What is Spinosaurus, and how would it fare in a Spinosaurus vs Carcharodontosaurus confrontation?
Spinosaurus aegyptiacus is an extinct species of theropod dinosaur that lived in what is now North Africa, from approximately 112-93.5 million years ago (upper Albian to upper Turonian stages of the Cretaceous Period). It is without a doubt, one of the most famous dinosaurs on the planet. Much of this fame (or infamy) is the result of its appearance in the 2001 movie “Jurassic Park 3”, where an exaggerated (and grossly anatomically inaccurate) version of it wiped the jungle floor with the most famous dinosaur of all time, Tyrannosaurus rex. Of course, T-Rex never lived with Spino. If anything, it would have been a Spinosaurus vs Carcharodontosaurus (the “African T-Rex”) fight for survival. But not like you see in the movies.
Our knowledge of extinct life is always expanding, and we know now that “Spino” was nowhere near as big, bad, or buff as in JP3. It did not have ninja neck-breaking skills, nor did it spend most of its day running around on two legs like most theropods. Instead, its locomotory method was more like that of a quadruped, with it spending the majority of its time either walking on all fours or swimming. It also had a tall, narrow, fin-like tail that was ideal for propelling it through the water (our eternal gratitude to Ibrahim et al for their fantastic discovery and amazing research).
Now that we know what Spino’s skeleton and silhouette looked like, let’s cover the basic questions first. Then we can explore something that’s been on my mind since word first came out about the villain of JP3 being a slender-snouted quadruped: how did a comparatively “dainty” fish-eater defend itself against one of history’s mightiest predators?
How big was Spinosaurus really, and how much did it weigh?
The latest estimates (Ibrahim et al 2014, Henderson 2018) suggest that, on all fours, Spinosaurus stretched somewhere from 49-52 feet in length (15-16 meters), with a weight in the realm of 7.1-8.3 tons (6.4-7.5 tonnes). That made it approximately the same weight as a good-sized bull African bush elephant. Just keep in mind, Spino was not built like traditional theropods and a large percentage of that length was a long neck and a very long tail. Its size was most likely partly the result of an abundance of protein, with said protein containing “longevity-increasing” nutrition. I am referring to that Omega-3 fatty acid rich superfood: fish. If you doubt this, consider the Alaskan brown bear. Kodiak bears feed largely on salmon, and are both considerably larger and longer-lived then their genetically identical relatives, the Grizzly bear (28 years vs 20-25 years, 660-1,320 lbs. vs 254-794 lbs.). Both are the same species, Ursus arctos, and have only been listed as sub-species due to their differing appearances.
The other factor that likely contributed to Spino’s tremendous size was evolutionary pressure to become larger than any competitors/threats. For example, according to current estimates (O’Brien et al 2019) the contemporaneous crocodile Sarcosuchus imperator, which occupied the same bodies of water as Spinosaurus and most likely hunted similar prey, reached an estimated maximum length of 31.2 feet (9.5 meters) and weighed 4.7 tons (4.3 tonnes). Although juvenile Spinos undoubtedly fell prey to large crocodiles, large adults were likely, by sheer size, relatively immune to predation.
Why did Spinosaurus have a sail?
As it turns out, the sail of Spinosaurus was not unique. Many extinct animals had similar structures, from pelycosaurs like Dimetrodon to dinosaurs like the hadrosaur Ouranosaurus (a contemporary of Spinosaurus) – both possessed “sails” to varying degrees. Interestingly, Spino’s relative, the theropod Suchomimus, also possessed extended neural spines on its back, although its sail was not as pronounced as that of its larger, quadrupedal relative. Suchomimus was also a very large (36-foot, possibly bigger) piscivore, but, as I will discuss shortly, I suspect it being primarily bipedal contributed to it having a less-developed sail. The 38-foot North American macropredatory theropod Acrocanthosaurus also possessed extended neural spines, similar to those of Suchomimus.
