027 is much more gracile, so with later discoveries the distinction between tyrannosaurid necks and the necks of carnosaurs became more obvious. This specimen also provided the first complete skull of Tyrannosaurus rex. In total, Brown found five partial Tyrannosaurus skeletons.

Famous mount

Osborn planned to mount the similarly-sized AMNH 5027 and AMNH 973 together in dynamic poses. Designed by E.S. Christman, the scene was to depict a rearing Tyrannosaurus (AMNH 5027) snapping at another cowering one (AMNH 973), as they fought over the remains of a hadrosaur, described at the time as Trachodon:

It is early morning along the shore of a Cretaceous lake four million years ago. A herbivorous dinosaur Trachodon venturing from the water for a breakfast of succulent vegetation has been caught and partly devoured by a giant flesh eating Tyrannosaurus. As this monster crouches over the carcass, busy dismembering it, another Tyrannosaurus is attracted to the scene. Approaching, it rises nearly to its full height to grapple the more fortunate hunter and dispute the prey. The crouching figure reluctantly stops eating and accepts the challenge, partly rising to spring on its adversary. The psychological moment of tense inertia before the combat was chosen to best show positions of the limbs and bodies, as well as to picture an incident in the life history of these giant reptiles.

However, technical difficulties prevented the mount from being executed. One obvious problem was that the Cretaceous Dinosaur Hall was too small to accommodate this dramatic display, and AMNH 5027 was already mounted by itself as the central attraction of the hall. The forearms of Tyrannosaurus were not well documented and the hands were unknown, so for the sake of the display, the forearms of AMNH 5027 were given three fingers, based on the forelimbs of Allosaurus (the more allosaur-like arms were replaced several years later when better fossils of tyrannosaurid arms were found).

The mount retained a rearing pose similar to the initial proposal. By the 1980s it was generally accepted that such a pose would have been anatomically impossible in life, and the skeleton was re-mounted in a more accurate, horizontal pose during a renovation of the museum's dinosaur halls in the early 1990s. The mount can still be seen on display on the fourth floor of the American Museum.

In 1960, after the Second World War, the holotype of Dynamosaurus imperiosus (AMNH 5866) and a second specimen (AMNH 5881) were also sold and now reside in the collections of the Natural History Museum, London (formerly the British Museum of Natural History), where they are known as BMNH R7994 and BMNH R7995, respectively. The American Museum of Natural History features AMNH 5027 in its famed Hall of Saurischian Dinosaurs to this day.

Nanotyrannus: CMNH 5741

A small but nearly complete skull of Nanotyrannus lacensis, frequently considered to be a juvenile T. rex, was recovered from Montana in 1942. This skull, Cleveland Museum of Natural History (CMNH) 7541, measures 60 centimeters (2.0 ft) in length and was originally classified as a species of Gorgosaurus (G. lancensis) by Charles W. Gilmore in 1946. In 1988, the specimen was re-described by Robert T. Bakker, Phil Currie, and Michael Williams, then the curator of paleontology at the Cleveland Museum of Natural History, where the original specimen was housed and is now on display. Their initial research indicated that the skull bones were fused, and that it therefore represented an adult specimen. In light of this, Bakker and colleagues assigned the skull to a new genus, named Nanotyrannus for its apparently small adult size. The specimen is estimated to have been around 5.2 metres (17 ft) long when it died. However, a detailed analysis of the specimen by Thomas Carr in 1999 showed that the specimen was, in fact, a juvenile, leading Carr and many other paleontologists to consider it a juvenile specimen of T. rex.

In 2001, a more complete juvenile tyrannosaur (nicknamed "Jane", catalog number BMRP 2002.4.1), belonging to the same species as the original Nanotyrannus specimen, was uncovered. This discovery prompted a conference on tyrannosaurs focused on the issues of Nanotyrannus validity, held 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 the discovery of "Jane" as a confirmation that Nanotyrannus was, in fact, a juvenile T. rex. Peter Larson continued to support the hypothesis that Nanotyrannus lancensis was a separate but closely related species, and also argued that Stygivenator, which is generally considered to be a juvenile of T. rex, could be a younger specimen of Nanotyrannus.

An early suggestion for distinction was based on Nanotyrannus possessing at least two more teeth in both jaws than other specimens referred to Tyrannosaurus, but in his 1999 study of tyrannosaurid growth patterns, Carr showed that in Gorgosaurus libratus, the number of teeth decreased as the animal grew, and he used this data to support the hypothesis that N. lancensis is simply a juvenile T. rex. Tsujihi and colleagues, studying growth in Tarbosaurus bataar, found little to no decrease in tooth count during growth, even though they had juvenile specimens much younger than that of Nanotyrannus. The authors also noted that both Tyrannosaurus and Gorgosaurus show significant differences in tooth count between individuals of the same age group, and that tooth count may vary on an individual basis not related to growth.

