Reptile History
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T Rex Dinosaurs

Of course many of us believe that the greatest dinosaur that ever lived was good ‘ol T rex. So this link on our museum site will just be about Rex. First let’s say that no one really knows that much about Tyrannosaurs rex or “the king of the tyrant lizards.” Why is that?

Simply put because he or she exists no longer on our planet. That may be good or most of us would be called snacks and a few big brats (mac’s?). So all we can do is make educated guesses from the few dozen partial skeletons that we have found fossilized. How much can you learn from a rock?

Actually, quite a lot when put together with other evidence such as fossilized track-ways, other dinosaurs fossils that show interactions with Rex (such as teeth marks), coprolites (fossilized doo do), deductive guesses by trained and untrained paleontologists, and comparisons with other related ancestors (such as Albertosaurus) and modern reptiles.

One of the best descriptions of a T rex has been attributed to noted paleontologist Robert Bakker who called it “The Road Runner from Hell.” This is fairly accurate. In addition we know that the closest living relatives are Birds and Crocodiles. By comparing these two species we can get a very good idea of what the T rex may have been capable of.

The following pages and links will be a compilation of many of the thoughts on the museum’s name sake dinosaur. Remember, this is edutainment so if there are some errors, disagreements, and other opinions; that is all part of the learning process.

TYRANNOSAURUS REX: KING OF THE TYRANT LIZARDS

T. rex lived during the Late Cretaceous, some 70million years ago. It was one of the last living dinosaurs before the great extinction event.  It lived primarily in relatively-flat floodplains habitats.

The largest of the tyrannosaurids, it reached an awesome adult length of 50 feet (15 meters), a height of 20 feet (6 meters), and weighed about 7 tons (14,000 pounds).

T. rex was the largest carnivorous dinosaur. An active hunter, it may also have scavenged in order to sustain its substantial maintenance requirements. 

Tyrannosaurus rex is now correctly  portrayed as a sleek, active carnivore,  unlike older depictions as a clumsy tail-dragger.  The massive tail was most likely held off the ground,  serving as a counterbalance  when on the move. This pose was actually proposed many decades ago when the skeleton of the first T. rex (then called Dynamosaurus imperiosus) was mounted in the British Museum of Natural History in London.

T. rex is certainly the most awe-inspiring of all the dinosaurs.  It has been featured in many motion pictures, from "The Lost World" (1925) to  "Jurassic Park" (1993) and  "Jurassic Park: Lost World" (1996).

More thoughts and pics on T-rex

What have been some of the more recent things we have learned or think we may have learned about the T rex? Keep in mind that because we can never know for sure all this information is just theorizing, though often with a lot of science behind it. For every thought on this page you can find some scientist who will claim "It just ain't true." And they may be right. Or then again they may be wrong. This information is presented only to make you think. It is to make you speculate that maybe we don't know it all yet. Keep this all in mind.

  • The average T rex likely weighed in between 5 and 10 tons. But there are indications that there may have been "trophy sized" individuals of 20 tons.
  • T rex may have been able to run at speeds up to 35 miles per hour. That is as fast as a horse. It may very well have simply chased down its prey rather than ambushed it.
  • On the other hand the bite from a large individual would have taken out a piece of living meat from its prey that was over 3 feet long and one foot wide and deep. Whatever got a bite like that would not likely live and may simply have died of shock or blood loss. This would allow the rex to walk up and leisurely finish his or her meal.
  • Even though Tyrannosaurus was quite large his anatomy says he was very agile. Most of his prey were armored and fast. To compensate he would have to be even faster and more agile. While it seems odd, it was very possible that T rex could lunge, jump off the ground (as in dodging Anklysaurs tails), and even roll on the ground to get to or away from dinner.
  • Since any kind of fight by a rex with another of its kind would likely have ended in serious injury or death, they may have used ritualized combat. Instead of biting they may very well have head butted and shoved their opponent around. Rattlesnakes and cobras neck wrestle and try and throw the other down. The weaker of the two usually know it after just a few minutes and leave. rex's may have evolved a similar type of less than lethal combat.

The teeth of the tyrannosaurs

by William L. Abler.
Scientific American, pp. 50-51, September 1999.

Many attempts have been made to answer the question of whether tyrannosaurs were active predators -- seeking out and killing their prey or were scavengers, waiting for the opportune moment to step in and satisfy their hunger. Joining this debate, researcher William Abler and his colleagues have literally looked inside this amazing dinosaur's mouth for clues and come up with some surprising results.

The enormous teeth of the tyrannosaur would seem like the perfect killing tool with sharp points and serrations on both the front and back edges. But when put to an actual test of bone crushing and flesh tearing, would they live up to this perfect image?

Abler and his associates wondered about the serrations seen on the teeth, and whether they would serve the same purpose as those on common kitchen knives. Since no studies had been done regarding knife edges, Abler set up an experiment with serrated blades and tyrannosaur tooth edges.

By creating a series of standardized knife edges, including a serrated edge, the scientists were able to study cuts or tears on actual pieces of meat and simulate biting experiences similar to those that might have been demonstrated by the dinosaur.

