A Dinosaur Classic

A Dinosaur Classic

Of the more than 350 types of dinosaurs presently known, none has been able to displace Tyrannosaurus rex, the king of tyrant lizards, as the leader of the dinosaur pack. Some species have been more agile, some more clever, faster, or more furious. But from the time that it was first described, in 1905, T. rex has been the supreme being of the Mesozoic.

Generations of devotees of horror films and books have long considered Tyrannosaurus rex their favorite villain. In a memorable scene from the classic monster film King Kong, the 40—foot ape battles with one of the dinosaurs that inhabit his fog—enshrouded island. His adversary, none other than Tyrannosaurus rex, was planning to make a meal of the heroine, the Beauty that Kong the Beast wished to have for his very own. Despite her obvious charms and desirability, the heroine would have been a mere hors d'oeuvre for T. rex, who lived in the midst of many gargantuan plant eaters and dined regularly on any creature it had a mind to.

Against a sound—effects background of the heroine's impressively relentless but ineffective screams, Kong comes to her rescue and kills the dinosaur by ripping its jaws apart. In real life the king of tyrant lizards would have had no difficulty making Kong his next meal. An adult T. rex, over 35 feet long, almost 20 feet high, and weighing seven tons, was the unchallenged superpredator of the late Cretaceous, 75 to 65 million years before the present (mybp).

More recently, when Steven Spielberg chose Tyrannosaurus rex as an archvillain in Jurassic Park, he selected wisely. T. rex was doubtless one of the foremost hunters of the Cretaceous (not Jurassic) Period and was certainly the fastest as well as the largest carnivore that had surfaced thus far. The animal was built for hunting, killing, and eating live prey. So efficient, elegant, and formidable was its body design that nature engineered no improvement during the era of dinosaurs.

Tyrannosaurus rex was the absolute king of beasts during its 10—million—year reign. Its body was built to tackle and subdue the most powerful game around. For over a half—century after its discovery in 1902, scientists assumed T. rex to be a sluggish, lumbering giant that caught and fought its equally slow—motion prey in a quickened walk and was often reduced to scavenging. After all, modern oversized mammals cannot run fast, so how could an even more overgrown, underachieving reptile?

Studies of bones, muscle attachments, and footprints indicate that T. rex was anatomically correct for rapid movement and was probably quite agile. In fact, because of a formidable combination of size, speed, and weaponry, it was more than a match for anything that crossed its path. The muscles of its massive legs guaranteed high speed and endurance, punctuated by powerful kicks. T. rex was certainly the fastest animal for its size that we know of, and its birdlike limb design suggests that a speed comparable to that of a racehorse (30 to 45 miles per hour) was altogether possible. The rest of its body mass was directed to the head, with its stoutly constructed five—foot skull and killing—machine jaws powered by colossal muscles. It could open its traplike jaws a good three feet and, with gigantic serrated teeth three to seven inches long, polish off a cow—sized creature—horns, hoofs, and all—in three or four bites. In fact, its typical mouthful of meat would have been enough to feed a human family of four for over a week!

Recent research on an almost complete skeleton of T. rex suggests that it was warm—blooded. A warm—blooded animal the size of a tyrannosaur would require food almost constantly, and hunger would drive it to be a ruthless hunter. Not unlike the modern shrew, it would have to spend most of its time eating. Awed by the potential of this long—extinct beast, scientists have nicknamed it "Roadrunner from Hell."

Everything about T. rex's body design spelled pursuit and kill. Its limbs tell the scientist that it could move much faster than most other predators. The two—clawed forelimbs were so small they almost appear underdeveloped or on their way to extinction, but most scientists no longer believe this to be true. Since the head of this huge carnivore was so massive, T. rex's weight had to be reduced elsewhere on its front end. Its slender arms appear out of place on the colossal body, but they were far from useless. They were probably strong enough to lift 450 pounds, and the claws of the miniature limbs held the prey like grappling hooks while the jaws did their deadly work.

Several scientists still accept an early theory that Tyrannosaurus rex was a scavenger. The evidence indicates that at times T. rex would scavenge, just as a modern lion or tiger will do. When the food is just sitting there, why not? Fossil remains of a T. rex banquet were found near Alberta, Canada, where scientists have excavated at least 80 triceratops—like animals called Centrosaurus. About 70 million years ago a herd of these Ceratopsian dinosaurs attempted to cross a stream during a high flood. Several hundred of them did not make it and drowned in the raging waters. Their carcasses were washed downstream and piled up on large sandbars. This must have been an invitation for every neighborhood carnivore to a free lunch, and a dinosaurian feeding frenzy took place.

The scientists found many carnivore teeth among the bones, for the meat eaters of the day shed teeth virtually every time they fed. The teeth were replaced by new ones almost before the old ones were gone. Many of the teeth and tooth marks were those of tyrannosaurs, but most scientists now believe that scavenging was not an essential feeding style for the greatest land carnivore that ever lived.

