A current depiction of an adult Tyrannosarurus rex
MEET THE TYRANT LIZARDS!
When you say the word dinosaur to the average person, he might mention one of those big, lumbering herbivores like Brontosaurus or the slightly smaller Hadrosaurs (a.k.a “Duck Billed Dinosaurs”). She might even talk about Triceratops with its prominent horns or the Stegosaurs with their strange spinal “fins.” But ask anyone, and the most frequently mentioned name is Tyrannosaurus rex.
And with good reason. Thanks in great part to the six films in the Jurassic Park and Jurassic World franchises not to mention the numerous Walking With Dinosaur “documentaries” of the 90’s and early 2000’s, many hundreds of millions of people across the globe have an image of the fleet-footed, roaring beast that relentlessly hunts its victims--there’s simply no escaping this nine-ton monster with the steak-knife teeth.
While much of what we hear and see in the lore about T. rex is based on a certain amount of factual evidence, there’s a great deal that’s either wrong (in the case of the Hollywood movies) or missing (in the BBC and Discovery Channel shows)--including the fact that T. rex sported primitive feathers and had anatomical features that we now associate with birds such as a three-toed foot like a vulture or hawk, “hollow” bones, and a wishbone. Further, this remarkable beast was only one member--and one of the last--of a fairly extended family of Tyrannosaurs (the Tyrannosauroidea) that includes smaller dinosaurs like Guanlong and Dilong who thrived millions of years before T. rex. as well as its nearly contemporary smaller 2-ton cousin Albertosaurus.
Have fun exploring the many links on this page. I've provided a biography of Barnum Brown, the man who discovered T. rex as well as materials about the geography and geology of the planet during the 100 million year history of the Tyrannosaurs. Then you'll discover background articles and artists' illustrations that will give you a sense of the current state of research regarding this most remarkable beast and its always fascinating relatives.
Born in 1873 to a hard-working farming family, Barnum Brown had to wait several days for a name while his parents and siblings quibbled over what to call him. Consumed with excitement over the traveling circus show, his older brother suggested naming the baby boy after the illustrious P.T. Barnum. The decision proved prophetic. Brown enjoyed a spectacularly successful 66-year career in paleontology, including his post as curator for the American Museum of Natural History, where he was largely responsible for the museum's multi-ton collection of dinosaur fossils.
Brown's parents wanted to give their son a good education, and they sent him to high school (not available everywhere) in the nearby town of Carbondale, Kansas. After high school, he attended Kansas University and in 1894, he began hunting fossils under the direction of paleontologist Samuel Wendell Williston. The following year, he worked with Williston again, to retrieve a Triceratops skull from Wyoming. Williston wrote of Brown: Brown has been with me on two expeditions and is the best man in the field that I ever had. He is very energetic, has great powers of endurance, walking thirty miles a day without fatigue, is very methodical in all his habits, and thoroughly honest. He has good ability as a student also and has been a student with me in anatomy, geology and paleontology. He practically relieved me of all care in my last expedition.
A recommendation from Williston secured Brown a spot on a fossil dig operated by the American Museum of Natural History. Fine fieldwork for AMNH later earned Brown a job with the museum, and the eager young man left the University of Kansas even before the current academic term was done. The move was vintage Brown; fieldwork always took precedence. In New York, Henry Fairfield Osborn pulled strings to provide Brown with admission and even a scholarship to Columbia University, but Brown's academic abilities didn't match his skills in the field. He didn't last at Columbia and took a decade to complete his undergraduate degree from KU. Decades later, he received an honorary doctorate from Lehigh University, finally enjoying the title of "doctor."
In 1897, while working at AMNH, Brown explored Upper Jurassic beds in Wyoming. At first, the quarry looked empty, but he kept looking. The quarry that initially seemed useless eventually yielded 65 tons of fossils. About the same time, Brown and his colleague Henry Fairfield Osborn asked a Wyoming shepherd if he knew of any fossils in the area. He didn't. Then they realized his stone cabin was made of fossils. The whole cabin.
