April 4, 2022 Scott Kraus

Tyrannosaurus Rex is a Giant Cretaceous Carnivore

The Tyrannosaurus Rex or “tyrant lizard” is one of the better known dinosaurs of all prehistory. While many believe that this seven ton carnivore was a creature of the Jurassic age, this theropod did not come along until much later during the cretaceous era. When it comes to carnivorous dinosaurs, the tyrant lizard king is one prehistoric reptilian that paleontologists have come to know pretty well.

Quick Facts

 What Did Tyrannosaurus Rex Look Like?

Tyrannosaurus Rex was a Bipedal Saurischian Dinosaur

Paleontologists have a fairly clear picture of the Tyrannosaurus Rex in many aspects based upon skeletal remains, but there are still a number of elements that researchers cannot be sure of. Among those things that remain something of a mystery are the exact weight and size of these giant carnivores. Skeletal remains are enough to give paleontologists an estimated range for this data; however, without tissue and muscle mass and without a large specimen group to study estimates are all we can go by. As a theropod, Tyrannosaurus Rex is both bipedal and Saurischian meaning that it traveled using the rear legs only and that its hips were more lizard than birdlike in construction. The majority of theropods were strictly carnivorous and as such they possessed teeth that were developed for tearing and ripping at flesh. Of all theropod dinosaur species, the Tyrannosaurus Rex is known to be one of the largest of these carnivores with exception to the Spinosaurus and the Giganotosaurus.

Physical Attributes of Tyrannosaurus Rex

One of the most commonly recognized features of the Tyrannosaurus Rex is the incredibly large skull with large backwardly curved teeth. The backward curving of these teeth helped to reduce the likelihood that while feeding or capturing prey this carnivore would lose or damage teeth. Without its large and powerful teeth, the T-Rex would have had no means for feeding since its forelimbs were simply too small to facilitate capturing prey and maneuvering it closer to the jaws. The largest known teeth of a Tyrannosaurus Rex have measured in at around twelve inches long including the root. Not only were these extremely large teeth long but they also featured ridges on the back edge to reinforce them. If feeding was reliant upon the teeth, just what role did the forelimbs of this Cretaceous carnivore play? The small forelimbs which featured only two clawed digits and the remnants of a third, measure in at approximately 3 feet in length have been a subject of speculation for years in the paleontological community. Many believe that the short forelimbs served as a means of grasping a mate while mating and others believe that they were utilized to hold large prey items as they were being shredded by the T-Rex’s teeth. It is possible that both of these hypotheses are correct.

Sexual Dimorphism in Tyrannosaurus Rex

Only one Tyrannosaurus Rex specimen has ever been identified as being definitively female. This assertion can be made definitely as a result of preserved medullary tissue that shows the potential for the specimen in question to develop eggs. Researchers believe that the female T-Rex was generally a larger and more robust specimen with specific developments aimed to improve egg production such as a wider pelvis.

The Senses of the Tyrannosaurus Rex

The Tyrannosaurus Rex is known for its particularly accurate sense of smell, the reason for this lies within the brain of this beast. Paleontologists are able to tell a lot about dinosaurs by creating casts of the brain casing, in the case of Tyrannosaurus Rex, researchers found that this carnivore had a particularly large olfactory processing center. The sheer size of this portion of the brain indicates that T-Rex depended upon its sense of smell rather heavily when it came to hunting down prey. In addition to a large olfactory processing center in the brain, there is also evidence that the Tyrannosaurus Rex had large visual lobes as well. With forward facing eyes, the T-Rex would have had depth perception that assisted in hunting and attacking prey items. The fact that the Tyrannosaurus had particularly keen vision comes as a surprise to many amateur paleontologists who falsely believe that this creature hunted based upon movement. It is not true that this beast could not view prey items that were not moving and there are a number of reasons evident that explain why. Firstly the binocular vision of T-Rex provided sharp vision, a feature that is simply not found in animals with poor movement-based vision. Secondly, with such a developed sense of smell movement would have played very little role in the ability of this dinosaur to track down prey items.

The Feeding Habits of Tyrannosaurus Rex

The Tyrannosaurus Rex had a short muscular neck that was s-shaped and designed to carry the mass of the extremely large skull. While juvenile Tyrannosaurus had a much smaller and shorter skull, as this carnivore grew the skull became much larger and heavier warranting a thicker and more supportive neck. As the skull developed in adolescent and fully grown Tyrannosaurus Rex, the musculature of the jaws also became much more developed increasing the bite force of this beast exponentially. A recent study by Dr. Karl Bates of Liverpool University evidences that the bite of a fully grown Tyrannosaurus Rex could have exerted as much bite force as 10,800 pounds. Researchers believe that the physical changes that occurred as the dinosaur grew, such as skull lengthening and more developed musculature resulted in changes in feeding habits as well. Where the juvenile T-Rex would have been much smaller and more athletic it would have lacked the jaw strength to take down large prey items and may, as a result have fed mainly through scavenging. As the T-Rex grew and developed a much more deadly bite force, but a much slower means of locomotion it would have been forced to feed upon slower moving but much larger prey items like Triceratops.