The blades were "mounted on a butcher's saw operated by cords and pulleys" that created a sawing action on several same-sized pieces of meat. While the straight edge split the meat, a serrated knife edge "gripped and ripped" it.

A serrated fossil tooth of the ancient shark Carcharodon megalodon produced similar results. When a tyrannosaur tooth was placed in the mechanism, it produced cuts similar to those made by a smooth knife blade that was in need of sharpening. Questioning these results, Abler wondered: if the menacing tooth edges were not sharp, what were they for?

When comparing the serrations of the tyrannosaur tooth with those of the ancient shark, Abler saw major differences in the shape of the points and in the spaces between the points, or cella. The shark's tooth had pyramidal-shaped points. while those of tyrannosaurs were cube-like.

Putting the teeth of Albertosaurus to the meat test, the scientists discovered food particles and grease trapped in the cella. According to Abler, when such particles remain in the mouth they become the sites for septic bacteria which can result in fatal bites to victims.
This indicated that tyrannosaurs might have been able to merely bite their victims and sit back and wait for them to succumb to the fatal infection.

A "puncture and pull" method of biting seemed most apparent to Abler, where the dinosaur's teeth acted as pegs that more or less held the victim. Also, due to the non-articulating surface of the teeth, he hypothesized that tyrannosaurs did not chew their food but swallowed it whole.

Abler cites a study of the Indonesian Komodo dragon (Varanus komodoensis), whose teeth are similar in shape to those of tyrannosaurs. Ciofi's study has led the paleontologist James O. Farlow to suggest a positive comparison between the two animals. Since the Komodo dragon sometimes hunts by biting its prey and then waiting for it to die through an infection of the wound, why wouldn't this be possible in tyrannosaurs?

[People bitten by a Komodo dragon more frequently die from sepsis than from the damage inflicted by the wound itself. -- Ed]

Abler adds that with tightly closed lips, tyrannosaur teeth may have pierced their own gums, which would then have bled and nourished the septic dental bacteria. This would have provided perfect conditions for poisoning future prey.

Breathing life into Tyrannosaurus rex
by Gregory M. Erickson
Scientific American, pp. 42-49, September1999

With an interest in form and movement of the vertebrate animal -- and particularly how these are expressed in the T. rex -- paleontologist Gregory Erickson delves deeply into the predator/scavenger theories associated with this animal, taking a somewhat different tack than Abler, whose study is also presented in the same issue of Scientific American.

Not being one who is satisfied with the idea that function follows form, Erickson includes himself in the "new breed of scientists" known as paleobiologists (Just as the Samasaurus rex is a "paleoethnoherpetologist) . These scientists take the seemingly hard route in searching for explanations for movement not related exclusively to the animal's anatomy.

For this new breed of scientist, clues can be found in sites where groups of dinosaur fossils are found together, in bite marks on bones, and surprisingly -- in coprolites (dino dung)! Using data from the early Tyrannosaurus along with others with similar life styles, such as Albertosaurus, Gorgosaurus and Daspletosaurus, greatly helps the investigation.

When small congregations of T. rex were found together in a site, as was the case in the Hell Creek Formation in eastern Montana, scientists wondered about possible group dynamics of these creatures. Then when a group of albertosaur specimens, presumed comparable to tyrannosaurs in social behavior, were recently rediscovered, they knew they would have a chance to do a more in-depth study.

Paleontologist Philip J. Currie and other scientists from the Royal Tyrrell Museum of Palaeontology dove into the examination and came up with some exciting results. Their conclusions refuted the scavenging theory when they found no evidence that the animals had congregated to take advantage of a mud-hole-stranded, or otherwise trapped, herbivore.

Instead, Currie hypothesized, the albertosaurs were most likely a family group that had been killed in some sort of natural disaster. This kind of information has helped to lay the groundwork for determining social behavior of tyrannosaurs as well.

Another study by Currie and Tanke discusses bite marks made by fighting between theropods, including T. rex. The dinosaurs would have bitten each other, with heads at the same level, using the sides of their mouths rather than attacking from the front.

Bite marks discovered on a pelvis of an adult Triceratops identified by Erickson in 1992 became the "first definitive bite marks from a T. rex". Erickson describes the dinosaurs' method of eating as the "puncture and pull" technique, as does Abler, but does not think food was swallowed whole.

In testimony to this he cites a recently discovered 44 cm long coprolite, presumed to be from a T. rex, containing a large amount of chewed and digested bone.

With all this information in hand, however, researchers are still divided on whether or not T. rex was a predator or scavenger. Erickson points out that all sides can agree on the idea that many animal species obtain food in both ways (e.g., the modern lion and spotted hyena), and that this is a possibility for T. rex.

This same behavior is seen in T. rex's relationship with a common herbivore of the Cretaceous. T. rex bite marks found in an Edmontosaurus bone bed testify to the theropod's scavenging behavior, while its predaceous bite marks can also be found on the healed-over tail vertebrae of an Edmontosaurus that escaped attack. The debate continues.

 

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