Larson has also contended that, along with skull features, Nanotyrannus can also be distinguished from Tyrannosaurus by proportionally larger hands with phalanges on the third metacarpal and in the furcula morphology, as seen in an undescribed specimen. Limb proportion analysis published in 2016 suggested that Nanotyrannus specimens have differing levels of cursoriality, cited as a potential difference between N. lancensis and T. rex. However, paleontologist Manabu Sakomoto has commented that this conclusion may be impacted by low sample size, and the discrepancy does not necessarily reflect taxonomic distinction. In 2013, Carr declared that all of the differences claimed to support Nanotyrannus have turned out to be individually or ontogenetically variable features or products of distortion of the bones. In 2016, Joshua David Schmerge argued for Nanotyrannus' validity based on BMRP 2002.4.1, which he stated has a groove in its dentary bone not seen in T. rex specimens. As that feature is only found in Dryptosaurus and the Albertosaurinae, Schmerge suggested this implies Nanotyrannus is a valid taxon within the Albertosaurinae, based on the groove and other skull features. The same year, Carr and his associates asserted that the presence or absence of a dentary groove did not clarify Nanotyrannus validity or classification, being a common and ontogenetically variable feature among tyrannosauroids.

Joshua David Schmerge proposed in a 2016 paper that Nanotyrannus is a valid genus based off specimen BMRP 2002.4.1, due to its dentary groove which is not seen in known T. rex specimens. Said feature is described as a groove containing pores, on the lateral surface of the dentary bone in theropod dinosaurs. As that feature is only found in Dryptosaurus and the Albertosaurinae, that would imply that Nanotyrannus is a valid taxon nested within the Albertosaurinae, based on the presence of this groove, as well as other features of the skull. In the same year, Carr and his associates wrote a separate paper which claimed that the presence or absence of a dentary groove does not clarify the validity of ‘Nanotyrannus’ or its phylogenetic position among tyrannosauroids as the groove is a widespread feature of tyrannosauroids that is present in T. rex and many other specimens, and that it is an ontogenetically variable feature that changes from a sharp, deeply-impressed groove to a shallower sulcus as an individual matures.

A 2020 study by WHolly oodward and colleagues showed the specimens referred to Nanotyrannus were all ontogenetically immature and found it probable that these specimens belonged to T. rex. Carr studied CMNH 7541 again in a 2020 paper on the growth history of Tyrannosaurus, finding that it fit within the expected ontogenetic variation of the taxon, and even displayed juvenile characteristics found in other specimens. It was classified as a juvenile, under 13 years old with a skull less than 80 cm (31 in), united by 24 changes in the skull with older specimens, all 24 changes only occurring once during ontogeny. No significant sexual or phylogenetic variation was discernible among any of the 44 specimens studied, with Carr stating that characters of phylogenetic importance decrease throughout age at the same rate as growth occurs. Discussing the results of his 2020 study, Carr described how all specimens of "Nanotyrannus" formed a continual growth transition between the smallest juveniles and the subadults, unlike what would be expected if it were a distinct taxon where the specimens would group to the exclusion of Tyrannosaurus. Carr concluded that "the 'nanomorphs' are not all that similar to each other and instead form an important bridge in the growth series of T. rex that captures the beginnings of the profound change from the shallow skull of juveniles to the deep skull that is seen in fully-developed adults."

LACM 23844

In 1966, a crew working for the Natural History Museum of Los Angeles County under the direction of Harley Garbani discovered another T. rex (LACM 23844) which included most of the skull of a very large, mature animal. When it was put on display in Los Angeles, LACM 23844 was the largest T. rex skull on exhibit anywhere. Garbani also discovered several other partial skeletons over the next decade (including LACM 23845, the holotype of "Albertosaurus" megagracilis), some of which are maintained in the collections of the University of California Museum of Paleontology in Berkeley, California. Other skulls and partial skeletons were discovered in South Dakota and Alberta, Canada in the early 1980s.

"Black Beauty": RTMP 81.6.1

Black Beauty (specimen number RTMP 81.6.1) is a well-preserved fossil of Tyrannosaurus rex. The nickname stems from the apparent shiny dark color of the fossil bones, which occurred during fossilization by the presence of minerals in the surrounding rock. The specimen is housed in the Royal Tyrrell Museum in Drumheller, Alberta, Canada. Black Beauty is the 14th-most complete-known skeleton of Tyrannosaurus rex, featuring 85 original bones (28% complete). Casts are on display in museums around the world, like the display at Naturhistoriska Riksmuseet in Stockholm, Sweden. In 2009, a paper by Jack Horner and colleagues illustrated the concept of parasitic infections in dinosaurs by analysing the lesions found on the cranial bones of Black Beauty. The specimen has been used to study comparative morphology between tyrannosaurids and Tyrannosaurus individuals, and some have suggested that Black Beauty should be classed as Dynamosaurus (=Tyrannosaurus). It has been claimed to be the smallest adult T. rex specimen known, even though a number of other adults have skeletal measurements that are similar to or smaller than those of Black Beauty.

Black Beauty was found in 1980 by Jeff Baker, while on a fishing trip with a friend in the region of the Crowsnest Pass, Alberta. A large bone was found in the riverbank and shown to their teacher. Soon afterward, the Royal Tyrrell Museum was contacted, and excavation of the sandstone matrix surrounding the fossils began in 1982.

Replicas of Black Beauty have been shown in some exhibitions and museums, including both simple skull montages and complete skeletons. The Naturhistoriska riksmuseet in Stockholm has a mounted complete skeleton of Black Beauty as one of their primary exhibitions called 4 ½ miljarder år, featuring the history of earth and life. Black Beauty has also been displayed in Paleozoological Museum, and a replica of the skull is on display at the Museum of African Culture. It was also part of the traveling exhibit Dinosaur World Tour in the 1990s.