I believe these sails were primarily used for the storage of fat, and hence water, as we see in extant camels. When exposed to the rigors of dry seasons, theropods possessing thick, heavy sails that stored a reservoir of fat would find themselves in a highly advantageous position. Their “humps” would provide them with both calories and water, wrung from absorbed fat cells. This would enable the animal to better survive period of drought or famine and pass on its genes. In the case of more mobile, primarily bipedal theropods like Acrocanthosaurus or Suchomimus, the humps didn’t need to be as large, as it was easier for the dinosaur to migrate to areas where food and water was still available. Spinosaurus, however, would have had a harder time moving from a dried up river in search of water and may have, like the extant Nile crocodile, hunkered down in the mud or in an excavated lair and waited for the rains to return. If it did decide to migrate in search of greener (or wetter) pastures, its larger sail would have provided more calories and water reserves to get it where it needed to be.
Lastly, it is possible that Spino’s sail may also have enabled it to remain in the water for longer periods of time. Crocodilians must crawl out of the water periodically to bask in the sun in order to regulate their temperature. With Spino possibly being warm-blooded, it would have lost body heat while submerged, even with gigantism on its side. By keeping its sail above the water and exposed to the sun (dark pigmentation in the sail would have assisted in this – it is also possible that, like many reptiles, it could alter the color of its skin as the need arose, its sail in particular) it could have absorbed solar radiation, warming the blood in its sail and then sending it to the submerged portions of its body. This would have enabled it to stay submerged longer without having to crawl ashore and bask (a potential risk which will be addressed below).
What did Spinosaurus feed on?
Spinosaurus inhabited river systems, lakes and marshes, and with the tall, paddle-like tail that we now know it had (Ibrahim et al 2020), its behavior was probably like that of a crocodile, with it spending most of its time in the water. Its long, narrow skull and sharp conical teeth, sans serrations or carinae (cutting edges) strongly suggests that its diet was fish. There were numerous fish and aquatic animals inhabiting the same ecosystems as Spino, and many were undoubtedly on its menu. This including an assortment of small sharks, turtles, large lungfish, crocodylomorphs, and even the smallish plesiosaur Leptocleidus, which measured 5-10 feet. The largest potential prey items it encountered were the 26.1-32.7-foot (8-10 m) sawfish Onchopristis, and the massive, 16-foot* (5 m) coelacanth Mawsonia. *Note: although Wikipedia lists Mawsonia at only 4 meters, I have a very large post-parietal (skull section) in my collection that suggests the species definitely exceeded 16 feet.
How big of a meal could Spinosaurus eat?
The jaws of Spinosaurus were long and slender, much like those of a false gharial, and were not designed to withstand the torque generated by the lateral movements of massive prey items. Put simply, it was not dragging down ceratopsians (horned dinosaurs) for dinner. Rather, the morphology of its jaws permitted them to flex against vertical pressure (Cuff et al, 2013). Based on these factors, as well as its teeth not having the ability to shear through flesh, but rather being intended to puncture and pin prey items, it is my considered opinion that the dinosaur fed primarily on fish in a size range that it could swallow whole. The roof of its mouth was solid, indicating it was designed to withstand the up-and-down struggles of thrashing prey (i.e. fish), but its skull was not designed to withstand heavy loads when moved laterally (from side to side). This suggests that it would have been difficult for Spino to tear bite-sized hunks of flesh from large, tough-skinned prey items.
My theory on this is further supported by the presence of an “alcove” that exists in the premaxillary of Spinosaurus, along with the existence of a bulbous portion at the end of its mandible that meshes perfectly with it. This is a perfect “fish trap” – one that allowed Spino to keep a tight grip on slippery prey. The implication of this is that the body diameter of most of the fish it targeted fit within the dimensions of that alcove, hence they would be in a size range the dinosaur could swallow. If terrestrial prey items were on the menu (young dinosaurs, hapless pterosaurs, etc.) it is likely that they were also chosen based on size. We see this with gharials, as well as large predatory fish like the extant alligator gar. I’ve fished for gar, and can say from experience that if a bait fish is too big to be swallowed it is typically ignored.
How did Spinosaurus catch its food?
Spinosaurus had numerous adaptations that allowed it to successfully capture its prey. These included a long, muscular neck that had a slight sigmoid (S-shaped) curve to it, a long, narrow snout filled with sharp teeth, an alcove at the end of said snout to better grip fish, and pressure sensors (foramina) lining its maxilla and mandible. The curve in its neck allowed Spino to draw its neck back like a pelican and also enabled it to lash out swiftly, almost like a snake. The narrow jaws were advantageous as well, as they slipped through the water with less water resistance during a strike.
