Tyrannosaurus Rex

Toying with a time machine, a careless traveler suddenly finds himself in a primeval forest, surrounded by spreading ferns, squat cycads, and cypresses festooned with thick curtains of moss. A swirling cloud of mosquitoes hovers above a stagnant pool, which sprouts clusters of towering reeds. Concealed just below the surface is one of nature's timeless predators, the stealthy, silent crocodile.

Suddenly, behind the bewildered wayfarer comes a snapping of branches as the trees part to reveal something even more fearsome than the submerged swamp stalker. A behemoth emerges, as tall as a two-story house and as long as a bus, its huge tail swishing back and forth ominously. The beast leans forward on stout, powerful legs, tail and body parallel to the ground, balancing on a pair of birdlike feet. Its three-foot forearms, sporting two claws, seem incongruous on this 10,000-pound frame. The gleaming, voracious eyes look straight ahead as the immense, bone-crushing jaws part to reveal a set of 50 to 60 sharp teeth, each six to eight inches in length. Frantically, the time traveler spins around and makes a mad dash for the 21st century.

No other dinosaur has achieved the renown of the fearsome Tyrannosaurus Rex- Greek for "tyrant lizard king." Extinct for 65 million years, T. Rex has nonetheless been immortalized, in film, fiction and popular imagination. Arguably the largest land carnivore ever, T. Rex roamed a semi-tropical landscape of what is now Asia and western North America during the late Cretaceous Period. Contemporaries included the horned herbivore Triceratops, the armored, club-tailed ankylosaurus, and fellow predator velociraptor, who was in reality about one-third the size depicted in the Jurassic Park movies.

The first T. Rex fossils were discovered in Montana in 1900. In 1990, a nearly complete set of bones was unearthed on an Indian reservation in South Dakota. The assembled T. Rex skeleton -nicknamed "Sue" after its discoverer- are on display at the Field Museum in Chicago, Illinois. Other archaeological finds include fossilized T. Rex skin showing that this dinosaur had a rough, scaly hide like an alligator's, and fossilized dung, revealing pieces of Triceratops bones (EnchantedLearning).

As theories about dinosaurs have evolved, so too have theories about the tyrant lizard king. Originally scientists thought that T. Rex carried itself upright, but now believe that the animal adopted a more lateral stance. In addition, fairly recent archaeological finds cast doubt on T. Rex's status of largest land carnivore. Some studies suggest that T. Rex was fleet of foot, attaining speeds of 15 to 20 miles per hour, other claim the opposite was the case. But the biggest debate centers on whether Tyrannosaurus was really a predator, or simply a scavenger. While most predators will gladly steal another hunter's meal if opportunity presents itself, paleontologist Jack Horner believes that fossil evidence shows T. Rex to have been a lumbering, clumsy brute, poorly-equipped for chasing down prey, which it could not even have seen very well given the small size of its occipital lobes. And its ridiculously tiny forearms would have been useless in a fight. Conversely, the ample olfactory chambers would have enabled T. Rex to smell carrion at long distances, and T. Rex was big and ugly enough to scare smaller carnivores away from their kills. To many dinosaur buffs, this is understandably quite a blow to T. Rex's prestige, but they can take some comfort in the fact that the truth may be irretrievably buried with the secrets of eons past (Locke).

Enchanted Learning. 1996-2008. 21 Mar. 2008.

"Sue at the Field Museum." The Field Museum. 22 Mar. 2008.

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"Dinosaur Timeline Gallery." 1997. Dinosaur Corporation. 23 Mar. 2008.

Locke, Robert. "Killing a Legend: New Evidence Paints T. Rex as a Nasty Scavenger, Not a Vicious Hunter.'' Dinosaur Magazine. Discovery Channel. Discovery Communications, LLC. 23 Mar. 2008.