Giganotosaurus: Giant Southern Hunter

The Giant Southern Hunter compared with a human. As you can see, it was truly a colossal predator!
Image Credit: Durbed, https://www.deviantart.com/durbed/art/Giganotosaurus-carolinii-290866454

In the issue of Empire magazine (released 9th of April 2022), Colin Trevorrow; director of the upcoming film “Jurassic World: Dominion”, talks about the appearance in the film of a Giganotosaurus. He describes Giganotosaurus as “like the Joker” in that “it just wants to watch the world burn”, referencing a quote from the Christopher Nolan film “The Dark Knight”. This didn’t fill me with high hopes for this dinosaur’s portrayal in the film, and instead symbolizes a problem the Jurassic franchise has had since Jurassic Park III; dinosaurs being portrayed as movie monsters, rather than as animals. If any dinosaur started acting like the Joker in behaviour, then it wouldn’t sit well with me because it is applying “human” traits (albeit those of a psychopathic clown!) onto an animal. The animal kingdom can be full of what we might consider dark, cruel and disturbing behaviour. However, there is a difference between giving an animal traits that are plausible based on how the natural world is, and traits that are just not realistic to what an animal would do. I bring this up not to be the stereotypical accuracy obsessed paleo nerd moaning about dinosaur portrayals in popular media (that deserves a blog article of its own). Instead, it is to show why it’s important for any media that communicates palaeontology to have animal behaviour, even speculative ones, that is plausible; people will watch it and believe that what they’re seeing on screen may have at least an element of truth. For example, AppleTV+’s Prehistoric Planet, while being a documentary series rather than a blockbuster film, also has speculative behaviour. But what it does well is that it is behaviour that has a basis in nature (and especially in the animals closest living relatives). Furthermore, it’s behaviour that stems from animals just trying to survive, rather than from more human like motivations. Since a lot of the mainstream publics exposure to dinosaurs is through the Jurassic Park/World series, any unrealistic behaviour that’s shown in these films going to be more embedded into the public consciousness. So, people may come away with thinking that Giganotosaurus was psychopathic. A monster, rather than animal.

So, to link this rant with this blog article, what would the real Giganotosaurus have been like?

Giganotosaurus carolinii (meaning “Carolini’s Giant Southern Lizard, named after it’s discover, the fossil hunter Ruben Dario Carolini), was a large theropod dinosaur that lived roughly 99-96 million years ago in the Patagonia region of Argentina, South America during the “Cenomanian” stage of Late Cretaceous. Its fossils were first found in 1993 and later described in 1995 by Coria & Salgado. These fossils showed that Giganotosaurus had a relatively low skull, robust hind limbs and vertebrae, a reduced shoulder girdle and slightly less forward-facing eyes compared to other large theropods. Furthermore Giganotosaurus and its close relatives (but unlike other large theropods such as Tyrannosaurs), possessed three fingers on each hand rather than two. Giganotosaurus’ skull was also proportionally large compared with its body and was truly massive even for a large theropod (with estimates of up to 1.95 metres long!). You might think such a large head would’ve been a burden, but it was supported by huge neck muscles and had openings in the skull bones, called “fenestrae”, that lightened the skull without sacrificing strength. Also, just like other dinosaurs Giganotosaurus would’ve had a system of air sacs spread throughout its skeleton. These lightened the bones further while also allowing for an extremely efficient, bird like respiratory system where air passed from the lungs into the air sacs during inhalation, then passed from them back through the lungs on expiration, ensuring that a higher proportion of oxygen can be extracted, therefore more is available for aerobic respiration and therefore more energy is available to fuel its metabolism.

A skeleton of Giganotosaurus carolinii on display at the Fernbank Museum of Natural History in Atlanta, Georgia.
Image Credit: Jonathan Chen, https://commons.wikimedia.org/wiki/File:Giganotosaurus_at_Fernbank.jpg

Giganotosaurus belonged to a group of theropod dinosaurs known as the Carcharadontosauridae. These medium-large theropods were generally among the largest land predators around during the early, mid and early stages of the Late Cretaceous, and have been found in most continents, including Africa, North America and Asia as well as South America. The group eventually went extinct sometime in the Late Cretaceous (roughly 80-85 million years ago), with climatic changes playing a role in their downfall. One other suggested theory for their extinction was that they were outcompeted by newer large theropods, with the Tyrannosaurs being one such group. This is not thought to have been the case anymore, with the incredibly short armed, blunt faced Abelisaurs and the long limbed, large clawed Megaraptorans in the south, and the famous Tyrannosaurs in the north instead growing larger and taking advantage of the open niches left vacant by the Carcharadontosaurs.