Moreover, the slenderness of the skull of Spinosaurus helped to create a comparatively small profile when it was seen head on. This gave the dinosaur the same advantages that I demonstrated plesiosaurs had by having a small head at the end of a long neck. It is also the reason why the fish-eating Ichthyosaurs had such long, thin snouts. With its huge body hidden behind its neck and narrow jaws, Spinosaurus was able to generate considerably less turbulence in the water as it crept toward its prey. The reduced pressure waves its muzzle generated would have been perceived by the lateral lines of schooling fish as just another member of the school, especially in muddy water or if approached from the rear. https://www.kronosrising.com/plesiosaur-necks-long-part-2-testing-theory/
Lastly, the pressure sensors (foramina) lining the skull of Spinosaurus would have enabled it to feel fish near it even in the dark. This has been demonstrated by alligators, which possess integumentary sensory organs (facial foramina), and can detect tiny disturbances in the water around them, even under pitch black conditions. Muddy water would have been no defense against Spino. Moreover, unlike other theropods like Tyrannosaurus or Carcharodontosaurus, which, according to my past research, evolved similar foramina on the lower portions of their jaws so that when drinking water they could detect the threat of approaching crocodylomorphs, Spinosaurus had sensors over a large portion of its head, enabling it to detect disturbances in the water even when fully submerged. https://www.kronosrising.com/tyrannosaurus-rex-was-not-sensitive-lover/
A comparison of the foramina in Spinosaurus vs Tyrannosaurus. (image credit: Wikimedia Commons)
Did Spinosaurus have any enemies?
Although, in the water, its size and toothy jaws made it largely immune from predation (the exception being if it ventured out to sea, where it would have risked attack from the largest of pliosauridae), Spinosaurus was most vulnerable on dry land. Its elongated 5.5-foot skull was fragile when compared to the flesh-rending jaws of its most feared contemporary, the “African T. rex”, Carcharodontosaurus.
Members of the genus Carcharodontosaurus were lethal hunters that preyed on dinosaurs. The larger of the two species, C. saharicus, had a skull 5.2 feet long and is estimated to have reached approx. 42’ in length with a weight of 8.6 tons (Molina-Perez et al 2016). That made it as large and powerful as Tyrannosaurus rex. There is little doubt in my mind that, when a Carcharodontosaurus encountered a Spinosaurus resting on the shore or laying its eggs, it was tempted to make a meal of it. And, unlike in JP3, Spino was simply not designed to slug it out with a towering predator that could take down sauropods.
As I’ve said before, gharials don’t battle crocodiles. In a Spinosaurus vs Carcharodontosaurus battle, if the latter managed to lock its jaws onto the comparatively fragile skull of Spinosaurus, it would cripple or kill it.
In a Spinosaurus vs Carcharodontosaurus matchup, how did Spinosaurus defend itself?
This is one of those rare instances when I get to introduce a personal theory of mine – one that, to the best of my knowledge, has never appeared in any scientific paper. Before I delve into it, however, I want to state this publicly; there have been several incidents thus far where paleontologists have published papers containing material that, put politely, appears to have been “heavily inspired” by blog posts and press releases of mine. One of these included my published theories on how plesiosaur necks evolved in relation to the lateral line of fish (https://www.kronosrising.com/plesiosaur-long-necks/). The offending parties in this matter have been notified, and I am hopeful that the situation will be resolved in an amiable manner.
That said, if any researchers are inspired by my Spino research, or anything else that I have worked on, kindly take the time to reach out and make sure that credit is given where credit is due. As a full-time novelist who dabbles in paleontology, it is difficult for me to continuously publish one formal scientific paper after another. My plesiosaur locomotion study (Hawthorne et al 2019) was a long time in coming. I will complete papers on all my theories, in time, but I am also content to be listed on a paper as a contributing party, should there be interest. Please do the right thing. Remember: paraphrasing plagiarism is still plagiarism.
