Text by David Burnham and Terry Wentz
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Stan T. rex's.... Story.....Skull
Tyrannosaurus rex , the "Tyrant Lizard King", was the largest predator ever to stalk the land. T. rex is known from just over a dozen incomplete fossilized skeletons, which were found in ancient sediments 65 million years old. It was a powerful, agile, bipedal dinosaur, which reached lengths of forty feet, weighed more than six tons and had a five foot long skull. Its enormous, muscular legs would have put it thirteen feet tall, just at the hips. The arms were strong, but ridiculously small and were probably used to grasp onto prey, somewhat like a "meat-hook".
T. rex was also specially equipped with a skull enhanced for prey-capturing: an elongated snout provided an acute sense of smell; large eyes looked forward to allow for prey-tracking 3-D vision; and a ferocious toothed-jaw apparatus designed for a bite, rip, tear, and swallow method of eating. With nearly sixty huge, powerfully-constructed teeth set in a flexible skull, a shearing action of the upper jaws overlapping the lowers gave Tyrannosaurus the capability to devour huge chunks of meat and bone at once.
Teeth were the essential components for killing and feeding, personifying Tyrannosaurus rex. The teeth were specialized for each different tooth-bearing element in the skull and also for their position in that bone. Therefore, the teeth ranged in size and shape, with the path of the serrated edge differing according to the tooth's position in the skull. The large teeth measured up to twelve inches long (root and crown), while the smaller back teeth were only about half as long.
The teeth were composed of dentine with an enamel-covered crown. The crown was the "working portion" of the tooth, while the long root anchored the tooth solidly in the jaw. The serrations in the enamel, along with the strength of massive jaw muscles, gave the tooth cutting power. The dentine of the tooth increased in thickness from the bottom of the root, where it was thinnest and hollowed for nerves and blood vessels (pulp cavity), to solid dentine at the tip of the crown. This dense, blunt tip allowed for a great amount of wear and the "hollowness" of the pulp cavity actually made it stronger.
Tyrannosaurus rex replaced its teeth constantly; each tooth perhaps every few years. The replacement tooth grew inside the jaw alongside the root of the functional tooth on the tongue-side of the jaw. A full-sized, but very thin crown formed first (the "germ" tooth) and it grew by adding layers of dentine. This growth applied constant pressure to the functional root, causing it to slowly become resorbed ("dissolved"). In this way, the replacement tooth actually pushed itself inside the old root, thereby taking its position within the socket. This weakened the tooth enough for the crown to be broken off during feeding. The replacement process was continuous, which ensured the dinosaur was always fully armed.
The Black Hills Museum of Natural History Exhibit
Black Hills Institute of Geological Research, Inc (BHIGR)
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