Spinosaurus bite force

[Grey]

A famous discussion.

Spinosaurus, because of its sheer (still not determined) size and its near mythical status based on the lack of complete remains, is one near-mythical extinct genera to now, even more since his appearance facing a Tyrannosaurus in the last Jurassic Park movie.

To determine the true predatory power of the actual animal, many attempts have been performed by enthusiasts to predict the potential bite force of Spinosaurus.

As I was a long time defender (perhaps somewhat biased) of Spinosaurus performing a decent bite force in absolute standards, I tend to change my opinion about it.

One hint from Manabu Sakamoto, who had precited the bite force of a 8 m Baryonyx.

In order to estimate bite force with any reasonable confidence, we'd need to have a rough idea of how much jaw muscles Spinosaurus had. Unfortunately there are no good cranial materials to reconstruct jaw muscles in Spinosaurus - the bits at the back of the skull where the muscles would have attached are not known for Spinosaurus. Therefore we won't know for sure.

However, we can fairly confidently assume that Spinosaurus would have similar skull proportions to those of close relatives like Baryonyx or Irritator. These theropods had long narrow skulls with not much space for jaw muscles. From what we know of Spinosaurus skull materials, we can be sure that it also had smallish jaw muscles (for an animal of that size).

Extrapolating from size estimates (I presume body size, e.g. body mass, body length, whatever) would not give you a good estimate for Spinosaurus, for the very reasons I outlined above, i.e., spinosaurs had smaller jaw muscles compared to other theropods of similar sizes. Using body size will grossly overestimate bite force.

www.askabiologist.org.uk/answers/viewtopic.php?id=9468

I think Sakamoto posted others messages on the source where he stated with absolute certainity the relative weak bite force of spinosaurs.

So far, I don't trust anymore the enthusiasts predictions, often taken as a freaking fact, of Spinosaurus exerting a bite force of 2-3 tons.

[creature386]

Mar 1, 2013 2:39:44 GMT 5 Grey said:

So far, I don't trust anymore the enthusiasts predictions, often taken as a freaking fact, of Spinosaurus exerting a bite force of 2-3 tons.

I agree.
I also have to say that I get sick when people are ridiculing people who think that Spinosaurus had a weak bite.
Just for saying that, I don't think Spinosaurus had a weak bite, but I have seen that people who think it got attacked and that is never a good idea, especially when their point is not a solid fact.
Of course there is also the other way around, people ridicule other people if they think that Spinosaurus did have a strong bite, but that's another story.
There are generally lot's of rude debates regarding that subject, on both sides.

About the bite force in Spinosaurids, I would say this is relevant:
whenpigsfly-returns.blogspot.de/2008/01/feeding-adaptations-and-strategies-of.html
It aswell includes interessting information about their nishes.

[Deleted]

This is relevant

translate.google.com/translate?u=http%3A//theropoda.blogspot.co.uk/2009/01/spinosaurid-paleobiology-more-than-just.html&hl=en&langpair=it|en&tbb=1&ie=UTF-8

"The skull shows no adaptations to shake prey violently, the bite and teeth probably did the killing. The cranial and mandibular muscles therefore suggests that Spinosaurus evolved an "impalement" mechanism for medium-sized prey, grabbing with a bite that is relatively fast and powerful" - Andrea Cau

I only fixed the grammar.

[Dakotaraptor]

I think some people from CF think the Spinosaurus bite was around 3 tonnes because of someone that made estimate based on 18 m "goliath".

Anyway more than 1.5 ton bite force is not 100 % impossible.

[theropod]

3t is probably overestimated because of the size estimate that was used. Best would be to scale by skull size, which is a factor we can determine relatively well.

I am not agreed with 2-3t being ridiculous. We have to put things into perspective. What Sakamoto wrote is absolutely true, for its size its bite was certainly rather weak. Probably weaker than other theropods even in absolute terms. But that doesn't mean it has to be MUCH weaker. I may recall when based on Allosaurus (Bates & Falkingham, 2012) Carcharodontosaurus would already have an adductor force of more than 3t, the same can probably be said for most giant theropods, with the exception of T. rex which likely even topped 6t.
We cannot rebutt it at the moment, just speak in probabilities. It is probable that going by tooth design, purpose, bite force estimates and jaw size the bite force of Spinosaurus was reasonably strong in absolute terms.
2t for a MNSN V4047-sized Spinosaurus sound good for me.