This Tyrannosaur connection goes further when it comes to Giganotosaurus. When it was revealed to the world via the Coria & Salgado paper in 1995, Giganotosaurus instantly made headlines as theropod dinosaur that was bigger than Tyrannosaurus rex! As a result (since Spinosaurus fossils other than the ones destroyed in World War Two had yet to be described) this made Giganotosaurus the largest known theropod dinosaur at the time. However, there are always caveats with grand statements like this. The chance that any animal will fossilise is incredibly small. Giganotosaurus itself is only known from two partial individuals out of a total population that likely numbered in the tens to hundreds of millions across the entire existence of the species. Therefore, we barely have a minute sample of the total population. So, whilst Giganotosaurus was colossal, with size estimates ranging from 12.5-13.2 metres long and weights between 6-8 tons, it’s hard to say whether this was an average size for this species or not. We may not have discovered the largest Giganotosaurus, just as we may have not found the largest T. rex. So it’s hard to say which animal was bigger based on our small sample sizes. But from what we DO have, on average Giganotosaurus may have been slightly longer, but T. rex was generally heavier. Since mass is often more important when it comes to judging who’s “bigger” (more mass = more muscle and power), T. rex might have been the bigger animal on more occasions. But, this can easily change as more fossils are discovered! This conclusion is further helped by the discover, after Giganotosaurus had been described, of “Scotty”; a Tyrannosaurus bigger than any previously known T. rex specimen. But not to worry Giganotosaurus fans, there would have been size variation within both species. So some Giga’s may have been bigger than some Rexes. This argument also applies to the largest sauropod dinosaurs. Argentinosaurus is considered by many to be the largest sauropod (and largest land animal) that we know of, but there is a lot of overlap with other large sauropods like Patagotitan and Maraapunisaurus. Also, as a quick side note, there’s a trope in media and with dinosaur fans (and I’m guilty of this too!) where any new supersized theropod is always compared to T. rex! There’s no doubt that T. rex is a superstar, but it’s a little annoying that it’s always this benchmark, and that any new theropod that’s even remotely close in size has to be compared to the Rex rather than known purely as its own thing.

A large body size was vital for Giganotosaurus as it allowed it to hunt the big Sauropod Dinosaurs that it lived with, such as the Titanosaur Andesaurus. However despite this, even one Giganotosaurus might not have been enough to take an adult on. So, like any large carnivore Giganotosaurus may have focused on sub-adults, or already weakened adults, or gone after smaller dinosaurs, and scavenged if the opportunity arose. If, that is, it was alone! Fossils of a very close relative of Giganotosaurus (also discovered in Patagonia from slightly older rocks) named Mapusaurus, have been known from multiple individuals of different ages that appear to have been buried together at the same time and place. This has led some to suggest that it, and potentially Giganotosaurus, hung around in groups. So if this giant carnivore wasn’t intimidating enough, imagine a whole group of them! The numbers would have helped to even the odds when hunting giant sauropods. Giganotosaurus was also equipped with sharp, slicing teeth that were like steak knives, perfect for slicing through chunks of flesh and causing, as some documentaries would say, “shock and blood loss”. Furthermore, it’s strong forearms and sharp claws would enable it to grip larger prey, supporting it as it bit and slashed at them. It wouldn’t have hunted just sauropods though, with South American iguanodontid dinosaurs also being on the menu. These could be sprightlier than a sauropod, but Giganotosaurus has been calculated (in Blanco & Mazzetta 2001) to have been capable of reaching speeds of up to 14 metres per second (roughly 31 mph), which is roughly the same as a Grizzly Bear. This would’ve been more than enough, combined with surprise (or at least, as much surprise as a near 13 metre, 6-8 ton giant could get!) to ambush and kept up with its prey. Furthermore, even if the initial attack didn’t finish the job those slicing teeth would inflict deep wounds. The resulting blood loss would weaken the prey considerably, so all a Giganotosaurus (or a group/mob/gang of Giga’s) would need to do is follow and wait.