Locomotion of Tyrannosaurus Rex

Tyrannosaurus Rex is believed to have measured in at approximately 7.2 metric tons, been 42 feet in length and approximately 13.1 feet tall at the hips. The huge body of the T-Rex was carried upon its toes when it walked and its massive feet left footprints that measured over a foot and a half in length. The total foot length of this theropod is estimated to have been just over three feet long. It is a direct result of the considerable mass of this dinosaur that Tyrannosaurus Rex could move at a maximum speed of only 25 miles per hour. It is just as well that this giant Cretaceous beast did not move at speeds much faster because one trip could result in fatal bone breaks. While the huge rear legs of Tyrannosaurus provided plenty of weight bearing capability, the extremely short forelimbs and sheer mass of the body meant that any fall at high speeds would have likely resulted in fatal injuries. T-Rex was also particularly limited in terms of locomotive capability in that the extremely large tail that served to counterbalance the long skull of this beast, served to make maneuvering extremely difficult. Researchers estimate that the Tyrannosaurus was in fact so long that it would have taken a couple of seconds in order to turn a forty five degree angle. These limitations on movement severely limited the locomotion and hence the feeding habits of this cretaceous giant when fully grown.

Reproduction in Tyrannosaurus Rex

While not too much is known about the parenting habits of this giant carnivore, researchers believe that Tyrannosaurus hatchlings would have been co parented. After watching over her eggs until they hatched, the female would leave the young hatchlings in the nest to seek food to replace the nutrients lost after nurturing her eggs. At this time it is believed that the male would be left to watch over the young. It is possible that both male and female would step away from the nest in order to feed leaving the young hatchlings open to predation from any number of larger carnivores and herbivores. It may seem odd that an herbivorous dinosaur would have any interest in a Tyrannosaurus hatchling; however, small hatchlings soon grow in to large predators. Contrary to popular belief, Tyrannosaurus Rex was most likely a caring and nurturing parent with an instinctive desire to continue its genetic lines in its offspring.

The History of Discovering Tyrannosaurus Rex

Naming the Tyrant Lizard King

Tyrannosaurus Rex was named in 1905 by the president of the American Museum of Natural History, Henry Fairfield Osborn. The name was given to this giant cretaceous beast as a means to emphasize the size of the creature since at the time both Giganotosaurus (1995) and Spinosaurus (1915) had yet to be discovered.

The First Tyrannosaurus Discovery

The first paleontological discovery in terms of the Tyrannosaurus Rex was made in 1874 when teeth from this theropod were discovered in Golden, Colorado by A. Lakes. More than a decade later, in the 1890’s postcranial fragments of the T-Rex were discovered in eastern Wyoming by J.B. Hatcher and then in 1892 vertebral fragments were discovered in South Dakota by E.D. Cope. These smaller discoveries paled in comparison to the first partial skeleton of T-Rex that was discovered in 1900 in eastern Wyoming by Barnum Brown. Brown would go on to recover another partial T-Rex skeleton in the Hell Creek Formation in Montana in 1902 and it was this specimen as the holotype for the species. Throughout his career, Brown would go on to find numerous Tyrannosaurus skeletons, a number of which were sold to history museums where they were put on display. The most noted of Brown’s specimens is his Hell Creek discovery that can be found in the New York American Museum of Natural History.

Sue the Tyrannosaurus Rex Specimen

Of all Tyrannosaurus specimens to be recovered, the most well known of all is the Tyrannosaurus known as Sue. Sue was named after Sue Hendrickson, an amateur paleontologist who discovered the specimen in the Hell Creek Formation in South Dakota. Sue is recognized for being the most complete Tyrannosaurus specimen to be discovered. Sue was purchased by the Field Museum of Natural History where her fossilized remains were cleaned completely so that a cast could be made of the skeleton for display. What makes Sue so significant to the paleontological community is that this fully grown carnivore provided more evidence about the life of the T-Rex than was ever known before.

Sue goes down in history for being the longest lived Tyrannosaurus Rex; estimations put her at around twenty eight years old at the time of her death. While Sue was around twenty eight years old, it is believed that she reached her full size at around age nineteen. This information provides paleontologists with important information in terms of the longevity of these giant carnivores in addition to the approximate growth rates that can be used when analyzing other Tyrannosaur specimens. Researchers believe that Sue was killed as the result of a parasitic infection contracted from eating diseased meat, this conclusion was reached after finding tell tale signs in her skull similar to those found in birds with the same parasitic infection. Ironically something so tiny managed to wipe out the longest living Tyrannosaur known to man.

Stan and Jane

Stan and Jane are two other Tyrannosaurus specimens that have been recovered leading to further knowledge about these Cretaceous carnivores. Stan was recovered by amateur paleontologist Stan Sacrison in the Hell Creek Formation in South Dakota in 1987. Stan was only 63% complete but is an interesting discovery due to the various number of bone pathologies that are present in his skeleton. Jane is a juvenile Tyrannosaurus Rex specimen that was also recovered in the Hell Creek Formation by a Burpee Museum of Natural History excavation team. While Jane is only approximately 50% complete she is the most complete juvenile specimen of a tyrannosaurus to have been found to date.

The Importance of Understanding Tyrannosaurus Rex

Of all dinosaur species, the T-Rex may perhaps be one of the most misunderstood of all dinosaurs. With so many falsities floating around about this giant Cretaceous carnivore it is important to understand the truth about this unique and dominating creature. While Tyrannosaurus Rex may not have been the largest of dinosaur species, and it most certainly is not representative of the dinosaur movie goers may recall from the film Jurassic Park, there are a great many interesting facts to learn about this sixty seven million year old species.