Back in New York in December 1898, Brown walked to work through the snow one morning, probably expecting a day like any other. That evening, he was on a ship bound for Patagonia, where he spent roughly 18 months digging fossils and braving blizzards. A few years later, he was again unearthing bones in the western United States.
Quarry No. 1 contains the femur, pubes, humerus, three vertebrae and two undetermined bones of a large Carnivorous Dinosaur not described by Marsh. . . . I have never seen anything like it from the Cretaceous. These bones are imbedded in flint-like sandstone concretions and require a great deal of labor to extract. So wrote Brown from Hell Creek, Montana, with an apparent gift for understatement. The "large Carnivorous Dinosaur" was Tyrannosaurus rex, "King of the tyrant lizards." He discovered the first skeleton in 1902 and found a better-preserved skeleton in 1908. Both skeletons were put on display at AMNH. During World War II, Americans feared that the Germans might bomb New York and the T. rex fossil might be lost (not a misplaced fear — many fossils in European museums were blown to bits in the 1940s). The skeleton Brown discovered in 1902 was shipped to the Carnegie Museum in Pittsburgh.
Several years after the initial T. rex discovery, while Barnum Brown was still basking in the glow of accomplishment, tragedy struck. His wife Marion — arguably the love of Brown's life — contracted scarlet fever and died. Their baby daughter Frances contracted the illness at the same time, and managed to survive, but the distraught Brown wasn't up to being a single dad. Following common convention of the time, he turned over his toddler daughter to her mother's parents. They wanted to raise the little girl, and Barnum wanted to bury himself in his work. The iconic photograph of Brown in a natty suit and beaverskin coat might suggest a carefree bachelor, but in reality, it shows a widower. Devoted as he had been to his first wife, however, Brown retained an eye for the ladies. Rumors flew for years about his various exploits, but Brown was discreet, and few rumors were ever confirmed.
Frances didn't see her father much growing up, in particular during a five-year stretch when he was overseas, working in far-flung locales like Samos, Pakistan, India, Burma and Abyssinia. In the years before air travel, quick visits home were unrealistic. Brown's colleagues at AMNH would hear nothing from him for months, but his long absences were punctuated by the delivery of (literal) tons of fossils. In fact, such gargantuan deliveries sometimes served as the only evidence that the fossil hunter was still alive. Friends and family members in the states had reason to worry. In Mandalay, Brown nearly died of malaria, and he was nursed back from the brink by something else he collected: his second wife, Lilian. Fourteen years Brown's junior, flirtatious Lilian tolerated his occasional dalliances, in part because she indulged in one or two of her own.
Brown's extensive overseas fieldwork proved useful in a surprising way years later. During World War II, after he had been required (over his objections) to retire from AMNH, Brown went to work for the war effort in Washington, D.C., providing intelligence on various localities of interest to the U.S. military. His daughter Frances was working in Washington at the same time, so father and daughter lived under the same roof for the first time since she had been tiny. Aside from Frances's fears that her dad was smitten with a Nazi spy, the living arrangement went smoothly.
The Great Depression hurt museum budgets as much as anything else, and to keep excavating, Brown had to be creative. On one trip to the field, he and his wife dropped by the Chicago World's Fair, taking in "The World a Million Years Ago." Never mind that the exhibit put prehistoric humans together with dinosaurs that didn't walk the Earth at the same time, it was a fun show. And it was funded by Sinclair Oil. He eventually made a deal with the Sinclair Oil Company: He reviewed dinosaur booklets for them and they paid for his expeditions. So the gas stations with the Diplodocus logo attracted even more customers by giving them the booklets in the 1930s and 1940s. Brown also provided input for the dinosaur sequence in Fantasia.
It was also during the Great Depression that Brown took on an assistant: Roland Bird. An excellent fossil hunter in his own right, Bird found some of North America's best dinosaur trackways, including extensive track systems near the Purgatoire River in southeastern Colorado, and the Paluxy River limestone beds near Glen Rose, Texas.