"Stan": BHI 3033

Stan is the nickname given to a fossil found in Hell Creek Formation, South Dakota, close to Buffalo in 1987 by Stan Sacrison, who also discovered the Tyrannosaurus specimen nicknamed "Duffy". The original fossils are now housed at Black Hills Institute of Geological Research, Inc. center. It is a well known specimen, and one of the most complete, with 199 bones recovered. About 30 casts of the original fossil have been sold worldwide, each for a price of about $100,000. Stan's mount measures 11.8 meters (39 ft) long, while Scott Hartman's restoration yields an 11.3-meter-long estimate. He attributes the difference to the awkward spacing the mounted skeleton shows between its cervical vertebrae and its cranium. There is an extended misconception that Stan is 10.9 meters long, but that was just an (admitted) typo committed by Hartman in one of his works. According to new studies Stan's weight has been estimated between 5.9 metric tons (6.5 short tons) and 10.8 metric tons (11.9 short tons), 8.4 metric tons (9.3 short tons) being the average estimate.

Casts of Stan's skeleton can be found in many displays around the world. A cast can be found at Manchester Museum, and it has also been at The Children's Museum of Indianapolis together with the Tyrannosaurus specimen "Bucky" and the Triceratops "Kelsey", as well as New Mexico Museum of Natural History and Science and Houston Museum of Natural Science. Other casts are located at the National Museum of Natural History, the Rocky Mountain Dinosaur Resource Center, the Oxford University Museum of Natural History, the Natural History Museum in Oslo, the Cerritos Public Library in Cerritos, California, at the Googleplex, the Wyoming Dinosaur Center, and at Dinópolis (Teruel, Spain).

When BBC tested the power of Tyrannosaurus jaws in their program The Truth About Killer Dinosaurs (2005), the hydraulic skull model was based on Stan's skull which measures 1.40 meters long and is the best preserved T rex skull. Gregory Erickson estimated the bite power, and came to the conclusion that Tyrannosaurus would have had a bite force of about 6.8 tonnes, or 60,000 Newtons. Stan has also been used for studies involving restoration of dinosaurs body mass and study on how they could have moved.

Like many other fossils of Tyrannosaurus rex, the skeleton of Stan shows many broken and healed bones. These include broken ribs and damages in the skull. One of the most prominent injuries are in the neck and the skull. A piece of bone is missing at the rear, and the skull also bears a hole 1 inch wide, probably made by another Tyrannosaurus. Also, two of the cervical vertebrae are fused, and another has additional bone growth. This could have been caused by another Tyrannosaurus bite. The bite marks are healed, indicating that Stan survived the wounds. Stan could also have been infected by Trichomonas-like parasites.

"Wankel Rex": MOR 555

In 1988, local rancher Kathy Wankel discovered another Tyrannosaurus rex in Hell Creek sediments on an island in the Charles M. Russell National Wildlife Refuge of Montana. This specimen was excavated by a team from the Museum of the Rockies led by paleontologist Jack Horner, with assistance from the U.S. Army Corps of Engineers. The specimen, given the number MOR 555 but informally called the "Wankel rex," includes approximately 46 percent of the skeleton, including the skull, as well as what at the time was the first complete T. rex forelimb. It has a recently estimated length of around 11.6 meters (38 ft) and a weight between 5.8 metric tons (6.4 short tons) and 10.8 metric tons (11.9 short tons) in newer figures, 8.3 metric tons (9.1 short tons) being the average estimate. It was long on exhibit at the Museum of the Rockies in Bozeman, Montana. Casts of MOR 555 are on display at the National Museum of Scotland, the Australian Fossil and Mineral Museum, and the University of California Museum of Paleontology. A bronze cast of the specimen, known as "Big Mike", stands outside the Museum of the Rockies.

It is estimated that the "Wankel rex" was 18 years old when it died, an adult but not completely grown. The "Wankel rex" was also one of the first fossil dinosaur skeletons studied to see if biological molecules still existed within the fossilized bones. Doctoral candidate Mary Schweitzer found heme, a biological form of iron that makes up hemoglobin (the red pigment in blood).

The Corps of Engineers owns the "Wankel rex", and for years permitted its display at the Museum of the Rockies. In June 2013, the Corps loaned the specimen to the National Museum of Natural History, Smithsonian Institution museum in Washington, D.C. for 50 years. (The Museum of the Rockies continues to display a cast reconstruction of the skull by Michael Holland). The specimen went on temporary display on National Fossil Day, 16 October 2013, and was exhibited until the museum's dinosaur hall exhibit closed for renovation in the spring of 2014. The skeleton will be the centerpiece of the dinosaur hall when it reopens in 2019. (The Museum of the Rockies has about a dozen T. rex skeletons, and mounted an 80-percent-complete specimen (MOR 980) after the "Wankel rex" had been shipped to the Smithsonian.)

Museum of the Rockies also houses a large Tyrannosaurus rex skull catalogued as MOR 008. The skull bones were found and collected in the 1960s near Billings, Montana, and the skull was reconstructed by Michael Holland and put on display in 2006. The skull is about 1.4 meters long.