A close up of Giganotosaurus‘ enormous head, from the same Fernbank Museum skeletal mount. Note the multiple blade like teeth.
Image Credit: James Emery, https://www.flickr.com/photos/emeryjl/3583031860

The idea that Giganotosaurus might have run around in groups raises interesting questions. What would interactions between Giga’s have been like? First off, if they did hunt in groups, it is unlikely that Giga’s would’ve been co-ordinated pack hunters, nor that they had a pride like social structure as Lions do. Just because large carnivores are found buried together doesn’t necessarily complex social groupings, neither does it indicate they had the co-operation to plan lion-like hunting strategies. Instead, it’s more likely they would’ve been more like congregations of Komodo Dragons, Crocodiles or certain Birds of Prey; opportunistic joining together to gang up on prey, but with no co-ordinated strategy. As such when it came to feeding there may have been a free for all! This is where large size would’ve helped. Larger individuals can throw their weight around and intimidate other Giga’s into backing off a juicy part of the carcass, or one that’s being scavenged by another Giga or other large predator. Larger size may also have been a factor in males warding off other males, or females intimidating other females, for the right to attract a mate, with a larger body size equaling a more fit, healthier and therefore more attractive partner. It must also be remembered that even huge carnivores like Giga’s would’ve started as smaller, less able youngsters. Parental care within large carnivorous dinosaurs is often somewhat speculative, as unless there’s a bonebed that preserves multiple individuals of different ages (as has been found with some Tyrannosaurs) or a trackway containing a mix of adults and juveniles together we can only make educated guesses for any animal. In the case of Carcharadontosaurs like Giganotosaurus, as an enthusiast, my own educated guess is that there possibly was some parental care initially (as seen in birds and crocodilians) but then the young would eventually have to fend for themselves. Adolescent Giga’s, being smaller than the adults, likely focused on smaller dinosaurs, the babies of larger dinosaurs, and smaller reptiles and mammals as they were too small to take on giant sauropods. In this way the adolescents would’ve filled a different ecological niche from the adults; the role of medium sized “mesopredator”. Alternatively they joined a gang of adult Giga’s on occasion, picking up the scraps initially inbetween the larger adults. Or maybe they did a mixture of both! These are just ideas I’m throwing around, but maybe in the future there will be an exceptionally preserved fossil or trackway that will give more insight into their behaviour.

Giganotosaurus isn’t the Joker, but an extinct animal whose size and predatorial abilities have made it well known among the paleontological community. Soon, as a result of “Jurassic World Dominion” and other future paleo media, it will be more well known among the general public too, for better or worse!

A scale comparison of some of the largest mega theropods. The Giganotosaurus used in this is on the larger scale compared to the T. rex, which based on the “Sue” specimen (though we now have the even larger “Scotty” specimen). However this T. rex may have been just as if not heavier and there is a lot of overlap between the two!
Image Credit: KoprX, https://commons.wikimedia.org/wiki/File:Longest_theropods.svg

References/Further Reading

• Coria & Salgado 1995, the paper that described the first known fossils of Giganotosaurus carolinii, which had been unearthed 2 years prior.

https://www.nature.com/articles/377224a0#citeas

Coria, R., Salgado, L. A new giant carnivorous dinosaur from the Cretaceous of Patagonia. Nature 377, 224–226 (1995). https://doi.org/10.1038/377224a0

• Calvo & Correa 1998, a follow up paper describing a second specimen of Giganotosaurus that was roughly 8% bigger than the holotype (i.e., the reference specimen that is used as the example of that species and is the specimen all new discoveries are compared to).

https://www.researchgate.net/publication/40662857_New_specimen_of_Giganotosaurus_carolinii_Coria_Salgado_1995_supports_it_as_the_largest_theropod_ever_found

Calvo, Jorge & Coria, Rodolfo. (1998). New specimen of Giganotosaurus carolinii (Coria & Salgado, 1995), supports it as the largest theropod ever found. Gaia. 15.

• Blanco & Mazzetta 2001 paper that evaluated the cursorial abilities of Giganotosaurus.

https://agro.icm.edu.pl/agro/element/bwmeta1.element.agro-article-78acb920-1953-4e1e-85e5-a2ae1686dc49

Blanco, R. E., & Mazzetta, G. V. (2001). A new approach to evaluate the cursorial ability of the giant theropod Giganotosaurus carolinii. Acta Palaeontologica Polonica, 46(2).

• A blog post on fossilera.com by Ashley Strack which gives a wonderful outline of Giganotosaurus, including its discovery, paleobiology, behaviour and more!

https://www.fossilera.com/pages/giganotosaurus-cretaceous-terror-of-argentina

Strack, Ashley, “Giganotosaurus: Cretaceous Terror Of Argentina”, FOSSILERA, www.fossilera.com, https://www.fossilera.com/pages/giganotosaurus-cretaceous-terror-of-argentina

• The Prehistoric Wildlife fact page on Carcharadontosauridae.

http://www.prehistoric-wildlife.com/articles/carcharodontosauridae.html

Prehistoric Wildlife, “Carcharodontosauridae”, Prehistoric Wildlife, www.prehistoric-wildlife.com, http://www.prehistoric-wildlife.com/articles/carcharodontosauridae.html

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