For a time, Tyrannosaurus Rex was the undisputed king of dinosaurs. At the time of its discovery in 1905, there was simply nothing comparable to it; a bipedal monster, as heavy as an African elephant but twice as long, and with teeth that are comparable in size to bananas, Tyrannosaurus seemed to have been by far the largest carnivorous dinosaur ever found. For the next hundred years, there were multiple claims of larger carnivores coming out of northern Africa; however, all proof of their existence managed to disappear, leaving nothing but a few notes and a photograph to show for it. Then, in 1995, a challenger for the crown previously occupied by Tyrannosaurus emerged from the fossil rich beds of Patagonia, Argentina. Named Giganotosaurus Carolini, it immediately made a claim as the largest predatory dinosaur, and has led many to speculate as to who is the most effective predator; Tyrannosaurus or Giganotosaurus? In this article, I will attempt to reach a conclusion based on size, speed, as well as physical adaptations and social behaviors. Of note, this is not about who would win in one-on-one battle! Rather, I am exploring which dinosaur is the most effective land-based killing machine of their time.
Size plays a large part in the dominance an animal has over its respective ecosystem. For both Tyrannosaurus and Giganotosaurus, their sheer size allowed them to be the top predators in their respective food chains with little competition from other carnivorous dinosaurs. But who was bigger? Well, in terms of length and height, they weren’t very far apart. Both animals would have been around 12 meters (40 feet) in length, with Giganotosaurus being slightly longer, topping out at 13 meters; and both would have been around 6 meters (20 feet) tall. With little difference in body size, it would seem as though they were fairly matched; however, a crucial difference between the two lies in their respective weight. Most complete Tyrannosaurus fossils are estimated to have weighed around 7-8 tons, with the largest specimen clocking in at 10 tons, or about the weight of 4 white rhinoceros. On the other hand, the weight of Giganotosaurus has fluctuated throughout the years; while the original specimen was believed to be in the same weight class as Tyrannosaurus, at about 8 tons, estimates that are more recent have suggested it could have been a gargantuan 15 tons, far and away bigger than even the largest Tyrannosaurus. Despite having the same proportions, Giganotosaurus is clearly the heavyweight in this matchup of deadly killers.
Speed is one of the hardest attributes to determine within the field of paleontology. There are no living, non-avian, dinosaurs alive today, making it difficult for paleontologists to assign a speed to a given animal. So how do they do it? One of the most frequently used methods involves building a realistic model of the animal in question, taking into account muscle proportions, bone density and fragility, as well as a variety of factors around the physical attributes of a species. Using this model, the speed of Tyrannosaurus is estimated to be only 19 kilometers per hour (12 miles per hour); if Tyrannosaurus had gone any faster, its bones would have shattered due to the stress put on them. Meanwhile, the speed of Giganotosaurus has been estimated to be about 50 kilometers per hour (31 mph), much faster than Tyrannosaurus. It should be noted that the studies on Tyrannosaurus are more in-depth and realistic than those done on Giganotosaurus; so for now, we must call this one even, as the results are largely inconclusive.
