Tyrannosaurus

Tyrannosaurus was a genus of large coelurosaurian theropod dinosaur. Native to the western United States and western Canada, the type and only species, T. rex, is likely the most famous of all dinosaurs. It was also one of the last, appearing only 68.5 MYA, approximately 3 million years before the Cretaceous-Tertiary extinction event. Although often depicted as the largest theropod, this is no longer the case, as the allosauroids Carcharodontosaurus and Giganotosaurus, according to recent estimates, are of comparable size, and the African spinosauroid Spinosaurus is significantly larger still.

More than 30 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 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, with some scientists considering Tarbosaurus bataar from Asia to represent a second species of Tyrannosaurus and others maintaining Tarbosaurus as a separate genus. Several other genera of North American tyrannosaurids have also been synonymized with Tyrannosaurus.

Discovery and fossil record
Henry Fairfield Osborn, president of the American Museum of Natural History, named Tyrannosaurus rex in 1905. The generic name is derived from the Greek words τυράννος (tyrannos, meaning "tyrant") and σαύρος (sauros, meaning "reptile"). Osborn used the Latin word rex, meaning "king", for the specific name. The full binomial therefore translates to "king tyrant reptile", emphasizing the animal's size and perceived dominance over other species of the time.

Teeth from what is now documented as a Tyrannosaurus rex were found in 1874 by A. Lakes near Golden, Colorado. In the early 1890s, J. B. Hatcher collected postcranial elements in eastern Wyoming. The fossils were believed to be from a large species of Ornithomimus (O. grandis) but are now considered Tyrannosaurus rex. Vertebral fragments found by E. D. Cope in western South Dakota in 1892 and named as Manospondylus gigas have also been recognized as belonging to Tyrannosaurus rex.

Barnum Brown, assistant curator of the American Museum of Natural History, found the first partial skeleton of Tyrannosaurus rex in eastern Wyoming in 1900. H. F. Osborn originally named this skeleton Dynamosaurus imperiosus in a paper in 1905. Brown found another partial skeleton in the Hell Creek Formation in Montana in 1902. Osborn used this holotype to describe Tyrannosaurus rex in the same paper in which D. imperiosus was described. In 1906, Osborn recognized the two as synonyms, and acted as first revisor by selecting Tyrannosaurus as the valid name. The original Dynamosaurus material resides in the collections of the Natural History Museum, London.

In total, Brown found five Tyrannosaurus partial skeletons. In 1941, Brown's 1902 find was sold to the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. Brown's fourth and largest find, also from Hell Creek, is on display in the American Museum of Natural History in New York.

AMNH 5027
AMNH 5027 was discovered by Barnum Brown in 1907. It was found in southern Montana and is approximately 3.25 metres tall and over 12 metres long. Its skull was complete and was the first complete skull of any Tyrannosaurus.

BHI 3033
BHI 3033, commonly known as "Stan", was discovered in South Dakota in the mid-1900s. It was a member of the gracile form, thought to be male. It is one of the smaller specimens, being noticeably smaller than the famous AMNH 5027. It stands slightly over 3 metres tall, and is 10.5 metres long. Though often thought as a mature male, it may in fact have been a sub-adult.

FMNH PR2081
FMNH PR2081, commonly known as "Sue", is the largest and most complete Tyrannosaurus specimen as of yet. While potentially larger specimens such as MOR 008 exist, no accurate size estimates have been made yet, so "Sue" retains its title as the largest Tyrannosaurus for the moment. It stands almost 3.6 metres tall and is approximately 12.3 metres long.

BMRP 2002.4.1
BMRP 2002.4.1, commonly known as "Jane", was a small tyrannosaurid initially described as "Nanotyrannus lancensis", but more likely to be a juvenile Tyrannosaurus. 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. This research is currently being undertaken by Robert T. Bakker, Peter Larson, and Phil Currie, and should help settle the question once it is officially published.

Description and Paleobiology
Tyrannosaurus was a very large theropod; in fact for many years it was referred to as the largest theropod, despite the fact that the forgotten Spinosaurus holotype was over two metres longer than the largest Tyrannosaurus specimen at the time. Currently there are at least three, possibly four theropods that are known to be larger than Tyrannosaurus, and yet it was still impressive.

An average-sized Tyrannosaurus may be 11.8 metres long, 3.4 metres tall, and five tonnes in weight. Many specimens are larger, however, and the largest known yet, "Sue", is approximately 12.3 metres long, pressing 3.6 metres in height, and more than 7 tonnes. A larger skull, known as MOR 008, is known and may have come from an animal 13.2 metres in length. In addition, Jack Horner claims to have discovered a 14-metre specimen nicknamed "Celeste". However, Horner has not published any official size estimates and no one has seen the specimen but Horner, so it seems probable that "Celeste" is not genuine.

In terms of body shape, Tyrannosaurus was a typical theropod. The hind legs were fairly long in proportion to body size and ended in three-toed feet. The front legs, however, were severely reduced, being only as long as a human arm and possessing two fingers. The function of the front legs has generally been a mystery. At the rear of the body is a long, tapering tail. The body itself is broad and deep, and the skull is large in proportion to body size. The bones are very thick and powerful, and the jaw muscles would have been powerful enough to give the animal one of the strongest bite forces of extinct animals. The teeth were D-shaped in cross-section, serrated, and resilient; they would have been more difficult to break than those of other theropods and thus better adapted for making a lethal bite.

Tyrannosaurus, like most tyrannosauroids, had a fairly large brain compared to other large dinosaurs. This suggests that the traditional depiction of it being an extremely stupid animal may be incorrect. Scans have determined that 65% of that made its olfactory bulb. This indicates that it had an acute sense of smell, possibly being able to pick up scents from miles away.