Before his career was over, Brown managed to make a remarkable contribution to the field of anthropology, but only after marginal involvement with a gaffe. In the early 1920s, Brown's mentor Osborn was excited by the find of a tooth in Nebraska, later dubbed Hesperopithecus and nicknamed Nebraska Man. The tooth looked like it might belong to a primate. Brown evidently accepted this interpretation at the beginning, but doubts began to gnaw at him. He confided to a colleague that the primate might just as easily be a peccary, which ultimately proved to be the case. But in 1927, Brown reported more welcome news when he confirmed the identification, by Jesse Dade Figgins, of a prehistoric spear point in Folsom, New Mexico. The Folsom point provided evidence that humans were in North America at the end of the Pleistocene Ice Age, and they were hunting big game.
After he retired from AMNH in 1942, Brown continued to lead tours there, often describing the dinosaur fossils he had collected as his "children." One of his last assignments was to supervise the construction of Sinclair's life-sized dinosaur models for the 1964 World's Fair. Brown completed his task but didn't live long enough to see the dinosaurs' trip to the fair. About a year after he died, the lovable giants rode on a barge from their construction site in the town of Hudson, floating down the Hudson River. Brown, who had died in February 1963, just a week shy of his 90th birthday, never got to see the looks on Manhattanites' faces. (c) WWW. STRANGE SCIENCE.NET Retrieved 22 March 2019
The dapper Mr. Brown in the field
Brown with the 1908 T. rex
In the field
A formal portrait from the early 20th century
DINOLAND at the New York World's Fair (1964-1965). Barnum Brown's last project.
GEOGRAPHY: LOCATION, LOCATION, LOCATION
Before we look at some of the remarkable ancestors of Tyrannosaurus rex, let’s get a sense of what the world looked like before and during his reign.
Approximately 252 million years ago, the Earth underwent an extraordinary extinction event. “Many geologists and paleontologists contend that the Permian extinction occurred over the course of 15 million years during the latter part of the Permian Period (299 million to 252 million years ago). However, others claim that the extinction interval was much more rapid, lasting only about 200,000 years, with the bulk of the species loss occurring over a 20,000-year span near the end of the period. The Permian extinction was characterized by the elimination of over 95 percent of marine and 70 percent of terrestrial species.” (Encyclopaedia Britannica, 2019; John P. Rafferty, Editor.) The causes remain ambiguous, though these are the most often mentioned: Temperature crises as the continents began to pull apart; alteration of the carbon cycle; population explosion of methane-producing microbes; volcanic activity in what is currently Siberia; a comet or asteroid strike. Whether one or all of these instigated the great die-off, the world was left open to whole new groups of animals, including the dinosaurs.
The Paleozoic Era was over; the Mesozoic had begun, an Era divided into three distinct Periods: the Triassic, the Jurassic, and the Cretaceous.
The earliest dinosaurs emerged around 230 million years ago during the Triassic; many of them were bipedal, and several of those species would eventually evolve--around 165 million years ago (during the middle Jurassic)--into the great carnivorous bipeds that make up the Tyrannosaur family, of which Tyrannosaurus rex is but one, late-blooming member.
All well and good; but what kind of world did these animals live on?
What you have below are a series of maps. To get a larger image, just click on the picture. As you can readily see, the land masses of the planet were moving around greatly--splitting and converging just as they are today. Just as we experience earthquakes and volcanoes, so the dinosaurs would have been familiar with these catastrophic upheavals as well. And, also like today, the shifting continents would change everything from ocean currents and temperatures to atmospheric composition, which in turn would alter the evolution of plant and animal life. So when we say the earliest members of the Tyrannosaur lineage--like Kileskus, Proceratosaurus, and Guanlong--lived between 167 and 160 million years ago, we must realize that the planet was geographically and geologically quite different from the planet that T. rex roamed on 68 to 66 million years ago.