"Sue": FMNH PR2081

Susan Hendrickson of the Black Hills Institute discovered the best-preserved Tyrannosaurus currently known, in the Hell Creek Formation near Faith, South Dakota, on 12 August 1990. This specimen, named "Sue" in honor of its discoverer, soon became embroiled in a legal battle over its ownership. The land on which the fossil was discovered was found to lie within the Cheyenne River Indian Reservation and is occupied by the family of Maurice Williams, a Native American of the Sioux tribe. In 1992, Williams claimed he still owned the fossil, for which the Black Hills Institute had paid him US$5,000. The local Cheyenne River Sioux Tribe, of which Williams is a member, also claimed ownership. The fossil, as well as many thousands of pages of field notes and business records, were confiscated by the Federal Bureau of Investigation in 1992 and held throughout the ensuing court proceedings. In 1997, the suit was settled in favor of Maurice Williams because his land is technically held in trust for him by the United States government. Therefore, although the Black Hills Institute had paid Williams for the fossil, it was judged that the fossil could be considered "land" which Williams owned but could not legally sell without government permission. The fossil was returned to Williams' ownership and Pete Larson, vice-president of the Black Hills Institute, was sentenced to two years in federal prison for an unrelated customs violation discovered by the FBI while searching through his business records. Williams quickly offered up "Sue" for auction by Sotheby's in New York, where it was sold to the Field Museum of Natural History in Chicago for US$8.4 million—the highest price ever paid for a fossil.

Preparation of "Sue" (FMNH PR2081) was completed at the Field Museum and the skeleton was placed on exhibit on 17 May 2000. A replica of Sue is on exhibit at Disney's Animal Kingdom in Walt Disney World.

About 90% of the skeleton was recovered, allowing the first complete description of a Tyrannosaurus rex skeleton.

Sue has a length of 12.3 meters (40 ft), stands 3.73 m (12.2 ft) tall at the hips, and according to the most recent studies estimated to have weighed between 8.4 and 14 metric tons when alive. In one of these studies, estimations by Hutchinson et al. (2011) point out to a figure of 14 metric tonnes being the average estimate. Authors have stated that their upper and lower estimates were based on models with wide error bars and that they "consider to be too skinny, too fat, or too disproportionate". Historically older estimations have produced figures as low as 5.7–6.4 metric tonnes for this specimen.

It has been hypothesised that Sue's impressive size may have been achieved due to a prolonged ontogenic development, since it is the third oldest Tyrannosaurus known. Sue's age at the time of death was estimated by Peter Mackovicky and the University of Florida to be 28 years old, over 6–10 years older than most big Tyrannosaurus specimens, like MOR 555, AMNH 5027 or BHI 3033. The only known specimens of T. rex that are older than Sue are Trix, whose age at the time of death is estimated as a minimum of 30 years, and Scotty, which had been confirmed older than Trix and Sue (estimated to be in its early thirties at the time of its death), while also being reported to being longer at 13 m (43 ft) and more massive.

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Peck's Rex (also known as "Peckrex", "Rigby's rex" and Tyrannosaurus "imperator") is the nickname given to a fossil specimen found in Montana in 1997. The discovery was made by Louis E. Tremblay on 4 July 1997 working under the supervision of J. Keith Rigby Jr. who led the excavation and bone preparation.

The fossil got its nickname after Fort Peck, which is located close to the place of discovery. Peck's Rex has been part of several exhibitions on dinosaurs, and is specifically famous because it was the first specimen of its species to have Metacarpal III preserved.

The fossil of Peck's Rex is relatively well preserved. The skeleton includes a relatively complete skull with jaws, multiple vertebrae of the back and tail, a well preserved gastralium, and hipbone with complete ischium and pubis. The left hindleg is relatively complete with a 1.2-meter-long (3.9 ft) femur, missing only some toe bones. The forelimbs include the scapula and furcula, both humeri and right hand phalanges, as well as metacarpal III. Because the skeleton is of the gracile morphotype, Peck's Rex is believed to be a male, although the hypothesis which suggests that the sex of Tyrannosaurus specimens can be determined by the degree of skeletal sturdiness has been debated in recent years. Peck's Rex has been the subject of research regarding parasitic infections in dinosaurs. The forelimbs of Peck's Rex have also been studied as they show evidence of use. This evidence includes the construction of metacarpal III, as well as repeated fractures in the furcula—possibly caused by heavy loads or pressure (Carpenter and Lipkin, 2005).

Casts of Peck's Rex have been featured at several museums including the Maryland Science Center, the Fort Peck Interpretive Center and Museum (beside a lifesized model), and the Carnegie Museum of Natural History as part of the exhibit: Dinosaurs in Their Time where it is mounted in a "face off" position against the holotype Tyrannosaurus skeleton (CM 9380). Cast pieces and skeletons of Peck's rex (like forelimbs, teeth, and parts of the jaws and feet) are also for sale. Peck's Rex real fossilized bones are exhibited at The Museum of the Rockies as part of a full body mount completed with plaster replacing the missing bones, and was nicknamed Montana's Rex. This was made since their old main T rex's complete real skeleton; Wankel Rex (now nicknamed Nation's Rex) was sent to Washington DC Smithsonian's museum to occupy a central part in the museum's dinosaur hall, featuring a dynamic mount showing the apex predator devouring a triceratops carcass. It has been stated by Pete Makovicky, the Chicago museum’s lead curator of dinosaurs, that this specimen is in the same size range as "Sue" and "Scotty".

"Bucky": TCM 2001.90.1

Bucky is a fossil of a juvenile specimen that was located at the College of Charleston's Addlestone Library in Charleston, South Carolina, United States until May 1, 2018. Some paleontologists suggest that female T. rex were of the robust morphotype, which includes Bucky, but this method for distinguishing gender is not universally accepted. It is the first juvenile Tyrannosaurus ever placed on permanent exhibit in a museum.

