After the success of The Lost World: Jurassic Park, the minds behind the franchise were in a bit of a fix. Tyrannosaurus and “Velociraptor”* had the run of the fictional islands for the past two movies; something new was needed to up the ante. The decision was made to make Spinosaurus the new villain in Jurassic Park III, the strange theropod being said to possess an 8-foot-long skull and stretch 60 feet from the tip of its crocodile-like snout to the end of its tail by the creative team. As if this weren’t enough, the writers of the film had Spinosaurus kick the tar of of Tyrannosaurus, trying to drive the point home that Spinosaurus was the biggest, baddest dinosaur that ever lived. But was it really?

* I put Velociraptor in quotes as the film version is really meant to be Deinonychus, although the mistake has never been corrected in the films. This messy attitude towards taxonomy can make things confusing for the public, especially when Jack Horner said in an interview that skulls of Velociraptor have only recently been discovered. This is blatantly false. While the skull of Deinonychus has undergone some changes based upon new discoveries of fragmentary material and recently discovered relatives, the complete skull of Velociraptor has been known since 1924.

With dinosaurs there is often a fascination with the biggest, the fiercest, and the weirdest, and for about 80 years Tyrannosaurus was the carnivorous dinosaur, the living terror of the Cretaceous. Around the turn of the 21st century, however, numerous reports appeared about theropods from Africa and South America that may have been ever bigger, but the question of what “bigger” means is a bit hazy. Are we talking about length? Height? Weight? As with the largest of the sauropod dinosaurs, which dinosaurs is the “biggest” may depend on what sort of information you choose, leading to a sort of “My dinosaur is bigger than yours” contest.

Lets start off with figuring out just how big Spinosaurus was and what evidence is available to figure this out. First described by the German paleontologist Ernst Stromer in 1915, the original material primarily consisting of part of the maxilla, a lower jaw, and a number of vertebrae bearing elongated neural spines, the dinosaur bearing a “sail” on its back. Unfortunately this material was destroyed in 1944 during an Allied bombing raid on Germany, although Spinosaurus lived on in many popular books, often portrayed as a kind of tall-spined Allosaurus.

In 1996, another Spinosaurus specimen turned up, the fossils leading paleontologist Dale Russell to erect a new species (Spinosaurus marocannus), although the 1996 material probably belongs to the species Spinosaurus aegyptiacus established by Stromer. The skull was estimated to be a little more than four and a half feet long, a little bit shorter than the estimate given for the original Spinosaurus material. In 2005, however, a new paper appeared in the Journal of Vertebrate Paleontology (Dal Sasso, et al 2005) describing a much more intact portion of the skull (containing the premaxillae, maxillae, nasals, and what appears to be part of a small crest), the size estimation for the skull of this specimen being about five and 3/4 feet in length.

What does this mean for the Spinosaurus in Jurassic Park III? The film appeared in theaters in 2001, requiring several years of preparation. The largest skull portion, the one described in 2005, was discovered in 1975 but was in a private collection until 2002, so it is doubtful that it provided the basis for the JP III dinosaur. Even if it did, the actual estimated skull length falls more than two feet short of the eight-foot measurement Jack Horner gives in an interview on the special features section of the DVD, and it seems as if the size of Spinosaurus was pumped up to make it seem even more impressive.

Even if the Hollywood version of Spinosaurus was super-sized, it was still among the largest of the theropod dinosaurs, its main competition being Tyrannosaurus, Giganotosaurus, and (although not typically mentioned, probably because it wasn’t a terrifying predator) Therizinosaurus. Determining which was the largest, however, has been a bit of a problem. Tyrannosaurus is known from a number of skeletons that have provided paleontologists with an excellent idea of what the whole animal looked like, even at various times during the life of the animal. With other theropods we aren’t so lucky, specimens being less numerous and more fragmentary (although this will hopefully be subject to change as the years roll on). A study published by Therrien and Henderson in 2007, however, suggests that skull length and body length in theropods is tightly correlated; as theropods become larger their skulls become proportionally longer compared to their body size.

The problem is that not all theropods were feeding in the same ways, and the construction of their skulls could vary. Spinosaurids, for example, probably had proportionally longer skull for their body size due to their fish-eating habits, and this must be taken into account. Indeed, estimating overall body size for these dinosaurs can be difficult when the back of the skull (the are containing the orbit and the various fenestra) are unknown. In spinosaurids the back of the skull may be flatter, taller, and longer, and the slight differences impacting estimates of overall body size. (Likewise, if the skull of Therizinosaurus was anything like that of its smaller relatives, it could throw a monkey wrench into size estimates as it would have a comparatively tiny skull for its body size and potentially break the correlation between skull length and body length.)