THE EARLY CRETACEOUS (approx. 140 million years ago)
NORTH AMERICA approximately 100 million years ago
THE LATE CRETACEOUS PERIOD
66 MILLION YEARS AGO--when the comet hit
MEET THE FAMILY
Below you’ll find 22 of the relatives of T. rex--a number that continues to grow because each year new members of the Tyrannosaur family are described. Further, it’s important to note that a number of these species lived concurrently, often on the same continent, and just as often separately on different land masses. So, as they used to say on television newscasts, "stay tuned"; what we think we know today about numbers and morphology may be (will be?) upturned tomorrow. As already cited, probably the greatest example of our changing understanding of this lineage was the discovery that all tyrannosaurs bore feathers at some point (or for the entirety) of their lifetimes. When the original Jurassic Park films were released in the early-to-mid-1990s--the same time the remodeled dinosaur halls opened at the American Museum of Natural History--no one knew that. A mere twenty years later, it’s all about the feathers--not to mention the strange headcrests on basal tyrannosaurs. Who knows what the next twenty years will bring?
Tyrannosauroidea (meaning ‘tyrant lizard forms’) is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period. By the end of the Cretaceous Period, tyrannosauroids were the dominant large predators in the Northern Hemisphere, culminating in the gigantic Tyrannosaurus rex itself. Fossils of tyrannosauroids have been recovered on what are now the continents of North America, Europe, Asia, South America and Australia. (Paleontology World)
Dating from the Middle Jurassic Period, Kileskus is a contender for one of the earliest tyrannosaurs. The partial skull remains have revealed the presence of a crest that rose up from the snout. Beyond this the only thing that can be said about Kileskus is that it appears to belong in a basal position of the Proceratosauridae, the group thought to belong alongside the earliest tyrannosaurs.
NOTE: The Proceratosauridae are a branch of the Tyrannosauroidea Super Family. They lived from approximately 165 Mya (Jurassic) to 120 Mya (Cretaceous). As you will read and see in the following links, there are differences of opinion regarding exactly where to place some species:
Proceratosaurus is a genus of small-sized (~3 metres (9.8 ft) long) carnivorous theropod dinosaur from the Middle Jurassic of England. It was originally thought to be an ancestor of Ceratosaurus, due to the similar small crest on its snout. Now, however, it is considered a coelurosaur, specifically one of the earliest known members of Tyrannosauroidea, the clade of basal relatives of the tyrannosaurs. The type specimen is held in the London Museum of Natural History and was recovered in 1910 at Minchinhampton while excavating for a reservoir. Minchinhampton an ancient market town on a hilltop, 4 miles (6.4 km) south south-east of Stroud, Gloucestershire, England, in the Cotswolds.
Named from the Chinese words guan, meaning 'crown', and long, meaning 'dragon,’ in reference to its flashy head-crest, Guanlong is the most elaborate of any known theropod dinosaur. The species name comes from the Chinese word wucai meaning 'five colours' and refers to the multi-hued rocks at Wucaiwan, the badlands where the fossils were found. Guanlong wucaii is one of the most primitive tyrannosaurs known. It hunted its prey 95 million years before T. rex lived. According to the Australian Museum, the name is pronounced GWON-long woo-kay-eye.
Yutyrannus (meaning "feathered tyrant") is a genus of tyrannosauroid dinosaurs which contains a single known species, Yutyrannus huali. This species lived during the early Cretaceous period in what is now northeastern China. Three fossils of Yutyrannus huali—all found in the rock beds of Liaoning Province—are currently the largest-known dinosaur specimens that preserve direct evidence of feathers (as of 2019).