Bucky has a bird-like skeletal structure, as it is one of the few dinosaur fossils found with a furcula. A furcula, or fused clavicles, is a boomerang shaped "wishbone" that would measure 29 centimeters (11 in) wide and 14 cm (5.5 in) high. Bucky's furcula is the first one found for the genus Tyrannosaurus. The furcula is thought to be a link between dinosaurs and birds and is the center of debate surrounding the origin of birds. Bucky also has a nearly complete set of gastralia, or belly ribs, and an ulna, or lower arm bone. As of now, 101 bones, or about 34% of Bucky's skeleton, has been discovered and verified. Bucky is the sixth-most complete Tyrannosaurus rex out of more than 40 that have been discovered. Bucky's tail is the third-most complete tail of any Tyrannosaurus rex known and has a nearly complete vertebral column to the end of the pelvis. Bucky's skull is a reconstruction which utilized modified casts of other Tyrannosaurus rex specimens.

Bucky is now displayed in The Children's Museum of Indianapolis. Found in Dinosphere, Bucky is displayed along with Stan, an adult Tyrannosaurus, in a hunting scene. Both dinosaurs are attacking Kelsey the Triceratops. Bucky attacks Kelsey from behind, while Stan acts as a diversion in front of the triceratops. The end of the fight is left ambiguous. Bucky is displayed with a full set of gastralia, which is unusual. But because Bucky was discovered with a full set, it is displayed along with it.

The dinosaur remains were found in 1998 in the Hell Creek Formation near the town of Faith, South Dakota. The skeleton, transported by water, ended up in a low shallow valley along with bones from an Edmontosaurus and Triceratops. It was discovered by rancher and cowboy Bucky Derflinger. The excavation site was 150 by 30 feet (45.7 m × 9.1 m), about 4,500 square feet (420 m²). Bucky was well preserved and easily prepared by the Black Hills Institute in South Dakota. Excavation and preparation of Bucky was relatively easy because the surrounding rock matrix was soft.

Bucky Derflinger found Bucky's skeleton in 1998 when he was 20 years old. He was a rancher and a rodeo cowboy. While breaking in a young horse on his father's ranch, Derflinger discovered a pes phalange, or toe bone, from Bucky's skeleton. He has also discovered another Tyrannosaurus and a slew of remains of duck-billed dinosaurs on his father's land. Derflinger is the youngest person to discover a Tyrannosaurus. He has been collecting dinosaur fossils since he was eight years old.

"Jane": BMRP 2002.4.1

Jane is a fossil specimen of small tyrannosaurid dinosaur (Nanotyrannus lancensis or a juvenile Tyrannosaurus), officially known as BMRP 2002.4.1, discovered in the Hell Creek Formation in southern Montana in 2001.

After four years of preparation, Jane was put on display at Rockford, Illinois' Burpee Museum of Natural History as the centerpiece of an exhibit called "Jane: Diary of a Dinosaur." Paleontologists who support the theory that Jane represents a juvenile believe the tyrannosaur was approximately 11 years old at its time of death, and its fully restored skeleton measured 6.5 meters (21 ft) long, a bit more than half as long as the largest-known complete T. rex specimen, nicknamed "Sue," which measures 12.3 m (40 ft) long. According to Hutchinson et al. (2011), the weight of the Jane specimen in life was probably between 639 kg (1,409 lb) and 1,269 kg (2,798 lb), 954 kg (2,103 lb) being the average estimate. Its large feet and long legs indicate it was built for speed and could possibly run as fast as 20–30 miles per hour. Its lower jaw has 17 curved, serrated teeth.

Despite having a typically female name, Jane's sex is unknown—the specimen was named after Burpee Museum benefactor Jane Solem. The specimen was found in the summer of 2001 by Carol Tuck and Bill Harrison on an expedition led by Burpee Museum curator Michael Henderson.

The Jane specimen has been central to the debate regarding the validity of the proposed tyrannosaurid genus Nanotyrannus. Jane's skull is nearly identical to the skull of the original Nanotyrannus specimen, confirming that they belong to the same species. A conference was held at the Burpee museum in 2005, during which paleontologists debated whether these "pygmy tyrants" represented adult specimens of a small species, or juvenile specimens of Tyrannosaurus rex. While there were a few dissenters, a majority of paleontologists at the conference decided on the latter, and that both Jane and Nanotyrannus were juvenile T. rex. However, the Jane material has yet to be properly studied and described by scientists. Although Larson (2013) saw Jane as more identical to CMNH 7541 and LACM 28471 than to adult T. rex in having a higher tooth count, large pneumatic foramen on the center of the quadratojugal, T-shaped postorbital, and fused shoulder blade and pelvis, Yun (2015) concurred with the opinion of most workers that Nanotyrannus is a juvenile T. rex, noting that a juvenile specimen of Tarbosaurus described by Tsuihiji et al. (2011) also has a T-shaped postorbital.