We’ll leave Therizinosaurus to the side, however, and concentrate on the big, bad killers like Tyrannosaurus, Giganotosaurus, Carcharodontosaurus, and Spinosaurus. Although claims as to the “biggest” will likely persist continue, all of these animals were approximately 42 feet long and may have weighed about 14 tons. Some were slightly longer and heavier than others (i.e. Giganotosaurus and Carcharodontosaurus may have been a little longer and heavier than Tyrannosaurus), but they could all be grouped in the same heavyweight size class. On several continents, then, predatory theropods independently arrived at about the same size, suggesting that they represent the “upper limit” of size and weight for primarily carnivorous, bipedal dinosaurs. Perhaps they could have become even larger if they became quadrupeds, but this would have required drastic changes to their morphology and behavior, and the variation to initiate such an evolutionary shift did not arise among predatory dinosaurs with big, heavy heads and small forelimbs (nor do I see much reason why it should).

Rather than quibbling over which theropod was the biggest, it’s important to recognize that there were several “ways” to be a large predatory dinosaur. Although all similar in size, Tyrannosaurus more than likely had very different feeding habits than Spinosaurus, and while Giganotosaurus may be closer to Tyrannosaurus in shape, it was dealing with a different group of prey animals than the North American “Tyrant King.” Still, the reasons why Spinosaurus appears to be so large is somewhat vexing. For Tyrannosaurus and Giganotosaurus, an evolutionary arms-race where predators and prey keep getting larger seems intuitive, but why would an animal that seems well-adapted to eat fish get to be so big?

I have little doubt that Spinosaurus was not a strict piscivore, but perhaps its size has something to do with partitioning of prey resources and competition with abelisauroids and carcharodontosaurids, the three types of theropods often found in close association to one another in Africa and possibly elsewhere. The real answer still awaits further analysis, but the varying impacts of convergence and contingency in these large predatory dinosaurs is exceedingly fascinating.


Dal Sasso, C.; Maganuco, S.; Buffetaut, E.; Mendez, M.A. (2005) “New Information on the Skull of the Enigmatic Theropod Spinosaurus, With Remarks on its Size and Affinities.” Journal of Vertebrate Paleontology, Vol. 25 (4),pp. 888-896

Therrien, F.; Henderson, D.M. (2007) “My Theropod is Bigger Than Yours … Or Not: Estimating Body Size From Skull Length in Theropods.” Journal of Vertebrate Paleontology, Vol. 27 (1), pp. 108-115


  1. #1 Brett Booth
    April 27, 2008

    After seeing the restoration of the new Russel mandible along with the Stromer lower jaw I’m not convinced they are from the same beast. The lower jaw looks to be from a much more robust animal. If I’m wrong, Spinosaurus was one ugly theropod that looks a bit like a pterosaur.

    I’m glad someone also thinks the size estimates of Spinosaurus are over exaggerated.



  2. #2 Wendy
    April 27, 2008

    I’ve never forgiven the makers of “Jurassic Park III” for the death of T. rex at the hands of stupid, ugly Spinosaurus. To this day, whenever we play with my son’s collection of plastic dinosaur “action figures,” I always make sure that Spinosaurus loses – and badly – in any battle with T. rex. Oh yeah. Spinosaurus gets STOMPED in our house. ­čśÇ

  3. #3 Blake Stacey
    April 27, 2008

    Maybe the genetic engineers mixed up the test tubes. . . or perhaps Spinosaurus underwent a rapid form of island gigantism on Isla Sorna. . . .

  4. #4 Lee Drake
    April 28, 2008

    I’m curious if anyone’s done a survey of the various candidates for “biggest predator”, including rarer taxa such as Saurophaganax and others.

    I like you’re point on how feeding methods are the best way to make giant predators unique, but do we know enough about the fauna to begin to approach that question? Shed teeth aside (which have equifinality issues due to scavenging), it seems that while a good point, it is ultimately untestable to a satisfactory level.

  5. #5 Sordes
    April 28, 2008

    I also thought for a long time why spinosaurus grew so huge. Perhaps because a diet which is based on big fish is actually a good start. I find it interesting that among all living carnivores, the bears are without any doubt the largest ones, surpassing the largest tigers and lions with ease. But neither kodiak bears or grizzlies are really fierce hunters (at least compared with big cats), or would be even comparable poor hunters, if they had to prey on ungulates or similar prey (although they sometimes do it and not always that bad). I could even imagine that if we could only know the fossils of bears a lot of paleontologists would attest that many bears were scavengers which were too slow to hunt and used they size to…well, you know it.
    But despite being comparable poor hunters, the bears that come closest to spinosaurids by catching a lot of prey with their claws are extremely large, and that is a good indication, that a mainly piscivorous (okay, seals are no fish, but the way they are caught is not that different from salmons caught by brown bears) diet is probably more efficient for a large hunters, than it seems. They don┤t have to be fast, and it is no problem for them to store a lot of fat. As long as they get enough food, they could grow and grow.

  6. #6 johannes
    April 28, 2008

    > but why would an animal that seems well-adapted to eat fish get
    > to be so big?

    A shadow will attract fish, so perhaps a large shadow caused by huge size and a sail on the back will attract even more fish?

    And fishing is a rather stationary occupation, running speed doesn’t matter much, so there are fewer weight limitations than on a terrestrial predator that has to run after its prey. The only limitation on size and weight is the size of the available prey, and its numbers.

    Large size is also a good defence against crocs.

