T. rex vs. Spinosaurus: The Truth

Edit: Portions of this post’s text were updated 23 July, 2019.


It’s the prehistoric showdown that’s swept the world since Jurassic Park III in 2001 – rivaled only by the legendary conflicts of Tyrannosaurus vs. TriceratopsVelociraptor vs. Protoceratops, and Allosaurus vs. Stegosaurus.

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Immortalized by a one-minute fight, Tyrannosaurus vs. Spinosaurus was the first time two reasonably modern versions of predatory dinosaurs got violent on the silver screen. Initially with the upper-hand with its bone-crushing maw, T. rex was bested by the durability of its opponent. Using its dextrous front limbs, the Spinosaurus gripped the rex by the neck and snapped it – leaving the other dead on the ground.

It makes for a tense moment, sure, but as we’ve mentioned before – dinosaurs couldn’t pronate their hands like that. So, the MK-finishing move that the spino used was moot.

Let’s talk about the real Tyrannosaurus and the real Spinosaurus. Let’s do a breakdown of what makes each dinosaur tick as well as some of their defining characteristics. Ignoring the fact that they lived thousands of miles and millions of years apart, let’s beg the question: If they could ever meet, who would win in a fight?

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Going by alphabetical order, Spinosaurus is first. S. aegyptiacus, discovered in Egypt, was a semi-aquatic predatory theropod. I’ve restored it with plumage* that resembles the common loon (and the individual in question is named Becky, for those of you people who like to watch movies featuring anthropomorphic blue tangs). It’s an awfully big animal, and that seems to strike most people. Upper estimates of Spinosaurus‘ size go upwards of some twenty meters in length and over 7.25 tonnes (8 US tons). The animal pictured before you is a more conservative size estimate (somewhere in the neighborhood of 17-18 meters).

*(2019 addendum: this animal probably wouldn’t feature significant, if any, feather coverage)

Your Dinosaurs Are Wrong, while also functioning as one of my favorite YouTube series of all time, has done a segment on Spinosaurus that explains spinosaur locomotion. The center of gravity for this animal, were it to walk bipedally instead of doing its typical swimming, would’ve been too far forward. It would’ve fallen on its chest (a quite possibly fatal injury!). To compensate, the dinosaur would’ve needed to adopt a more tripodal stance with its neck reared back to provide proper balance. So, the animal probably wasn’t all that graceful on above water. Imagine a giant duck that kind of struggles to retain its balance, stumbling about from place to place as it did whatever it needed to on land.*

*(2019 addendum: new restorations of Spinosaurus show this animal as biomechanically competent in the “typical” theropod pose)

We can say, with confidence, that Spinosaurus was an at least semi-aquatic animal based on oxygen isotope analyses of it and several of its relatives. The hook-like talons on its hands were also perfect for swiping and scooping up aquatic prey. Consider it the prehistoric equivalent to a polar or grizzly bear.

Also, the raised vertebrae on the back was likely not a thinly-covered sail used for thermoregulation. It was more likely covered in a large “hump”* of soft tissue and used to make the animal look bigger or for intraspecies identification.

*(2019 addendum: it was more of a thinly-covered sail than a hump; whoops!)

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Tyrannosaurus rex, however, was very much a terrestrial predator built for high-shock, high-risk attacks on heavily armored prey such as Triceratops and Ankylosaurus. Size estimates of this dinosaur also vary, but never exceed 12-13 meters in length (weights are all over the place, but it’s safe to say that it was at least ~5.44 tonnes*). Stalking the environments of North America during the Upper Cretaceous, it probably saw the very end of the Mesozoic with the catastrophic K-T extinction event. Widespread and effective as it was, how did it manage to make it so far into the game?

*(2019 addendum: nope, let’s up that to 7-10 tonnes — also, T. rex’s potential for plumage is still up in the air as of July 2019)

We talk about T. rex‘s bite force here, a lot, but we should note that it could exert 8,273 Newtons-per-square-cm (12,000 PSI*). It could pretty much (withholding injury to the soft tissue in the mouth as a result) bite through cars, metal, and the like. Once again, this is a product of its environment and the available prey. The particularly skittish hadrosaurs of its time, though likely plentiful, were also easy pickings for competing predators. Going after the bigger, more dangerous game gave T. rex a slight edge in an untapped resource.

*(2019 addendum: it’s more along the lines of 8,000 PSI)

The growth series of Tyrannosaurus may also illustrate changes to its lifestyle as it matured.

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I recently visited the LACMNH in…well…Los Angeles. They have a rather impressive cast+fossil skeleton mount of three (they have four, but the other one’s in the main lobby) Tyrannosaurus of differing ages. Youthful T. rex – like the one in the center – had proportionally long legs. As they matured, their legs would actually get proportionally shorter until their growth peaked. What does this imply? Slimmer, lankier tyrannosaurs could’ve pursued faster, more agile prey than older ones. Where they lacked the muscle power and pure force to take down a Triceratops, young T. rex would’ve had ample prey in the form of quick Ornithomimus, juvenile Alamosaurus, and so on.