"B-rex": MOR 1125

This specimen was found in the lower portion of the Hell Creek Formation near Fort Peck Lake in the Charles M. Russell National Wildlife Refuge in Garfield County, Montana. Its discoverer was Bob Harmon, a fossil preparator for the Museum of the Rockies, and was nicknamed the "B-rex" (or "Bob-rex") in honor of Harmon. The specimen was discovered in 2000, and excavated by MOR from 2001 to 2003. Although only 37 percent of the skeleton was present, this included almost all of the skull (although the skull was nearly completely disarticulated). A cast reconstruction of the skull by Michael Holland is displayed at Museum of the Rockies. The specimen also includes several cervical, dorsal, sacral, and caudal vertebrae; several chevrons; some cervical and dorsal ribs; left scapula and coracoid; the furcula; the left ulna; both femora, tibiae, and ulnae; the right calcaneum; right astragalus; and a number of pes phalanges.

In the March 2005 Science magazine, Mary Higby Schweitzer of North Carolina State University and colleagues announced the recovery of soft tissue from the marrow cavity of a fossilized leg bone (a 1.15-m-long femur), from a 68-million-year-old Tyrannosaurus. The bone had been intentionally, though reluctantly, broken for shipping and then not preserved in the normal manner, specifically because Schweitzer was hoping to test it for soft tissue. Designated MOR 1125 (and known informally as B-rex), the dinosaur had been excavated from the Hell Creek Formation. Flexible, bifurcating blood vessels and fibrous but elastic bone matrix tissue were recognized. In addition, microstructures resembling blood cells were found inside the matrix and vessels. The structures bear resemblance to ostrich blood cells and vessels. However, since an unknown process distinct from normal fossilization seems to have preserved the material, the researchers are being careful not to claim that it is original material from the dinosaur. If it is found to be original material, any surviving proteins may be used as a means of indirectly guessing some of the DNA content of the dinosaurs involved, because each protein is typically created by a specific gene. The absence of previous finds may merely be the result of assumptions that soft tissue could not be preserved, so that nobody had looked for it. Since the first, two more tyrannosaurs and a hadrosaur have also been found to have such tissue-like structures.

Paleontologist Thomas Kaye of the University of Washington in Seattle has also hypothesized that the soft-tissue is permineralized biofilm created by bacteria while digesting and breaking down the original specimen. He has discovered this to be true in many specimens from the same area.

In 2016, it was finally confirmed by Mary Higby Schweitzer and Lindsay Zanno et al that the soft tissue was medullary bone tissue, like that in modern birds when they are readying to lay eggs. This also confirmed the identity of the Tyrannosaurus MOR 1125 as a female.

"Samson"

Following the sale of "Sue," another Tyrannosaurus rex skeleton was, under the individual name of "Z-rex", put up for auction on eBay in 2000 with an asking price of over US$8 million. It failed to sell online but was purchased for an undisclosed price in 2001 by British millionaire Graham Ferguson Lacey, who renamed the skeleton "Samson" after the Biblical figure of the same name.

This specimen, discovered on private land in Harding County, South Dakota in 1981 by Michael Zimmerschied, and Dee Zimmerschied and on 4 October 1992 (Alan and Robert Detrich re-discovered Samson after it was originally found and deemed by paleontologists that several bones had washed in and there was nothing left). It was shortly after that when Fred Nuss and Candace Nuss of Nuss Fossils with the Detrich brothers found the most complete and undistorted Tyrannosaurus rex skull ever discovered, which was prepared by the Carnegie Museum starting in May 2004. After preparation was complete in March 2006, the specimen was returned to its owner, who plans to put it on an educational tour.

"Samson" along with some other dinosaur skeletons was sold at auction on 3 October 2009, exhibited in early 2011 at the Embedded Systems Conference Silicon Valley.

Samson measured 11.9 m (39 ft), only slightly shorter than Sue.

"Baby Bob"

On 7 July 2013, fossil hunter Robert Detrich of Wichita, Kansas, unearthed the remains of what is believed to be a 4-year-old Tyrannosaurus rex. Detrich unearthed the fossil dubbed "Baby Bob" in a fossil-rich area near the Eastern Montana town of Jordan. Its femur measures about 25 inches, and if all the preliminary data pans out, that would make it among the smallest T.rex specimens ever found. "This is the discovery everyone wishes and longs for", Detrich said. Detrich has been sharing his findings with other researchers, including the Smithsonian Institution.

Scientists are eager to learn more about the years before the carnivore reached its full size of about 40 feet from head to toe. Detrich estimates that Baby Bob was about half that size. "We hardly know anything about how T.rex grew up," said Thomas Carr, director of the Carthage Institute of Paleontology at Carthage College in Kenosha, Wis. "We really only have a handful of fossils of sub-adults and juveniles, so any additional fossils that can fill in that early end of the growth period is scientifically very important because most of the skeletons of rex that we have are from adults." Bob Bakker, curator of paleontology at the Houston Museum of Natural Science, said the scarcity of half-grown T. rex fossils has raised questions. Young T. rex may have stayed in the nest until they were almost grown, he said. "If this is a really good genuine baby T.rex, it could tell us whether it was fit to hunt on its own or whether it looks like it was designed to wait for mom and dad to come back," Bakker said. Another fossil, first described and named as Nanotyrannus lancensis in 1946, also raises questions about whether or not it is a closely related tyrannosaur species or a juvenile Tyrannosaurus.

Bakker is among those certain there are two species, while Carr is part of another group that believes suspected Nanotyrannus fossils are actually juvenile T. rex remains. Another juvenile T. rex would give scientists something to use for comparison purposes. Baby Bob has been fully excavated, although it will take another year to clean. Detrich said the skull, which is about 75 percent complete, and most of the major skeletal elements were found strewn across a flood plain, although very few vertebra and ribs were found. "This is so exciting," Detrich said. "I can't even tell you the importance of this dinosaur." As a commercial fossil hunter, Detrich eventually plans to sell the fossil. He said most of his fossil finds have found homes in museums. He's hopeful the same will happen to Baby Bob.