  7. #7 David Marjanovi?
    April 28, 2008

    You didn’t mention that the bombed vertebrae are from a subadult: the neural arches were still not fused to the centra. Immense as that beast was, it still had quite a bit of growing to do!

    Spinosaurus marocannus

    S. maroccanus.

    why would an animal that seems well-adapted to eat fish get to be so big?

    Perhaps because the lungfish Neoceratodus africanus was incredibly big, too…

    Large size is also a good defence against crocs.

    This, of course, holds doubly in the presence of Supercroc (Sarcosuchus imperator).

  8. #8 Zach Miller
    April 29, 2008

    First off, I’d like to submit my own thoughts on the subject of spinosaurs. I have thought more on the subject since, and I wonder if spinosaurs developed osteosclerosis? I also wonder if spinosaurs and Sarcosuchus operated in different waterways. Given its enormous size and obvious aquatic habits, one would assume that the giant croc lived in large rivers or giant lakes. I doubt that spinosaurs would have been able to compete directly for giant lungfish with Sarcosuchus, so perhaps they hunted their slippery prey in streams and creeks?

    I suppose I’d like to know what, exactly, the environment was like for Baryonyx tenerensis, Spinosaurus, and Suchomimus. Oh, and Irritator, because it lived in a different place than either of the other two spinosaurs.

  9. #9 Mike Keesey
    May 1, 2008

    why would an animal that seems well-adapted to eat fish get to be so big?

    Competition with certain other piscivorous archosaurs?

  10. #10 Todd Hemming
    February 23, 2009

    I suspect Spino got so big because of the huge fish which may have been available to it. Probably huge 9ft scaly fish which were known to have occupied many of the inland waterways.
    With Croc power jaws (but reletively more massive)and massive strong arms, it should not be underrated in any way.The arms could have lugged out huge 1 ton fish with ease and ripped them apart (the pressumed use for the huge sharp claws)
    Rex would certainly be matched, without any grappling arm ability, being a major disadvantage.
    Todd PhD P

  11. #11 Raymond Minton
    February 23, 2009

    As a dinophile, I watched the “Jurassic Park” series avidly, but was very frustrated by the fact that, even though paleontologists were hired as consultants, the film makers played fast and loose with the facts for “dramatic” purposes. They really got carried away with the Spinosaurus. No matter which one of the theropods was biggest in absolute terms, T-rex will always be the tyrant king to me, and he’s still clearly superior to some of these pretenders in important ways, among them better eyesight, more powerful jaws, and a bigger brain. So there!

  12. #12 caleb
    May 17, 2010

    spiosaurus was the biggest man!

  13. #13 normandy
    May 5, 2011

    i dont care

  14. #14 prefabrik
    May 12, 2011

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  15. #15 rehau
    May 17, 2011

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  16. and the interactions of males with infants, so altogether these observations could be used to quantify the details of social relationships between females and their male friends.

  17. #17 Curtis
    September 9, 2011

    yes the spino is big, yes its prey is big and varies, i doubt that a beast of the size of a spino eats just fish. BUT in nature’s grand plan it make one wonder what hunted the spino. any and ever animal on this plant has a predator!

  18. #18 science
    November 5, 2011

    new news of a trex skull 40 feet tall(not the imperiator),trex was a hunter they proved it and giganotosaurus didnt even exist spino was only 14 feet at the top of the sail and was a crocodile and charcharos teeth were actually stolen sharks teeth so it ate plants and all other predators besides trex were scaventures and were 20 feet smaller than trex

  19. #19 science
    November 5, 2011

    also when trex appeard all other meat eating dinos whent exinct why? because trex killed them all!

  20. #20 Factz
    November 10, 2011

    Your pathetic^ You obviously grew up loving T.rex and is making up a bunch of lies to make it seem like the Chuck Norris of the dinosaur world.None of what you just said was true.The author is clearly just making a scientific observation of spinosaurus and low and behold…another argument on who was bigger appears in the comments. Everybody these days are so touchy about the large carnivores..especially T.rex.

    Just give it a break and stop acting immature. Anyways, I always questioned why spinosaurus grew so large myself. Maybe it was that food was so easy and plentiful? If it ate meat also it could It’s natural for animals to get larger and larger when more food is around.

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  31. #31 Johnny Minaya
    March 20, 2012

    I like your comment but you have to remeber Spinosaurus huge claws. Maybe his mouth is for fish and his claws were for hunting bigger prey. Maybe just like raptors instead of using thier heads they use very dangrous claws to basically rip thier prey to shred and then eat. Maybe spino did the same he used his claws to make his prey bleed to death. Maybe he would use his huge size to intimidate the animal then if that did not work he would moch charge to get a certain prey. Then run towards it then give it 1 or more slashs with those huge claws or it might of runed down the creature becasue in my studies as a 13 yr old boy I have learned in a show called Monsters Ressurected that Spinosaurus was actually fast compared to it weight. Also it probably didnt have to worry about other predators. It could of done such a Therizinosaurus did flash its claws before attack. But if that did not work it couls turn side ways and show it spine and if it had blood vesels in it, it would flush blood in it to make it look more frighting snd bigger

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