With that out of the way, let’s return to our research. I believe that, with it possessing shorter hind legs than traditional theropods (Ibrahim et al 2020), a significantly smaller pelvis than other theropods (Wikipedia) and a center of gravity that was much further forward than in dinosaurs like T. rex, Spino was not able to walk around bipedally (Ibrahim 2014). I do, however, believe that it was capable of rearing up when it needed to, like a bear, for example, or a giant sloth, or a giant anteater.
The sloth makes for a worthwhile comparison, because large forms like Megatherium walked on all fours, with the weight distributed on the sides of their feet (hands included) because their claws prevented them from doing otherwise. It is the same with the anteater. Interestingly, Spinosaurus, like other theropods, could not pronate its hands, so the palms could not face the ground (Carpenter, 2002). However, putting weight on the sides of the hands was possible (Milner et al 2009). This means its forelimbs would have been utilized for locomotion in a manner similar to that of sloths and anteaters, and as a result the hand claws of spinosaurids would have not touched the ground and would have remained long and sharp.
This is important, because I believe that the front claws of Spino were what it used to fend off attacks from predators like Carcharodontosaurus.
Using talons for offense/defense is known throughout the animal kingdom. Although their use is not proven, it is likely that the thumb spikes of Iguanodon and the claws of Therizonosaurus were used defensively. Otherwise, they were practically defenseless. The same thing applied to giant ground sloths and to the extant giant anteater – they reared/rear up and used/use their sharp claws to defend themselves. Spino had large claws on its forelimbs, with an enlarged claw on the first digit. Interestingly, we see a similar development in the forelimbs of the spinosaurid Suchomimus, which had powerful forelimbs and a huge talon on each thumb. Despite being bipedal, it was also a piscivore and had a similar long, slender skull. That put it at risk for damaging attacks from larger, more powerful macropredatory theropods, just like Spinosaurus.
How did Spinosaurus use its claws defensively?
I believe that, when threatened by a theropod like Carcharodontosaurus, Spino’s first instinct would be to take to the water. This is just common sense. Why risk being wounded or killed when one can simply retreat?
If it was unable to do so, however, for reasons such as nest building/egg laying, traveling from one river or lake to another, or perhaps just getting caught basking in the sun, I believe Spino’s next tactic would be to bluff. It would rear up on its hind legs using its powerful tail like a tripod to give it stability (note: giant sloths and giant anteaters behaved/behave in a similar manner, with the tail used for support). It would use the S-curve in its neck to pull it back out of harm’s way, and probably put on a threat display – hissing, roaring, snapping its jaws, etc.
It is likely that, after being on the receiving end of one or more blows like that, the attacking theropod would retreat in favor of easier prey.
This footage of a giant anteater fending off an attack from South America’s dominant predator, the jaguar, gives a perfect example of how Spinosaurus may have defended itself in a Spinosaurus vs Carcharodontosaurus encounter. The anteater, with a slender, vulnerable snout, uses its tail for balance and lashes out at the big cat with its long, sharp claws. Scaled up mass-wise eighty times or so and once can imagine the kinds of confrontations that took place 100 million years ago.
In conclusion.
So, yes, it is confirmed: Spinosaurus was a largely aquatic dinosaur. Even “worse”, and yes, it was a bitter pill for diehard JP3 fans to swallow, it fed primarily on fish. Still, it was a beautifully designed predator, perfectly adapted to its watery domain, and to its prey. Spino’s skull was specialized. It was great for “reeling in the big ones”, but when forced into a Spinosaurus vs Carcharodontosaurus fight to the death, it was not so great at slugging it out with the bad guys.
However, it did have two things in its favor: a matched set of talons that I believe it used whenever it needed to defend itself. It was like a boxer with knives sticking out of their gloves. And let’s be realistic; if you’re going after a boxer and you’re like most theropods – meaning you’re using your face as a weapon – you’re going to get hit. The odds are, the world’s largest fisherman went extinct due to habitat changes instead of losses sustained from predator/prey interaction. Because, based on the preponderance of evidence, it appears it was quite capable of defending itself.
Thanks very much for stopping by, and I hope you enjoyed my theory on Spinosaurus and its defensive capabilities. I am excited to announce that my new novel, KRONOS RISING: KRAKEN (volume 3) is now on pre-sale and available for purchase. The release date is this July 4th, s check it out!
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Best,
Max
