Changes

T-rex was a large [[theropod]], with recovered specimens averaging between 36-40 feet in length and standing about 12 feet at the hips <ref>Brochu, C.R. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. Memoirs of the Society of Vertebrate Paleontology. 7: 1-138.</ref>.  The weight of an adult has been estimated to be between 5-7 tons, roughly comparable to a living African [[elephant]].

T-rex was a large [[theropod]], with recovered specimens averaging between 36-40 feet in length and standing about 12 feet at the hips <ref>Brochu, C.R. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. Memoirs of the Society of Vertebrate Paleontology. 7: 1-138.</ref>.  The weight of an adult has been estimated to be between 5-7 tons, roughly comparable to a living African [[elephant]].

The skull was massively-built and robust.  The sixty teeth which lined the mouth were up to 7-inches long and banana-shaped, with cutting serrations on each edge.  T-rex also had forward-facing eyes, giving it [[Binocular vision|binocular vision]].  The other noticeable feature was the small forearms bearing only two clawed fingers, which many scientists have declared useless or vestigial.  But the shoulder blades were relatively-large, indicating the arms were still well-muscled, and it has been postulated that these arms aided T-rex in lifting itself up on its hind feet from a prone position. [http://www.sciam.com/article.cfm?id=if-t-rex-fell-how-did-it]

The skull was massively-built and robust.  The sixty teeth which lined the mouth were up to 7-inches long and banana-shaped, with cutting serrations on each edge.  T-rex also had forward-facing eyes, giving it [[Binocular vision|binocular vision]].  The other noticeable feature was the small forearms bearing only two clawed fingers, which many scientists have declared useless or vestigial.  But the shoulder blades were relatively-large, indicating the arms were still well-muscled, and it has been postulated that these arms aided T-rex in lifting itself up on its hind feet from a prone position.<ref>http://www.sciam.com/article.cfm?id=if-t-rex-fell-how-did-it</ref>

====Diet====

====Diet====

Some scientists, notably Dr. Jack Horner [http://news.bbc.co.uk/2/hi/science/nature/3112527.stm][http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2001/02/05/MN133208.DTL&type=science] of the Museum of the Rockies in Bozeman, Montana, have put forward the hypothesis that T-rex was exclusively a scavenger. They cite as their evidence the relatively-slow estimated speed of the animal - no more than 15 miles per hour - as well as the small forelimbs and the large olfactory casts made inside their skulls, which indicated a powerful sense of smell.  This may be partially true, since most carnivores today will happily scavenge available meat. However, it probably was not an ''exclusive'' scavenger, as most meat-eaters must also hunt in order to survive. T-rex's jaws were also quite adaptive to grabbing live prey. In opposition to the scavenger theory there are several specimens of dinosaur - principally ''Edmontosaurus'' and ''Triceratops'' - in North American museums which show clear bite wounds that have healed over, and T-rex teeth easily fit inside them. [http://animals.howstuffworks.com/dinosaurs/t-rex-predator-or-scavenger.htm/printable][http://www.unearthingtrex.com/pages/rex_behaviour.html]

Some scientists, notably Dr. Jack Horner<ref>http://news.bbc.co.uk/2/hi/science/nature/3112527.stm</ref><ref>http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2001/02/05/MN133208.DTL&type=science</ref> of the Museum of the Rockies in Bozeman, Montana, have put forward the hypothesis that T-rex was exclusively a scavenger. They cite as their evidence the relatively-slow estimated speed of the animal - no more than 15 miles per hour - as well as the small forelimbs and the large olfactory casts made inside their skulls, which indicated a powerful sense of smell.  This may be partially true, since most carnivores today will happily scavenge available meat. However, it probably was not an ''exclusive'' scavenger, as most meat-eaters must also hunt in order to survive. T-rex's jaws were also quite adaptive to grabbing live prey. In opposition to the scavenger theory there are several specimens of dinosaur - principally ''Edmontosaurus'' and ''Triceratops'' - in North American museums which show clear bite wounds that have healed over, and T-rex teeth easily fit inside them.<ref>http://animals.howstuffworks.com/dinosaurs/t-rex-predator-or-scavenger.htm/printable</ref><ref>http://www.unearthingtrex.com/pages/rex_behaviour.html</ref>