Sinotyrannus (meaning "Chinese tyrant") is a genus of large basal proceratosaurid dinosaur, a relative of tyrannosaurids which flourished in North America and Asia during the Jurassic and early Cretaceous periods. Sinotyrannus is known from a single incomplete fossil specimen including a partial skull, from the Early Cretaceous Jiufotang Formation of Liaoning, China. Though it is not much younger than primitive tyrannosauroids such as Dilong, it is similar in size to later forms such as Tyrannosaurus. It was much larger than contemporary tyrannosauroids; reaching a total estimated length of 9–10 m (30–33 ft), it is the largest known theropod from the Jiufotang Formation.
Dilong (which means 'emperor dragon') is a genus of basal tyrannosauroid dinosaur. The only species is Dilong paradoxus. It is from the Lower Cretaceous Yixian Formation near Lujiatun, Beipiao, in the western Liaoning province of China. It lived about 126 million years ago. This small, earlier relative of Tyrannosaurus rex was the first tyrannosaur found with direct evidence for feathers. Dilong paradoxus is one of the smallest tyrannosaurs known, reaching only about two metres in length, and had an unusual Y-shaped skull crest (two ridges running along its snout). Unlike later tyrannosaurs, most early tyrannosaurs such as Dilong had three fingers and relatively long arms.
Dating back around one-hundred and fifty-two million years ago, Stokesosaurus is one of the earliest representatives of the tyrannosaur lineage, being only slightly later than Guanlong. At up to four meters long, Stokesosaurus resembled the juvenile forms of later tyrannosaurids, and was a fleet-footed predator relying upon speed to catch prey. Stokesosaurus possibly remained at these smaller sizes because other larger predators such as Allosaurus were dominant at the time.
Eotyrannus lengi (meaning "dawn tyrant") is a species of tyrannosauroid theropod dinosaur hailing from the Early Cretaceous Wessex Formation beds, included in Wealden Group, located in the southwest coast of the Isle of Wight, United Kingdom. The remains (MIWG1997.550), consisting of assorted skull, axial skeleton and appendicular skeleton elements, from a juvenile or subadult, found in a plant debris clay bed, were described by Hutt et al. in early 2001. The etymology of the generic name refers to the animals classification as an early tyrannosaur or "tyrant lizard", while the specific name honors the discoverer of the fossil.
Xiongguanlong ("Grand Pass dragon") is a genus of tyrannosauroid dinosaur that lived in the Early Cretaceous of what is now China. The type species is X. baimoensis (White Ghost Castle), described online in 2009 by a group of researchers from China and the United States, and formally published in January 2010. The genus name refers to the city of Jiayuguan, a city in northwestern China. The specific name is derived from bai mo, "white ghost", after the "white ghost castle", a rock formation near the fossil site. The fossils include a skull, vertebrae, a right ilium and the right femur. The rocks it was found in are from the Aptian to Albian stages of the Cretaceous, between 125 and 100 million years ago.
Dryptosaurus is a genus of tyrannosauroid that lived approximately 67 million years ago during the latter part of the Cretaceous period in what is now New Jersey. Dryptosaurus was a large, bipedal, ground-dwelling carnivore, that could grow up to 7.5 m (25 ft) long. Although largely unknown now outside of academic circles, a famous painting of the genus by Charles R. Knight made it one of the more widely known dinosaurs of its time, in spite of its poor fossil record. First described by Edward Drinker Cope in 1866 and later renamed by Othniel C. Marsh in 1877, Dryptosaurus is among the first theropod dinosaurs known to science.