Taking anything as factual is premature, so is excluding hypotheses based on such the limited data.

Rebutting fanboys/haters who think Spinosaurus had a bite force of mere 500kg or so (!) is pretty save tough, that figure is just plain ridiculous.

[creature386]

Who said 2-3 t is ridiculous? Grey only said it isn't a fact. Anyway, I too see 2 t as likely.

[Dakotaraptor]

Probably haters.

[Fragillimus335]

2-3 tons IS pretty weak for a 12 ton theropod. If it were as "tough" as Tyrannosaurus in the biting department one would expect a bite force of around 9-10 metric tons!!!

[creature386]

You have to remember that it did not just have a thinner, but also a proportionally much smaller skull than Tyrannosaurus.

P.S. How did you get the 9-10 t number? You know that bite force does not rise linearly with mass? Smaller animals have much stronger bite force lb for lb than larger ones.

[theropod]

When scaling by mass, one has to use (M/m)^2/3*f=F (which basically takes the cuberoot of the weight difference and then the square of that)
When scaling by (skull-) lenght you can just use the square instead of the cube.

[creature386]

So, if it's bite was as tough as the one of Tyrannosaurus, it would have a bite force of 7-8 t?

[theropod]

If it was an upscaled T. rex, or built for powerful biting just as much, yes. It obviously isn't, but this could give an idea just how much weaker than usual the 2-3t range would already be. An upscaled Carcharodontosaurus would also have a bite force of at least 4t.
So those figures may sound exagerated considering the usual hater claims of 500-1000lb, but if we put it into perspective it is very low compared to other theropods when normalised for size.

I'll repost what TheROC wrote on Carnivora:

Let me reiterate.

Dr. Manabu Sakamoto back on the dinobase forums around 2009, told me about some unpublished bite force estimates for Baryonyx, here. He said 3800 N (854.3 lbs of force). He said the skull he worked with was based on the Baryonyx specimen in the Natural History Museum (NHM) in London. Dr. Sakamoto agreed that it was probably 28 feet long. And from there I just scaled up to a possible 18 meter Baryonyx specimen, keeping in mind that muscular strength (jaw muscles are included in that of course) goes up as a square of the scaling factor, and came to the conclusion that a 18 meter baryonyx would have about a ~2 ton bite.

From there, just came a bit of guess work for an 18 meter spinosaurus, I reasoned that its mandible is significantly deeper than Baryonx's proportionately, that it might yield a bite force 50% greater than a baryonx skull of equal size. Which is where the ~3 ton bite force guess originally came from, as that's 50% greater than 2 tons. I feel a 50% stronger bite force at equal skull lengths is reasonable, considering the often great differences we see in different dog breed bite forces, even when skull length is comparable between breeds.

The whole thing is of course, assuming spinosaurus has a skull as proportionately long compared to its body size as baryonyx does, which I believe is fair; dal sasso and crew did estimate the spinosaurus maxilla they worked with in 2005 to be 17-18 meters using the smaller relatives like baryonx to scale from. And afterall, large theropods tend to have proportionately larger skulls than their smaller relatives as a rule, which means I could be underestimating the bite force in actuality.

The baryonyx bite force is unpublished officially, yes, but I spoke with Dr. Sakamoto again in 2010 via e-mail and asked him about the exact same baryonyx bite force figure and he said he is still preparing the theropod bite force estimates that the baryonyx figure comes from, for publication--but that he had other things that took priority at the moment. --So it seems to me that the bite force figure is still viable to discuss, at least within our circles(since we can't add it to wikipedia yet since its still unpublished).