====Bite strength====

====Bite strength====

Recent estimates based on computer models, scale models of skulls, and comparisons with living animals suggest T-rex had one of the strongest bites of any animal.  Experiments conducted by Dr. Gregory Erickson when he was a graduate student at the University of California (Berkeley) determined that a minimum of 1,440 pounds of pressure from its front teeth alone could put a 11.5 mm-deep hole in bone, while 3,011 pounds of pressure came from its back teeth [http://news-service.stanford.edu/pr/96/960827tyrexbite.html][http://science.discovery.com/videos/mammals-vs-dinos-t-rex-bite-force.html][http://news.nationalgeographic.com/news/2006/04/0405_060405_trex_video.html][http://videos.howstuffworks.com/discovery/28239-assignment-discovery-tyrannosaurus-rexs-bite-force-video.htm].  The strength of the bite may have been as much as four tons or more, according to Dr. Eric Snively of the University of Alberta, who discovered the significance of fused nasal bones unique to T-rex.  "Fused, arch-like nasal bones are a unique feature of tyrannosaurids," he said. "This adaptation, for instance, was keeping the T. rexes from breaking their own skull while breaking the bones of their prey."  A fused nasal bone channels the force of the bite from the skull to the prey item; this, with the combination of extremely-powerful neck muscles, convinced Dr. Snively and his colleagues that an adult T-rex could potentially use 200,000 newtons of force when pulling meat off a carcass. [http://www.livescience.com/animals/070518_dino_nose.html]

Recent estimates based on computer models, scale models of skulls, and comparisons with living animals suggest T-rex had one of the strongest bites of any animal.  Experiments conducted by Dr. Gregory Erickson when he was a graduate student at the University of California (Berkeley) determined that a minimum of 1,440 pounds of pressure from its front teeth alone could put a 11.5 mm-deep hole in bone, while 3,011 pounds of pressure came from its back teeth<ref>http://news-service.stanford.edu/pr/96/960827tyrexbite.html</ref><ref>http://science.discovery.com/videos/mammals-vs-dinos-t-rex-bite-force.html</ref><ref>http://news.nationalgeographic.com/news/2006/04/0405_060405_trex_video.html</ref><ref>http://videos.howstuffworks.com/discovery/28239-assignment-discovery-tyrannosaurus-rexs-bite-force-video.htm</ref>.  The strength of the bite may have been as much as four tons or more, according to Dr. Eric Snively of the University of Alberta, who discovered the significance of fused nasal bones unique to T-rex.  "Fused, arch-like nasal bones are a unique feature of tyrannosaurids," he said. "This adaptation, for instance, was keeping the T. rexes from breaking their own skull while breaking the bones of their prey."  A fused nasal bone channels the force of the bite from the skull to the prey item; this, with the combination of extremely-powerful neck muscles, convinced Dr. Snively and his colleagues that an adult T-rex could potentially use 200,000 newtons of force when pulling meat off a carcass. <ref>http://www.livescience.com/animals/070518_dino_nose.html</ref>

In 1995 a coprolite (fossilized dung) was discovered near Eastend, Saskatchewan, and determined to have been from a T-rex based on the size as well as the bone fragments within from a ''Triceatops'', leading scientists to speculate that the power of a T-rex bite could shatter bone. [http://www.lubbockonline.com/stories/061898/LA0709.001.shtml]

In 1995 a coprolite (fossilized dung) was discovered near Eastend, Saskatchewan, and determined to have been from a T-rex based on the size as well as the bone fragments within from a ''Triceatops'', leading scientists to speculate that the power of a T-rex bite could shatter bone.<ref>http://www.lubbockonline.com/stories/061898/LA0709.001.shtml</ref>

== Fossils ==

== Fossils ==

[[Young Earth Creationism|Young Earth Creationists]] believe that they became extinct sometime since the [[Great Flood]], dated to approximately 4,500 years ago.  

[[Young Earth Creationism|Young Earth Creationists]] believe that they became extinct sometime since the [[Great Flood]], dated to approximately 4,500 years ago.  

[[Theory of evolution|Evolutionary]] scientists believe that the T-rex lived at the end of the [[Cretaceous]] period, dated to approximately 65 million years ago, and that modern birds are the descendants of dinosaurs such as T-rex. <ref>[http://www.cnn.com/2007/TECH/science/04/12/dinosaur.reut/index.html Bird Family Ties]</ref><ref>[http://www.livescience.com/animalworld/ap_trex_tissues.html T Rex Tissue]</ref>

[[Theory of evolution|Evolutionary]] scientists believe that the T-rex lived at the end of the [[Cretaceous]] period, dated to approximately 65 million years ago, and that modern birds are the descendants of dinosaurs such as T-rex. <ref>[http://www.cnn.com/2007/TECH/science/04/12/dinosaur.reut/index.html Bird Family Ties]</ref><ref>http://www.livescience.com/animalworld/ap_trex_tissues.html T Rex Tissue</ref>

==References==

==References==