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Tyrannosaurus
rex is the best-known and largest member of the group; its
fossils are found in eastern Asia and western North America, where it
lived 65 million–80 million years ago. The “king of the tyrant
lizards,” as its Latin name is usually translated, was undoubtedly a
biped, walking on powerfully developed hind limbs. If the animal had
stood upright, it would have been more than 6.5 metres (21 feet) tall,
but the usual posture was stooped, with the body carried forward and
the tail held off the ground as a counterbalance. In this position a
large adult could measure 14 metres long.
It
has been estimated that a living T. rex could have weighed almost
eight tons. The length of the skull alone was more than 1.3 metres and
provided T. rex with tremendously strong jaws. Fossil skull bones are
often several centimetres thick and are strongly braced to each other,
which suggests a resistance to the forces of biting, both inflicted
and received from other tyrannosaurs. Engineering models, in fact,
show that the animal's bite force would easily have been capable of
ripping through a car roof, as portrayed in the 1993 motion picture
Jurassic Park. The huge mouth contained some 60 teeth, which could
grow as long as 15 cm (6 inches). The front teeth were D-shaped in
cross section, tapering toward the tip. The crowns of the teeth, like
those of all animals except mammals, were shed and regrown frequently
(every 250 days or so, on the basis of microscopic lines visible
within the teeth). Serrations of the teeth bear deep pocketlike
recesses in which bacteria may have flourished to provide an
infectious bite, much like that of the giant Komodo
dragon today.
"tyrannosaur" Encyclopædia
Britannica from Encyclopædia Britannica Premium Service.
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