The bite force of Tyrannosaurus has been a matter of debate. The most recent studies on Tyrannosaurus bite force have put the bite force of this animal at 20-23.5t. If these are correct, Tyrannosaurus would have possesed the most powerful bite of all time. However, a slightly older study that measured how much force was needed to make the wounds seen in a Triceratops bone got the feeding bite force for Tyrannosaurus at 3t. Its maximum bite would un-doubtably be higher. However, not many if any animal at all to today has a maximum bite over 7 times the strength of its feeding bite which has lead to some criticism of that study.

Tyrannosaurus rex arms are very small relative to overall body size, measuring only 1 metre (3.3 ft) long. However, they are not vestigial but instead show large areas for muscle attachment, indicating considerable strength. This was recognized as early as 1906 by Osborn, who speculated that the forelimbs may have been used to grasp a mate during copulation. It has also been suggested that the forelimbs were used to assist the animal in rising from a prone position. Another possibility is that the forelimbs held struggling prey while it was killed by the tyrannosaur's enormous jaws. This hypothesis may be supported by biomechanical analysis.

The forelimbs might have been used to help T. rex rise from a resting pose, as seen hereTyrannosaurus rex forelimb bones exhibit extremely thick cortical bone, indicating that they were developed to withstand heavy loads. The biceps brachii muscle of a full-grown Tyrannosaurus rex was capable of lifting 199 kilograms (439 lb) by itself; other muscles such as the brachialis would work along with the biceps to make elbow flexion even more powerful. The M. biceps muscle of T. rex was 3.5 times as powerful as the human equivalent. A Tyrannosaurus rex forearm also had a reduced range of motion, with the shoulder and elbow joints allowing only 40 and 45 degrees of motion, respectively. The heavy build of the arm bones, extreme strength of the muscles, and limited range of motion may indicate a system evolved to hold fast despite the stresses of a struggling prey animal. Carpenter and Smith dismissed notions that the forelimbs were useless or that Tyrannosaurus rex was an obligate scavenger.

Tyrannosaurus's skull was significantly different from those of large non-tyrannosauroid theropods. It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision<. The eye-sockets of tyrannosaurs are positioned so that the eyes would point forward, giving them binocular vision slightly better than that of modern hawks.

Behaviour
It has been suggested by some paleontologists, notably Jack Horner, that Tyrannosaurus was primarily, or even exclusively, a scavenger. The evidence for their arguement includes the fact that Tyrannosaurus had powerful, bone-crushing jaws, and an acute sense of smell, both of which are characteristics of scavengers. There has been heavy criticism of this belief; it has been argued that a scavenger would not need such powerful jaws or such effective binocular vision. The most likely conclusion is that Tyrannosaurus was an opportunist, being primarily a hunter, but also taking carrion when it got the chance, just like most other carnivores.

Fossil remains of two if its close relatives, Tarbosaurus and Albertosaurus, have been found in large gatherings or "bonebeds", indicating that they may have demonstrated social behaviour, as perhaps did Tyrannosaurus itself. This belief has been criticized, however, as it is thought that the heavyweight adults would not be able to move quickly enough to chase down prey, and that the juveniles were not powerful enough to kill large dinosaurs. Those in favour of social behaviour in large theropods, such as Phil Currie, have suggested that sub-adults would run ahead of the adults, weakening the prey so that it would be unable to escape, allowing the adults to catch up and kill the prey. Whether it was solitary or communal, Tyrannosaurus would have been a fearsome predator. Despite its fearsome weaponry, dinosaurs such as Ankylosaurus may have proven to be too formidably defended for Tyrannosaurus to hunt.

In popular culture
Tyrannosaurus is one of the most popularized of dinosaurs. It has been in tremendous movies, shows, books, and documentaries.

Probably the most well known T.rex appears in the Jurassic Park trilogy. In these movies, especially the first and second, T.rex plays a signaficant role. The first movie of Jurassic Park, Tyrannosaurus had broke free from its theme park enclosure, and starts wandering the area, killing off some characters. The sequel to this move, The Lost World, T.rex returned as the main antagonist. However, Jurassic Park 3 only shows T.rex in a brief battle with a Spinosaurus, where it dies and is not shown for the rest of the story.

Some other movie apperances include:  T-Rex: Back to the Cretaceous (1998),  Meet the Robinsons (2007),  Night at the Museum (2006),  ''[http://en.wikipedia.org/wiki/Dinosaurus! Dinosaurus!] (1960),  The Land Before Time (1988),  The Last Dinosaur (1977), and  Ice Age: Dawn of the Dinosaurs'' (2009).

<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">T.rex has also made huge appearances is most dinosaur documentaries these past few years. The ever growing list of documentries include: ''[http://en.wikipedia.org/wiki/Dinosaur! Dinosaur!]<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Dinosaur Planet<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Prehistoric Park<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, T. Rex: New Science, New Beast<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Dino-Riders<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Dink, the Little Dinosaur<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, The Truth About Killer Dinosaurs<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Walking with Dinosaurs<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, When Dinosaurs Roamed America<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Sea Monsters - A Walking with Dinosaurs Trilogy<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Valley of the T-Rex<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Dinosaurs Decoded<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Bizarre Dinosaurs<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Animal Armageddon<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Jurassic Fight Club<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Dinolab<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, T-rex: Warrior or Wimp?<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, T. Rex: A Dinosaur in Hollywood<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, Dinosaur Revolution<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">, and Planet Dinosaur''<span style="color:rgb(0,0,0);font-family:sans-serif;line-height:19px;">.