Nightmare from the late Cretaceous:
Carrying up to eight tons of bone, muscle and teeth, Tyrannosaurus Rex is the embodiment of predatory power from the earths distant past. Forty feet long from nose to tail tip, standing up to twenty feet tall with a head nearly the size of a “Smart” car, it is almost impossible to place this awesome creature in the context of our known experience.
One way to visualize a full grown Rex might be to hearken back to the last time you visited a zoo. Remember the giraffe? A full grown bull Rex would tower about five feet over that giraffe, its bulk would be nearly seven times that of the peaceful herbivore.
Tyrannosaurus Rex had powerfully muscled jaws that opened over a four foot span, filled with up to sixty extremely tough, sharp, conical yet serrated teeth; a design perfectly adapted to ripping flesh and crushing bone. These teeth varied in size by location in the mouth, teeth up to 13 inches in length have been found. As is typical of theropod dinosaurs these teeth were replaced when lost or broken, so T. rex was never completely disarmed.
Habitat and range:
Tyrannosaurus Rex was first reported by Paleontologist Barnum Brown who made his discovery in Montana’s aptly named Hell Creek district in 1902. Since then around 30 specimens in more or less incomplete state have been discovered, along with a few fossil footprints and fossilized feces (coprolites).
The number of available specimens is not sufficient to clearly define T. Rex’s maximum range but conclusive finds include much of the western USA and Canada, with finds in Mongolia as well. Tyrannosaurs are known from the late Cretaceous, starting about 85 million years ago and disappearing around 65 million years ago in the great K-T extinction that ended the life of all the dinosaurs, and many other life forms as well.
Tyrannosaurs are believed to have frequented forested areas where their prey, primarily large sauropods could be found and ambushed.
On August 12, 1990 fossil hunter Sue Hendrickson made the find of a lifetime in South dakata, merely the largest and most complete T. rex skeleton yet discovered. Named “Sue” after Ms. Hendrickson, it took nearly 10 years to excavate, clean, preserve and mount the immense specimen. In May of 2000 the world had its first look at Sue. At 40.5 feet in length Sue is the largest Rex yet discovered, and with over 90 of her bones intact she is by far the most complete. So great is the degree of preservation that the attachement points for the tendons, ligaments and muscles are apparent. Science is learning a lot about T. Rex from Sue.
By a ring counting technique through a cross section of Sues bones similar to that used to find the age of trees Sues was found to be around 26 years old when she died. This is currently considerd to be about the upper limit for Tyrannosaurus life span. The cross section also revealed an amazing growth spurt in Sues “teen” years, ages 12 to 18; she grew at a rate of 4.5 pounds per day!
An extensive cat-scan of Sues skull revealed a surprisingly avian brain structure, and an overall larger brain capacity than other, larger relatives, like Giganotosaurus. Extensive laser imaging and computer modeling of the skeleton are helping scientists to develop models which once and for all should help determine a Tyrannsaurs potential speed and agility, subjects heretofore of extensive debate.
Hunting technique and prey:
Because there is no fossil evidence that T. Rex was a pack hunter the obvious conclusion is that Tyrannosaurus hunted alone. On the other hand, pack hunting cannot be completely ruled out either, based on the paucity of evidence. It would certainly have been a formidable, voracious pack.
There is a great deal of contension over whether T. Rex was much of a hunter at all. The tyrannosaur was massive, with powerful hind legs that could propel it at speeds ranging from 15 to 25 miles per hour, depending on which source you accept. Its bones were hollow. It is speculated that if T. Rex slipped or missed its footing while running at top speed the result would have been similar to a train wreck for the Rex’s skeletal structure, and it could not have survived such an incident. Certainly it could never break its fall with its undersized forelegs.
Analysis of the T. Rex skull indicates a powerful olfactory sensory system, this would be consistent with the scavenger lifestyle, and yet also of value to an apex predator. T. rex had eyes oriented to the front allowing stereoscopic vision which is again a predatory adaptation.
Fossil discoveries have been found which appear to link tyrannosaurs with both hadrosaur and ceratopsian kills, but it is not conclusive that it was the rex that made the kill. It is possible that the tyrannosaur was an opportunist, killing, from ambush when it had to, eating carrion or driving lesser predators from their kill when the opportunity to do so presented itself. Certainly those fearful, massively powerful jaws were more offensive equipment than a pure scavenger needed.
Did mother Tyrannosaurs care for their young? There is no way to know; no eggs, nests or embryos belonging to T. rex have been found as yet. It seems unlikely that a newborn Rex could have fed itself; on that basis alone it seems reasonable to postulate at least some minimal amount of maternal care.
The K-T extinction was swift and sudden, and effectively exterminated almost all large surface life forms. The best guess of the cause at the present time is a powerful asteroid strike coupled with a nearly simultaneous outbreak of massive volcanism. Tyrannosaurus Rex, despite its size, power, weapons and presumed ferocity had no better chance for survival than did the mildest of herbivores.
There is still a lot to learn:
We just don’t know enough about this fascinating animal, but more discoveries are being made all the time, as they are for all the other great meat eating theropods like Afrovenator and Giganotosaurus. Study of these astonishing creatures will be a fertile field for a very long time.