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Tyrannosaurus rex  (Henry Osborn, 1912).

Name Means: "Tyrant Lizard" Length: 40 feet (13 m)
Pronounced: tie-Ran-o-Saw-rus Weight: 6 tons (6,000 kilos)
When it lived: Late Cretaceous - 67 MYA    
Where found: North America    

Introduction

   Tyrannosaurus rex ("king of the tyrannical lizards"), also known colloquially as "The King of the Dinosaurs," was a giant carnivorous theropod dinosaur from the Upper Maastrichtian, the last stage of the Cretaceous period, 65 to 66 million years ago.  The first discovered specimens played an important role in the Bone Wars.
   Tyrannosaurus Rex is widely regarded as the most famous dinosaur.  This is partly because it was the first very large carnivorous dinosaur to be discovered and it was long believed to have been the largest that ever lived.  Another factor was that it was probably the fiercest meat eater that ever lived. At more than 40 feet tall, it was huge and had the most powerful head of any dinosaur. It also had the biggest teeth of any dinosaur - teeth that were not only sharp and cutting edged, but also thick and strong, capable of crushing bones. While there have been sensationalistic claims of new, larger therapods "dethroning" T. rex as the King of the Dinosaurs, evidence remains scant and open to debate. T. rex will very likely remain a point of ongoing scientific research and popular culture.

Description

    After many millions of years of evolution, T. rex was an almost perfect killing machine. It was capable of running at great speed to catch whatever it wanted to eat.  It had large feet to help it run quickly through the swampy environment in which it lived, maybe as fast as 35 mph. Although it had very short arms, they were very strong. But it didn't need its arms to be an effective and efficient killer. It had enormous strength in its jaws; it could bite right through the frill of a Triceratops or into the back of a hadrosaur. In fact, the only thing that a T. rex had to fear was another T. rex. Most of the scars and wounds found on fossil bones of these great creatures seem to come from others of its kind.

Discovery

   The first specimen (a partial vertebra) was found by Edward Cope in 1892 and was described as Manospondylus gigas.  Barnum Brown, assistant curator of the American Museum of Natural History, found the second T. rex skeleton in Wyoming in 1900. Brown collected his second T. rex in 1902 and 1905 in Montana. Barnum Brown eventually found five T. rex partial skeletons. The dinosaur was assigned the name Tyrannosaurus rex in 1912 by Henry Osborn.
   T. rex is an excellent example of how our thinking about dinosaurs has changed based on how much we have learned. Back in 1915 when the first skeleton was mounted, most people thought it was a slow beast that dragged its tail along the ground. This view was partially because it would have been very expensive to mount it any other way, and scientists weren't sure how it looked in life. Now, scientists are confident that they understand how T. rex and other dinosaurs looked and lived. T. rex probably walked and ran with its back and tail parallel to the ground, its massive legs and hips a fulcrum for its body. It was an active beast, and recent evidence strongly suggests it was warm blooded.

Fossils

    T. rex is very well known. As of 2005 30 specimens had been found.  Less than half of them had significant amounts of fossil.  Only three have complete skulls. But still there is enough material to provide a very good picture of these creatures.
   the most complete Tyrannosaur rex fossil skeleton was discovered in the Hell Creek Formation near Faith, South Dakota, on August 12, 1990 .  It is 90% complete.  It was eventually named "Sue," for Susan Hendrickson, the amateur paleontologist who discovered it.  This fossil skeleton became the subject of a legal battle over its ownership. In 1997, it was settled in favor of Maurice Williams, the original land owner.  The fossil collection was sold at auction for $7.6 million by museum sponsors who gave it to the Field Museum of Natural History in Chicago.  . It has now been reassembled and is currently on exhibit. Based on Sue's fossilized bones, she died at age 28 years, having reached her full size at age 19 years. Researchers report that a sub-adult and a juvenile skeleton were found in the same quarry as Sue; this lends evidence to the possibility that T. rex ran in packs or other groups.
Another T. rex, nicknamed "Stan," in honor of amateur paleontologist Stan Sacrison, was found in the Hell Creek Formation near Buffalo, South Dakota, in the spring of 1987. After 30,000 hours of digging and preparing, a 65% complete skeleton emerged. Stan currently is on display in the Black Hills Museum of Natural History Exhibit in Hill City, South Dakota, after an extensive world tour. This tyrannosaur too was found to have many bone pathologies, including broken and healed ribs, a broken (and healed) neck and a spectacular hole in the back of its head, about the size of a T. rex tooth. Both Stan and Sue were examined by Peter Larson.

Species

    Three dinosaurs have been at various times been labeled as tyrannosaurs.  T. rex, the species type, was the first.   T. bataar is now recognized as being in a separate genus, Tarbosaurus, and as has T. torosus which is now classified as Daspletosaurus. Nonetheless, Daspletosaurus, Tarbosaurus and Tyrannosaurus are very closely related, and belong to the tribe Tyrannosaurini.
 

 

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