Carcharodontosaurs

Carcharodontosaurs were huge carnivorous theropod dinosaurs that lived during the Cretaceous Period. The type genus was Carcharodontosaurus, a huge Carcharodontosaur from Africa. It also may have been the first predatory dinosaur to raise speculation that there were in fact predatory dinosaurs that grew larger than Tyrannosaurus rex, the predator that was credited as being the largest terrestrial carnivore of all time for the better part of the 20th century.

Later Acrocanthosaurus was discovered, a predator that also showed to be near the size of T. rex. Its size was estimated at over 4.5 tonnes, about as large as three Allosaurus put together and almost as large as T. rex. The first Carcharodontosaur to be fully credited as being larger than T. rex was Giganotosaurus. This dinosaur was represented by relatively complete remains, and scientists feel like it is easier to judge the weight of this animal than that of other predators such as Spinosaurus.

Although Spinosaurus is today often credited as the largest predatory dinosaur ever, because of isolated material it may not be as large as many think it was. Because of the new slimmed-down proportions of this animal, it may have in fact been smaller than Giganotosaurus, and some even suggest that it was smaller than Tyrannosaurus.

Tyrannotitan was also discovered later, a huge predator that may well have weighed slightly more than Tyrannosaurus. Some length estimates even put Tyrannotitan at 15 meters long, although among predatory dinosaurs probably only Giganotosaurus, Oxalaia and Spinosaurus reached this length, and there is no hard evidence suggesting that Giganotosaurus really did get this big.

## Hunting Strategies

Unlike the powerful bites of Tyrannosaurs, the Carcharodontosaurs relied on causing their victims to bleed out. This method may not have been as effective for hunting small prey, because dinosaurs like Tyrannosaurus rex could simply kill their victims with one bite whereas the Carcharodontosaurs would have to deliver multiple bites and then wait for their victims to bleed to death. However, the powerful bite of the Tyrannosaurs would not do enough damage to massive Sauropods to kill them, and the blood loss factor would be less meaning that Tyrannosaurs could not kill large Sauropods if they ran into them.

However, the Carcharodontosaurs were designed to take out these giants by biting them and letting them bleed to death. The teeth of the Carcharodontosaurs were not designed to crush bone, but they were very effective at slicing through meat. There is even evidence suggesting that the Norht American Carcharodontosaur Acrocanthosaurus could kill the huge sauropod Sauroposeidon.

Acrocanthosaurus at least was very heavily built with incredibly tough neck vertebrae and very powerful arm muscles. Scientists estimate these arms to have been able to lift around a tonne! However, these arms were probably not too effective at taking out Sauropods. Acrocanthosaurus probably relied mainly on its bite because the arms could only move around 25%.

Perhaps the most intriguing discovery of Carcharodontosaur hunting strategy was made when paleontologists found several Mapusaurus of different ages buried together. Mapusaurus was around the size of Acrocanthosaurus, and if it truly hunted in packs as this material suggests, it may be able to take out very large Sauropods like Argentinosaurus. This also may help debunk the theory that Giganotosaurus was a scavenger. Like Tyrannosaurus, it was proposed that Giganotosaurus was a scavenger. The reason for this proposal stems from some analysis suggesting that Giganotosaurus' legs were not powerful enough to let it run. If it hunted in packs like its cousin Mapusaurus, this would rule out the idea of scavenging behavior. Tyrannosaurus was also highly unlikely to have been a scavenger because of its large list of predatory specializations that will not be discussed in depth here.

Carcharodontosaurus, the type genus has also been suggested to have hunted Sauropods. This theory has been backed up by some saying that the extinction of the huge Sauropod Paralatitan coincides with the extinction of Carcharodontosaurus. However because of fragmentary remains of the theropod, the exact event that caused its extinction cannot be determined. Not even the correct food source of Carcharodontosaurus is certain. Several other myths about this dinosaur have arose specifically on the internet as a result of the meager material representing it. Many claim that it was of incredibly size and strength, some even that it was larger and stronger than Giganotosaurus. It is certainly amazing how quickly these speculatory statements spread, however they must be taken with a grain of salt because scientists aren't sure how big Carcharodontosaurus truly was. It was most likely much smaller and weaker than many primarily on obscure internet sites believe it was.

Although scavenging may or may not have been a primary food source of the Carcharodontosaurs, they may have sometimes hunted smaller dinosaurs. Acrocanthosaurus likely hunted some smaller hadrosaurs, where some South American Carcharodontosaurs possibly even hunted small sauropods like Amargasaurus.

## Causes of Extinction

Acrocanthosaurus in North America disappeared after the Albian stage of the Cretaceous. This was probably a result of the large Sauropods such as Sauroposeidon disappearing. North America and Asia were the first continents to witness this. In South America, the huge Argentinosaurus also disappeared slightly later, limiting the food of the huge Carcharodontosaurs such as Mapusaurus, Giganotosaurus, and Tyrannotitan. Competiton from the Abelisaurs and the rise of the armored dinosaurs may have also spelled their downfall. Even Titanosaurian Sauropods such as Saltasaurus evolved dermal armor. This new wave of herbivores eventually helped drive the old predators to extinction. In North America and Asia, there was the most dramatic evidence of this. The old dinosaurs had nearly vanished with no Sauropods remaining in North America. Far more advanced armored herbivores meant that the chance of Carcharodontosaurs surviving in these continents was next to none.

In South America, these huge predators were also beginning to meet their downfall. Giganotosaurus remains younger that the Cenomanian have not been recovered, along with all of the other South American Carcharodontosaurs. Towards the end of the Cretaceous, one final colossal Sauropod evolved, the 59,000 kg Dreadnoughtus. This huge herbivore that lived at the Southern tip of Patagonia during the Maastrichtian, the final stage of the Cretaceous, may have provided food for some populations of Carcharodontosaur. In Brazil to the north there has also been evidence of Carcharodontosaurs.

Extinction is a gradual process. It took hundreds of thousands, if not millions of years for the Carcharodontosaurs in North America to disappear. In South America there may have been a few more hanging on as Endangered Species, but did not have the population or adaptability to survive the KT extintion. If anywhere, the Carcharodontosaurs had the best chance of survival in Africa, where many of the older species may have still been around. However, here there were also huge populations of Abelisaurs. For other reasons that still need to be discovered, Carcharodontosaurs in Africa may not have lasted until the later stages of the Cretaceous.