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And so, we have these two titanic raptorial theropods illustrated side-by-side. Let’s return to the question: Who would win in a fight?

The answer?

They wouldn’t.

Both Spinosaurus and Tyrannosaurus were very specialized predators whom have rule over different terrain and target different quarry. Most fights between predatory animals occur over resources, such as a recently-killed prey animal, territory, etc., and are often intraspecific. A T. rex is more likely to fight another T. rex for food, and so on. T. rex and Spinosaurus developed specializations that allowed them to live without worry of competing with any predators other than themselves, for the most part.

We’ll also consider Spinosaurus‘ environment for this conclusion. It lived in an area full to the brim with large predatory dinosaurs that rivaled T. rex in size. The high density of large carnivores in the same environment led to the local spinosaurs adopting an aquatic lifestyle, where food and space was abundant and unclaimed. In T.  rex‘s case, Utahraptor, Dakotaraptor, and young Tyrannosaurus took on fast and skittish quarry, leaving adult T. rex to seek other sources of meat – namely dangerous terrestrial herbivores.

In a scenario where an adult T. rex and an adult Spinosaurus could have crossed paths with one another, the chances of a fight breaking out would have been slim to none. Seeing two fearsome animals casually stride by each other is definitely a strange thought to stomach, but it makes sense.

There are more fish to catch and more Triceratops to behead, anyway. Who has time for a movie fight?

Until next time!

TL;DR – NeitherSpinosaurus and Tyrannosaurus evolved to fit different ecological niches, seeked different prey, and took up different resources. If they ever could meet (and they couldn’t, since they didn’t exist at the same time), there probably wouldn’t be a fight – since they’d have nothing to fight over!

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Dinosaurs & Pronation: An Observation

Typically, when kids (or adults acting like kids) pretend to be a dinosaur, they kind of hunch over and open their mouths wide and make guttural roars and slobber everywhere. Another thing they do is position their hands like this:

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And that’s your typical “rawr I’m a dinosaur” stance, right?

Of course I’m here to crush dreams and ruin childhoods – it’s part of the mission statement. Dinosaurs actually never held their hands this way. Ever. Never ever. Their wrists would’ve had to break in order to achieve such a pose (or flap their wings, but we’ll get to that later). The easiest way to look at this is if we observe your run-of-the-mill theropod.

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Placing your hands and feet in a pose that has your palms and soles facing the ground is called pronation. The stereotypical human emulation of a dinosaur features both pronated hands and feet. In dinosaurs that are emulating…well…themselves, only their feet are pronated. Their hands are non-pronated, meaning that they’re pretty much always ready to clap (tyrannosaurs and abelisaurs, with their tiny arms, are not part of the “able-bodied clapper” club).

The reason behind dinosaurs never evolving the ability to pronate their hands is unknown. With bipedal dinosaurs, it’s simply not necessary due to their preference to handle objects with their mouths and would use their hands to rake/slash. The really interesting thing, though, is that quadrupedal dinosaurs are also feature non-pronated hands!

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Let’s look at Scott Hartman’s Triceratops skeletal.

Dinosaurs walked in a digitigrade stance – meaning that they stood on their toes while a fleshy “sole” made of fat and other soft tissues made up the rest of the hand/foot for support (although it’s possible that some dinosaurs may have adopted a plantigrade stance – with their true soles against the ground – on occasion). This is true of the front and hind legs. We’ve established that dinosaur hind feet were naturally pronated, but what of the front?

Observing the Triceratops, we can see the arrangement of the fingers on the skeleton and my hastily-made top-down view of what the foot would look like if you cut through the leg. I’ve pointed out what would be the “palm” in animals with pronated hands, like humans, and notice how it’s still positioned to face the other hand and NOT the ground! Dinosaurs just didn’t have pronated hands, and evolution seemed to accomodate for this strange exclusion over their natural history.

That is, until the birds came along.

You should know by now, after a fairly long time of this being hammered down by paleontologists, that birds are dinosaurs – having split off from small theropods around the mid-Jurassic and possibly continued to branch off other ancestors through the remainder of the Mesozoic. You should also know, by just observation, that when birds fly, they hold out their wings – facing down.

One must wonder: “Wait. Charles. You just said that dinosaurs couldn’t pronate their hands!”

Yes. I know.

But look at how a bird flies. The only way the…”hands” pronate is with a fully-extended front limb to the sides. When a bird flaps, it then brings its arms inward and down, and the wings face one another once again. This movement of the entire arm to its maximum extension, laterally, is the only way that birds and some dinosaurs have been able to achieve pronation – not in the way that mainstream media and people imitating dinosaurs have depicted. More detail about musculature and wrist positioning is available, but I’m not a complete expert on such topics.

So – TL;DR

  • Dinosaurs can’t pronate their hands the way people think.
  • Quadrupedal dinosaurs still don’t have pronated hands – they walk on their toes.
  • The only way for dinosaurs to achieve a pronated hand posture is if they could stretch out their arms a sufficient distance to twist the wrist – and a limited amount had the musculature to do so.

Until next time!