THEN: Classic 1897 painting of DRYPTOSAURUS by Charles R. Knight
NOW: A more recent depiction of DRYPTOSAURUS by webartist Durbed
Range 74-72 mya/New Mexico (USA)
Bistahieversor (meaning "Bistahi destroyer") is a genus of tyrannosaurid dinosaur. Bistahieversor existed in the Late Cretaceous Hunter Wash member of the Kirtland Formation (New Mexico), which has been dated to 74.55 ± 0.29 Mya. The name Bistahieversor comes from the Navajo Bistahí, or "place of the adobe formations" in reference to the Bisti/De-Na-Zin Wilderness where it was found, and eversor, meaning "destroyer." The skull of Bistahieversor has many features that are considered primitive for the Tyrannosaurid group, but most importantly, a noticeable depth that is lacking in other, and later, tyrannosaurid species. This is significant because it was once thought that only the later and more advanced tyrannosaurids, like Tyrannosaurus itself, had deeper snouts. Bistahieversor was also joined by the tyrannosaurid Teratophoneus (see further description of this dinosaur below on this page), another of its kind that seems to have been restricted to the Southern US even though it also lived during the Campanian. Both Bistahieversor and Teratophoneus display more basal tyrannosaurid morphology, and both are known only from the southern area of what was once called Laramidia. This was the western half of North America that was separated from the eastern half by the Western Interior Seaway. Rising sea levels combined with mountain ranges being pushed up could have isolated the southern tyrannosaurids from the North, causing the retention of the more basal features seen in Bistahieversor, so late in the geological timescale.
Appalachiosaurus (Appalachian lizard") is a genus of tyrannosauroid theropod dinosaur from the Late Cretaceous Period of eastern North America. Like almost all theropods, it was a bipedal predator. Only a juvenile skeleton has been found, representing an animal over 7 meters (23 ft) long and weighing over 600 kilograms (1300 lb), which indicates an adult would have been even larger. It is the most completely known theropod from the eastern part of North America. Fossils of Appalachiosaurus were found in central Alabama, from the Demopolis Chalk Formation. This formation dates to the middle of the Campanian stage of the Late Cretaceous, or around 77 million years ago. Fossil material assigned to A. montegomeriensis is also known from the Donoho Creek and Tar Heel-Coachman formations of North and South Carolina.
Albertosaurus ("Alberta lizard") is a genus of tyrannosaurid theropod dinosaurs that lived in western North America during the Late Cretaceous Period, about 70 million years ago. The type species, A. sarcophagus, lived in Western Canada but, according to the San Diego Museum of Natural History, fragmentary fossil remains have been found as far south as Baja California. Scientists disagree on the content of the genus, with some recognizing Gorgosaurus libratus (see below on this page) as a second species. As a tyrannosaurid, Albertosaurus was a bipedal predator with tiny, two-fingered hands and a massive head that had dozens of large, sharp teeth. It may have been at the top of the food chain in its local ecosystem. While Albertosaurus was large for a theropod, it was much smaller than its larger and more famous relative Tyrannosaurus rex, growing nine to ten meters long and possibly weighing less than 2 metric tons.
ALBERTOSAURUS model at the San Diego Museum of Natural History (non-feathered)
A feathered ALBERTOSAURUS as seen in the documentary "The March of the Dinosaurs" (c) 2011
Range 80-73 mya/Alberta (Canada)
Gorgosaurus ("dreadful lizard") is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, between about 76.6 and 75.1 million years ago. Fossil remains have been found in the Canadian province of Alberta and possibly the U.S. state of Montana. Paleontologists recognize only the type species, G. libratus, although other species have been erroneously referred to the genus. Like most known tyrannosaurids, Gorgosaurus was a bipedal predator weighing more than two metric tons as an adult; dozens of large, sharp teeth lined its jaws, while its two-fingered forelimbs were comparatively small. Gorgosaurus was most closely related to Albertosaurus, and more distantly related to the larger Tyrannosaurus. Gorgosaurus and Albertosaurus are extremely similar, distinguished mainly by subtle differences in the teeth and skull bones. Some experts consider G. libratus to be a species of Albertosaurus; this would make Gorgosaurus a junior synonym of that genus. Gorgosaurus lived in a lush floodplain environment along the edge of an inland sea. It was an apex predator, preying upon abundant ceratopsids and hadrosaurs.