The hunting methods used by Tyrannosaurus and Giganotosaurus can help us in establishing who is the more effective killer. To compare the two, let’s look at each predators bite force; methods they used to “dispatch” their prey; and whether or not they were active predators. When examining the skull of Tyrannosaurus, the word that comes to my mind first is Power. The Teeth, which could grow to a massive 30 centimeters, were cylindrical in shape, and blunt on the end of the tooth. The bones of the skull are 
fused together in many different regions, particularly the nasal bone (located at the front of the skull) which allowed Tyrannosaurus and its close relatives to possess a bite force unlike any other carnivorous dinosaur. Recent studies showed that Tyrannosaurus could bite as hard as 12,800 pounds per square in inch. To put that into perspective, that force is the third largest of any animal, living or extinct (trailing only the giant crocodile Deinosuchus and the largest shark of all time, Carcharocles Megalodon), and is strong enough to bite through a car! Many finds have documented the strength of Tyrannosaurus’ bite, mainly bones of hadrosaurs (duck-billed dinosaurs) that have been punctured by the teeth of Tyrannosaurus (more on this later). These adaptations make it clear that the killing strategy of Tyrannosaurus was simple; use those massive jaws to crush the skeleton of your prey, effectively killing it within seconds. This makes sense, as some of the prey of Tyrannosaurus were heavily armoured, such as the horned dinosaur Triceratops and Torosaurus (which may be the same animal, but that is a topic for another blog article) as well as the armoured dinosaurs Ankylosaurus and Denversaurus. But was Tyrannosaurus really an active hunter? Or rather, a slow lumbering scavenger, only using its massive size to scare away other predators, giving it a free meal? The evidence points towards Tyrannosaurus being an active killer, based on a few facts. First, Tyrannosaurus had very heightened senses and mostly forward-facing eyes; a feature that is usually found in active predators such as hawks and eagles (relatives of Tyrannosaurus). This adaptation gives predators an accurate sense of depth, which is crucial when it comes to tracking moving prey. In addition to advanced vision, Tyrannosaurus also had highly developed senses of both smell and hearing; allowing it to detect prey from quite some distance away. The second, and most crucial variable, is that there is fossil evidence of prey animals surviving attacks from Tyrannosaurus. The first comes from the skeleton of an Edmontosaurus, that shows a bite on its tail from a Tyrannosaurus that had healed; in other words, it survived that attack, and lived long enough to be able to heal properly. Another example comes from the skull of a Triceratops, in which both of its horns, as well as part of its frill, had been bitten by a Tyrannosaurus but healed. Both examples show that Tyrannosaurus was an active predator, not the lumbering scavenger some believe. In addition, it’s more than likely that Tyrannosaurus hunted its prey in packs. Close relatives have been found in mass burial sites that contain individuals of all ages, clearly demonstrating pack-hunting behaviors, or at the very least, that multiple individuals lived and died together. It is possible that Tyrannosaurus hunted in family groups, with the lean and fast juveniles chasing the prey into the waiting jaws of the adults. Based upon these factors, it’s clear that Tyrannosaurus was a formidable killer; but was it more effective than Giganotosaurus?
The skull of Giganotosaurusis a far contrast from that of Tyrannosaurus. Its teeth were sharp and serrated, and rather thin compared to that Tyrannosaurus. The skull is lacking the reinforced and fused joints that are found in Tyrannosaurus and its bite force reflects that difference (estimated to be only one third of Tyrannosaurus’s). Instead of crushing its prey, Giganotosaurus employed a slash and dash strategy; it took a bite out of its prey, letting them either bleed out or live to fight another day, which is far more primitive than the methods used by Tyrannosaurus. This difference is due in part to the fact that Giganotosaurus fed on less armored, but much larger, prey than Tyrannosaurus.
The prey animals that Giganotosaurus fed on were often far larger than itself, such as the long-necked dinosaur Andesaurus, which may have weighed as much as 70 tons when it was fully-grown! Through its slashing bite, Giganotosaurus could effectively take chunks from its massive prey, using as little effort as possible to prey on such a large beast. In addition, it would have been able to dispatch smaller prey animals, including iguanodonts and smaller sauropods that were common in the area that Giganotosaurus hails from. Unlike Tyrannosaurus, Giganotosaurus was not particularly intelligent, and did not have highly developed senses; its sense of vision, hearing and smell were far from that of Tyrannosaurus, so it would have been limited in its ability to track its prey. On the other hand, it was similar to Tyrannosaurus because it too likely hunted in packs, as its close relatives have also been found buried together as well. While not enough material of Giganotosaurus is known to say for sure, it’s completely plausible that Giganotosaurus hunted in packs as well.
Here are the facts. We know that Giganotosaurus was bigger and heavier, and hunted larger, but easier prey. Both dinosaurs hunted in groups and were active killers that went after live prey. We know that Tyrannosaurus had a much stronger and deadlier bite, as well as more developed social structures, senses and intelligence. So, who wins? Well, based on the facts that we know at this time, I believe that Tyrannosaurus comes out on top as the more sophisticated and advanced killer, despite its smaller size. Even though recent finds, such as Giganotosaurus, have tried to dethrone T Rex as the largest predatory dinosaur, Tyrannosaurus Rex still “rules the roost” in terms of who was the superior killing machine in the dinosaur kingdom.
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