"Scotty": RSM P2523.8

"Scotty" is the nickname for the Tyrannosaurus rex fossil, cataloged as RSM P2523.8, that was discovered in Saskatchewan, Canada in 1991. Since its discovery and extensive subsequent study, "Scotty" has been referred to as the largest T. rex ever discovered in the world, the largest of any dinosaur discovered in Canada, and as one of the oldest and most complete fossils of its kind at more than 70% bulk. "Scotty" resides at the Royal Saskatchewan Museum's T. rex Discovery Centre in Eastend, SK, Canada. In May 2019, a second mount was erected at the Royal Saskatchewan Museum in Regina, where the exhibit reflects the recent discoveries about the fossil.

"Scotty" was discovered by Robert Gebhardt, a high school principal from Eastend, SK who accompanied palaeontologists from the Royal Saskatchewan Museum on a prospective expedition into the Frenchman Formation in southwestern Saskatchewan on August 16, 1991. Although he was only there to learn how to find and identify fossils, Gebhardt uncovered a tooth and tail vertebra that the museum was able to verify belonged to a T. rex. Initially, Gebhardt thought that the visible fossil was actually ironstone. It wasn't until June 1994 that the Royal Saskatchewan Museum was able to begin the excavation, which was led and overseen by the Museum's Ron Borden, as well as resident paleontologists Tim Tokaryk and John Storer who were with Gebhardt when he uncovered the first fossils. The bones were deeply packed in dense, iron-laden sandstone, which took more than twenty years for the team to fully remove, excavate, and assemble the majority of the skeleton, with additional trips being made to the site to retrieve smaller bones and teeth. The entire process of excavating the skeleton was also slowed down by its considerable size. The first fossils unearthed were part of the upper body, specifically vertebra, parts of the jaw, and teeth. At the time of its discovery, the fossil was one of only 12 known T. rex skeletons of significant completion. The name "Scotty" came from the celebratory bottle of scotch shared by the team that had discovered and identified the bones.

In 2010, the University of Alberta Department of Biological Sciences' Scott Pearson began work on a research project that sought to compare the sizes of known T. rex fossils. His findings, published in 2019, yielded that "Scotty" is the largest (in weight and length), having out-measured the previous largest known Tyrannosaurus rex: SUE of the Chicago Field Museum (FMNH 2081). After prolonged study of the growth patterns in the bones, "Scotty" was also declared as one of the oldest known T. rex fossils at 30 years old. The specimen known as "Trix" is also estimated to have been 30 years old upon its death.

"Scotty" is reported to be 13 meters (43 feet) long and weighed an estimated 8.8 tonnes (8870 kg). Despite it not being a complete fossil, paleontologists were able to create the estimation for the weight and length through measurements of important weight bearing bones such as the femur, hip, and shoulder bones that have all been measured to be larger and thicker with "Scotty" than the corresponding bones with "Sue". Going from the latest study "Scotty" exceeds "Sue" in 84.6% of the published measurements. "Scotty" has a larger hip girdle than "Sue" its femur is also longer and wider than "Sues" at 133 cm and has a circumference of 590 mm while the specimen "Sue" has a femur length of 132 cm and a circumference of 580 mm. The projected weight was calculated by analyzing how much weight the leg bones would have been able to support. The fossil is dated at around 68 million years. Scientists are unsure if "Scotty" was male or female, which is not unusual for a T. rex specimen.

Both specimens "Sue" and "Scotty" had their weights estimated in the latest study. The method used to calculate the mass in the latest study was the same for both of the specimens and the data shows that Scotty is heavier than Sue is. The latest study put "Scotty's" weight at an estimated 8870 kg(9.7 tons)while "Sue" is estimated at 8462 kg(9.3 tons) Sue has had similar results made on its weight in the past such as Scott Hartmans result of 8400 kg(9.2 tons) obtained through GDI analysis. This is also not the first time that "Scotty" has been estimated to out mass the specimen "Sue". A study conducted back in 2014 that estimated the weight for some of the large theropod dinosaurs and both "Sue" and "Scotty" were included. This older study concluded that "Sue" was around 7377 kg (8.1 tons) with a weight range of 5531 kg(6 tons) to 9224 kg(10 tons) while "Scotty" was heavier at 8004 kg (8.8 tons) with a weight range of 6000 kg(6.6 tons) to 10007 kg(11 tons)

While the reported measurements and weight for "Scotty" are larger than those of “Sue”, some scientists posit that the two fossils are too close in size to officially declare "Scotty" the largest. Evolutionary expert John Hutchinson of the University of London's Royal Veterinary College has stated that the 5% margin separating SUE and "Scotty" is too close to rule out any error and that the difference most likely came down to inches and ounces, rather than the reported feet. The method that was used to calculate its size is not exact and remains another point of contention for the fossil's titles. This could have resulted in Pearson and his team overestimating "Scotty"'s size. The Chicago Field Museum's resident paleontologist and curator of dinosaurs, Pete Macovicky, has stated that he believes "Scotty" and SUE are "statistically indistinguishable". Nonetheless, "Scotty" has presented scientists with new possibilities for the size and age that T. rex could have grown to.