Qianzhousaurus is a genus of tyrannosaurid dinosaur. There is currently only one species named, the type species Qianzhousaurus sinensis. It is nicknamed "Pinocchio rex" for its long snout in comparison with other known tyrannosaurs. It was discovered in southern China and first published in the journal Nature Communications in May 2014. Aside from its signature snout, it also had long, narrow teeth, while in comparison, relatives like Tyrannosaurus had thick teeth and powerful, deep-set jaws. The bones of Qianzhousaurus were discovered by workmen at a construction site near the city of Ganzhou, who then took them to a local museum.
Alioramus has stirred a lot of interest and controversy since its discovery, and even though Alioramus has earned worldwide popularity, it was for a long time only known from a partial skull and three metatarsals (foot bones). Another problem was the fact that when reconstructed, the skull was narrow and low like in some juvenile forms of other better known tyrannosauroids. This led to Alioramus being considered for a long time to be a juvenile of the larger Tarbosaurus by many paleontologists until the discovery of the second species A.altai in 2009. This specimen is thought to represent a sub-adult because the skull bones had begun fusing together, indicating that the individual was approaching maximum size but still not even close to Tarbosaurus. Further support for keeping Alioramus its own separate genus comes from the fact that Alioramus had many more teeth in its mouth than Tarbosaurus individuals that were both juvenile and fully grown. Also Alioramus has a series of five crests on the top of its snout which so far remain unknown in Tarbosaurus.
With a name that translates to English as ‘Monstrous murderer’, Teratophoneus has arguably one of the most apt names of any dinosaur, although the remains suggest that it was smaller than many of the other tyrannosaurids. The species name, T.curriei (2011), is in honor of paleontologist Philip J. Currie. Teratophoneus was a very interesting find when it was discovered in Utah. Whereas other tyrannosaurids of the day such as Daspletosaurus were active in the North, Teratophoneus was active in the South. Together with another tyrannosaurid, Bistahieversor, this has pushed the known range of the tyrannosaurids in North America even further south.
Nanuqsaurus (meaning "polar bear lizard") is an extinct genus of carnivorous tyrannosaurid theropod known from the Late Cretaceous (early Late Maastrichtian stage) Prince Creek Formation of the North Slope of Alaska (2014). It contains a single species, Nanuqsaurus hoglundi, known only from a partial skull.
Nanotyrannus ("dwarf tyrant"), first described in 1946, is a potentially dubious genus of tyrannosaurid dinosaur. It is known only from two specimens (possibly three), which may be juvenile specimens of the contemporary species Tyrannosaurus 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 (Rockford, Illinois) 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. On the other hand, some, such as Peter Larson, continued to support the hypothesis that Nanotyrannus lancensis was a separate but closely related species. In 2015, Professor Phil Manning and Dr. Charlotte Brassie of Manchester University studied Jane using a LIDAR scanner, and using data and computer modelling, their reconstruction of body mass suggested that Jane had a 600 kg - 900 kg body mass, far lower than would be expected for a Tyrannosaurus. Also in 2015, Assistant Professor Holly Woodward Ballard of Oklahoma State University used histology to examine a thin slice of Jane's femur. Counting the rings within Jane's bone material showed that Jane was 11 years old, and bone histology suggests that Jane was immature and still growing. The actual scientific study of "Jane" may determine whether Nanotyrannus lancensis is a valid species or if it represents a juvenile T. rex.
Zhuchengtyrannus (meaning "Zhucheng tyrant") is a genus of tyrannosaurid theropod dinosaur known from the Late Cretaceous period of Shandong Province, China. It belongs to the tyrannosaurinae subfamily, and contains a single species, Zhuchengtyrannus magnus, first described in 2011.