T. rex was doubtless one of the foremost hunters of its day. Whether it stalked its prey or sprang from ambush, the end result was surely the same. One can almost imagine the huge beast springing from the forest and racing toward its chosen victim. What a sight to behold: a massive, menacing monster moving swiftly and with determination, its mouth open a full three feet and displaying innumerable teeth that glistened in the sunlight, while it emitted whatever kind of roar it made. It should have been enough to make the intended victim die from fright.

The tyrannosaur epitomizes the final greatest expression of the evolution of flesh—eating dinosaurs, terrible but elegant in form. In spite of being so efficient at killing and being the undisputed ruler of the Cretaceous world, T. rex fared no better than the dinosaurs on which it dined. With the close of the Cretaceous period 65 million years ago, tyrannosaurs, along with the rest of the dinosaurs, vanished from the face of the earth.

The classic picture of life in the primeval forests and plains of 70 mybp is a battle between the world—class gigantic gladiators of the Cretaceous: Tyrannosaurus rex and Triceratops. Murals, books (including textbooks), and films have depicted this incident so often that it has been the automatic image for anyone who conjures up a vision of the life and times of dinosaurs. Although the triceratops would have been a most impressive adversary of T. rex, until recently there has never been any solid evidence that a tyrannosaur ever ate a triceratops.

Triceratops, among the most abundant of the Ceratopsian dinosaurs to inhabit the lands that would become North America, roamed the plains 75 to 65 mybp in vast herds. They were enormous beasts that grew to lengths of 24 feet and weighed nearly nine tons. Their massive skulls, up to six feet long, weighed at least a ton and were adorned with a pair of four—foot, sharply pointed horns above the eyes and a smaller horn on the tip of the snout. Because the head was perfectly balanced on a pivot joint under the eyes, the neck muscles could toss it in any direction with great precision. When attacked, a triceratops had only to face an enemy, charge, and impale it. Surrounding its skull was a large protective bony shield that extended back over the neck. Broken triceratops horns and shields are common and, along with gouge marks, show that these ancient giants fought among themselves, most likely during mating season. When they collided over the affection of a waiting female, it must have resounded like a clap of thunder.

Armed with enormous jaw muscles, a heavy, parrotlike, beaked snout, and massive cheek teeth, Triceratops could have chewed its way through a tree trunk and probably did just that. And it may have also given the king some painful, appetite—quenching predinner abrasions. Generally these hoof—toed quadrupeds browsed quietly in herds on open plains, snipping bunches of tough plants with their pointed bony beaks and then chewing with scissorlike teeth.

Tracks of Triceratops, probably on migration, always show the young in the middle surrounded by adults. When attacked by a predator they probably formed a protective circle around the young. The sight of a ring of massive lancelike horns protruding from skull shields would have discouraged many a hungry carnivore. Recall a scene of medieval knights on horseback facing an enemy with weapons protruding in front of a wall of shining shields.

Many scientists do not doubt that the tyrannosaur would at times stalk the triceratops to within attacking distance and, with a loud roar, charge at top speed. Very likely the triceratops would turn and try to run away, leaving its flanks and back exposed to the tenacious teeth that could make short work of the exposed body. At times, however, instead of running, a huge adult triceratops would suddenly turn and face the oncoming monster, its four—foot lances poised directly at its adversary. With enormous calf muscles to power a quick charge, and knee—straightening muscles to provide great leverage, Triceratops possessed the agility necessary for a sudden, unerring attack. T. rex would not have time to slow up or to dodge the horns, as the momentum of its great body weight and speed of attack would carry it directly onto the threatening horns. The jungle would reverberate with roars of agony as the horns penetrated several feet into T. rex's body. And the triceratops would walk away from the dying tyrannosaur, unharmed but with very bloody horns.

Until recently, scientists had no shred of evidence that such tyrannosaur—triceratops encounters ever happened. During the fall of 1992 such evidence was finally unearthed. Scientists from the University of California, Berkeley found a large adult triceratops hipbone that was 70 million years old. Several well—defined bites and marks showed where the carnivore's teeth dragged against the bone. To confirm the identity of the biter, the scientists filled the holes with dental putty; the resultant casts were identical with tyrannosaur teeth. Moreover, no other carnivores existing at that time were large enough to make such wounds.

Why was such evidence not found until after almost a hundred years of collecting fossil remains of these species? Considering the prerequisites for an animal to be preserved as a fossil, the chance of preservation for millions of years is incredibly rare. Compare, for example, the millions of bison that covered the plains of North America 150 years ago. Where are the billions of bones that would have been strewn over the area so recently? Occasionally a farmer may plow up an isolated bone, but most have weathered away naturally. Also, tyrannosaurs usually didn't leave much behind after they finished dining. Like modern hyenas, they consumed everything, including the bones. In the case cited above, T. rex must have been so full that it just couldn't swallow another bite!

 

From the book: 
Petrified Lightning