Like other T. rex fossils, "Scotty" shows signs of trichomoniasis, a parasitic infection in the jaw that left visible holes in the bone and was unique to this specific species of dinosaur. Additionally, a broken and healed rib on its right side, broken tail vertebra, as well as a hole near the eye socket are possibly the result of another T. rex attack. Other abnormalities, such as impacted teeth, suggest that "Scotty" was not only bitten, but also bit other animals.

"Tristan"

Commercial paleontologist Craig Pfister discovered the specimen in the lower Hell Creek Formation in Carter County, Montana, in 2010. Its excavation and preservation lasted four years. It was later sold to Danish-born investment banker Niels Nielsen, who loaned the specimen to the Museum für Naturkunde in Berlin, Germany, for research and exhibition. It has been on display at Museum für Naturkunde between 2015 to 2020, moving to the Natural History Museum of Denmark for one year, and expected back in 2021. Nielsen and his friend Jens Jensen named the specimen Tristan-Otto (short: Tristan) for their sons. The Naturkundemuseum Berlin lists it under specimen number MB.R.91216. Several European museums have Tyrannosaurus casts (replicas) or parts, but Tristan is one of only two original skeletons on display in the continent (the other is "Trix" in the Netherlands). The matte-black fossilised skeleton is about 12 m (39 ft) long and 3.4 m (11 ft) tall at the hips. Tristan is among the most complete known Tyrannosaurus skeletons: It was re-assembled from about 300 separate parts, 170 of which are original (including 98% of the skull and all the teeth), the rest reproductions. It is estimated to have died when about 20 years old and it was in poor health, having several bone fractures, bite marks to the skull and signs of disease in the jaw.

"Thomas"

From 2003 to 2005, Thomas was excavated by NHMLA paleontologists in southeastern Montana. At 17 years old, 34 ft (10 m) long and nearly 7,000 lb (3,200 kg), it is estimated to be a 70% complete specimen. Thomas is mounted in a "growth series" with the youngest-known Tyrannosaurus rex fossil, a two-year old, 11-foot-long (3.4 m) specimen, and a 13-year-old, 20-foot-long (6.1 m) juvenile specimen.

This fossil is one of the geologically youngest T. rex specimens known, discovered very near the Cretaceous–Tertiary boundary.

"Ivan"

Ivan is a 65% complete T-rex displayed at the Museum of World Treasures in Wichita, Kansas. The specimen has the most complete tail of any T-rex, only missing around 3 vertebrae. Ivan is around 40 ft long and 12 feet high.

"Trix": RGM 792.000

In 2013, a team of paleontologists from the Naturalis Biodiversity Center (Leiden, Netherlands) traveled to Montana where they discovered and unearthed a large and remarkably complete Tyrannosaurus rex specimen that lived 66 million years ago. Black Hills institute collaborated with the team in the excavation. The bones were cleaned and assembled in a mount at Black Hills Institute's installations, with the help of both Chicago's Field Museum of Natural History and the Naturalis Leiden Museum. Chicago's Field museum sent digital models of their famous specimen, FMNH PR 2081 (Sue) to complete the cast and Naturalis museum replicated the bones using 3D-printing technology.

The specimen was named Trix after former Netherlands' Queen Beatrix. At arrival in the Netherlands, it started touring on public display in an itinerant exhibition titled T. rex in Town. The first exhibit spanned from 10 September 2016 to 5 June 2017 and was set at the only room of the Naturalis museum open to public at the time (the 17th-century building known as Pesthuis), due to the fact that the museum was undergoing restoration. When the Netherlands exhibition ended, it continued travelling through other European countries in 2017, 2018 and 2019. As of August 2019, Trix was returned to display at the Naturalis museum where it is installed in a special room that was under construction during Trix's European tour.

According to Peter Larson, director of Black Hills Institute, Trix is among the most complete Tyrannosaurus found. Between 75% and 80% of its skeletal volume was recovered.

Trix's age has been estimated by counting the growth lines in the bones. Two different methods were used for this: An x-ray microtomography, which can be done without damaging the bones, and a small hole drilled in the fibula to allow comparison with the results of the x-ray-based technique. The growth lines were numerous, and difficult to distinguish. These facts alongside the roughness and rugosity of the skull are indications that this individual had reached an old age for a T. rex; in this case at least thirty years, as opposed to Sue's 28 years old (Sue was the oldest T. rex found before Trix's discovery), making Trix the oldest Tyrannosaurus known along with Scotty.

"Tufts-Love": UWBM 99000

In 2016 Greg Wilson, David DeMar, and a paleontology team from the Burke Museum of Natural History and Culture, the University of Washington, and the Dig Field school excavated the partial remains of a Tyrannosaurus rex from Montana. The partial skeleton was found by two Burke Museum volunteers, Jason Love and Luke Tufts, and was named the "Tufts-Love" rex.

Paleontologists at the Burke Museum believe that the Tufts-Love rex was around 15 years old when it died. The skull is of average size for an adult T. rex. The specimen was found in Late Cretaceous deposits and it is estimated to be 66.3 million years old.

The Tufts-Love rex is undergoing preparation by Michael Holland and his team at the Burke Museum. The skeleton is estimated to be 30% complete, but it includes a complete (all of the bones of the skull and jaws are preserved) and mostly articulated skull. Holland describes the skull as minimally distorted and in an "exquisite" state of preservation.