Daspletosaurus was a genus of tyrannosaurid dinosaur that lived in western North America between about 77 and 74 million years ago, during the Late Cretaceous Period. The genus Daspletosaurus contains two species. Fossils of the earlier type species, D. torosus, have been found in Alberta, while fossils of the later second species, D. horneri, have been found only in Montana. A possible third species, also from Alberta, awaits formal identification. Daspletosaurus is closely related to the much larger and more recent tyrannosaurid Tyrannosaurus rex. Like most tyrannosaurids, Daspletosaurus was a multi-ton bipedal predator equipped with dozens of large, sharp teeth. Daspletosaurus had the small forelimbs typical of tyrannosaurids, although they were proportionately longer than in other genera. As an apex predator, Daspletosaurus was at the top of the food chain, probably preying on large dinosaurs like the ceratopsid Centrosaurus and the hadrosaur Hypacrosaurus. In some areas, Daspletosaurus coexisted with another tyrannosaurid, Gorgosaurus, though there is some evidence of niche differentiation between the two.
Tarbosaurus (meaning "alarming lizard") is a genus of tyrannosaurid theropod dinosaur that flourished in Asia about 70 million years ago, at the end of the Late Cretaceous Period. Fossils have been recovered in Mongolia, with more fragmentary remains found further afield in parts of China. Although many species have been named, modern paleontologists recognize only one, T. bataar, as valid (discovered in 1946). Some experts see this species as an Asian representative of the North American genus Tyrannosaurus; this would make the genus Tarbosaurus redundant. Tarbosaurus and Tyrannosaurus, if not synonymous, are at least closely related genera. Alioramus, also from Mongolia, has previously been thought by some authorities to be the closest relative of Tarbosaurus, though this has since been disproven with the discovery of Qianzhousaurus and the description of the Alioramini. Like most known tyrannosaurids, Tarbosaurus was a large bipedal predator, weighing up to five tons and equipped with about sixty large teeth. It had a unique locking mechanism in its lower jaw and the smallest forelimbs relative to body size of all tyrannosaurids, renowned for their disproportionately tiny, two-fingered forelimbs. Tarbosaurus lived in a humid floodplain crisscrossed by river channels. In this environment, it was an apex predator, probably preying on other large dinosaurs like the hadrosaur Saurolophus or the sauropod Nemegtosaurus. Tarbosaurus is represented by dozens of fossil specimens, including several complete skulls and skeletons. These remains have allowed scientific studies focusing on its phylogeny, skull mechanics, and brain structure.
Tyrannosaurus is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex (rex meaning "king" in Latin), often called T. rex, is one of the most well-represented of the large theropods. Tyrannosaurus lived throughout what is now western North America, on what was then an island continent known as Laramidia. Tyrannosaurus had a much wider range than other tyrannosaurids. Fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper Cretaceous Period, 68 to 66 million years ago. It was the last known member of the tyrannosaurids, and among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction event. Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to its large and powerful hindlimbs, Tyrannosaurus forelimbs were short but unusually powerful for their size and had two clawed digits. The most complete specimen measures up to 12.3 m (40 ft) in length though T. rex could grow to lengths of over 12.3 m (40 ft), up to 3.66 meters (12 ft) tall at the hips, and according to most modern estimates 8.4 metric tons (9.3 short tons) to 14 metric tons (15.4 short tons) in weight. Although other theropods rivaled or exceeded Tyrannosaurus rex in size, it is still among the largest known land predators and is estimated to have exerted the strongest bite force among all terrestrial animals. By far the largest carnivore in its environment, Tyrannosaurus rex was most likely an apex predator, preying upon hadrosaurs, armored herbivores like ceratopsians and ankylosaurs, and possibly sauropods. Some experts have suggested the dinosaur was primarily a scavenger. The question of whether Tyrannosaurus was an apex predator or a pure scavenger was among the longest debates in paleontology. Most paleontologists today accept that Tyrannosaurus was both an active predator and a scavenger. More than 50 specimens of Tyrannosaurus rex have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including its life history and biomechanics. The feeding habits, physiology and potential speed of Tyrannosaurus rex are a few subjects of debate. Its taxonomy is also controversial, as some scientists consider Tarbosaurus bataar from Asia to be a second Tyrannosaurus species while others maintain Tarbosaurus is a separate genus. Several other genera of North American tyrannosaurids have also been synonymized with Tyrannosaurus.
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