Also, within that e-mail I discussed with him the study that you seem to be referencing in your opening, Grey. It is in fact Dr. Sakamoto's study as well, and that was initially the reason I e-mailed him to inquire further about the study, (while asking about the unpublished baronyx bite force figures as an aside). He was kind enough to actually give me the full pdf of it over e-mail. The study is not about bite forces directly, but rather mechanical advantages of skulls. It shows mechanical advantages for dozens of taxa across their whole tooth row. The mechanical advantage of course becomes lesser the further you move away from the 'inlever' (which are the jaw muscles in this case), so that means the closer you are to the jaw muscles, the greater the mechanical advantage (which is obvious to everyone here of course, the back is where you bite hardest). He actually revised the Spinosaurus mechanical advantage stats using a different skull reconstruction later, here here and got higher values. Anyway, if we compare the mechanical advantage of say T.Rex and Spinosaurus, in the back of their tooth row, closest to their jaw muscles, they are actually quite comparable. Spinosaurus mechanical advantage at the back teeth was just about 0.25, whereas T.Rex was at about 0.28. At the front of the skull though, there is a bigger difference. Spinosaurus' mechanical advantage at the front of the tooth row is a little over 0.11, whereas T.Rex's is about 0.16. There are plenty of theropods with greater mechanic advantage values at the back of the tooth row than T.Rex however, Carcharodontosaurus for one, if just looking at equal sized theropods, has a mechanical advantage value of about 0.37 at the back of the tooth row.


Anyway, I feel Spinosaurus had to have a pretty hefty bite in absolute terms.

www.youtube.com/watch?v=MUQjslyarGI
See this Alligator Gar? Being chopped by an axe? Notice how difficult it is to do so, also notice how in one part of the video there are visible sparks made from the axe slashing along the scales? A lot of the types of fish Spinosaurus would have preyed on would have had the same kind of enamel hard ganoid scales, only they would have been even thicker ganoid scales since they belonged to bigger fish. Ganoid scales as you see, are quite hard, Native Americans even made arrow heads out of ganoid scales apparently.

Let's roll this up again, this time with the more reliable skull lenght (which should be more closely correlated with jaw musculature than total lenght)

Assuming a 1,8m skull for MNSN V4047, and a 0.91-1m skull for the Baryonyx holotype (latter is from NHM skeleton/Hartman's skeletal, former by my own reconstruction as well as Hartman's):

1,8²*380=1 231kg of force
(1.8/0.91)²*380=1 487kg

I think we can take this as the lower bound for now. No more claims of that ridiculous <500kg force. Since the mandible in Spinosaurus is deeper, as already explained in the quote, the teeth larger and more robust and the rostrum broader, it is probable Spinosaurus bit harder than that, how much I cannot say but imo 2t is reasonable.
Considering the mechanical advantage is probably similar to T. rex (which faciliates guesstimates), this fits the presumable muscle-sizes quite well imo.

Unfortunately the link doesn't work any more, so what we'll have to look up is what position in the mouth the force estimate was for.

PS: another off-topic observation that has been mentioned elsewhere; Carcharodontosuarus appears to have had quite a massive mechanical advantage. So even tough the muscles certainly where not as expanded as in some tyrannosaurines, that is of limited importance for its actual bite force, which may have been fairly strong (which in turn is relevant to the statements Sakamoto made about Spinosaurus´ bite force since they were in relation to these other theropods).

[coherentsheaf]

Jul 6, 2013 16:36:40 GMT 5 theropod said:

PS: another off-topic observation that has been mentioned elsewhere; Carcharodontosuarus appears to have had quite a massive mechanical advantage. So even tough the muscles certainly where not that expanded, that is of limited importance for its actual bite force.

interesting. This would imply that Carcharodontosaurus would only be able to produce high forces through a narrow range of motion, indicating that the assertion that T.rex had a smaller functional gape is wrong.

[theropod]

Isn't this about the leverage at tooth positions? The mandible or quadrate aren´t even known to deduce anything about the flexibility of the jaw joint...
It appears there can be a few more factors here.
Broader muscle insertions also limit gape, but shifting the toothrow backwards does not. By the use of the term mechanical advantage can apparently have a pretty broad range of possible meanings.

Allosaurus articuloquadratian gape is said to be over 90° (at least this is shown in Bakker, 1998). I'm quite sure Tyrannosaurids have lower ones (since several gape-enhancing specialisatons are observed and described in allosaurus while none of these are known in T.), despite Allosaurus having the higher mechanical advantage.
I don't know about Carcharodontosaurus, but Allosaurus has a high mechanical advantage (Bates & Falkingham, 2012), probably simply owing to its comparatively short jaws and a toothrow reaching pretty far back. Big forces don´t have to be transmitted in its bite, especially not by the jaw adductors and at a high gape angle. It is sufficient to drive the teeth into whatever it´s biting mainly with postcranial force, so "functional gape" isn´t always the same.

[coherentsheaf]

Jul 6, 2013 18:06:49 GMT 5 theropod said:

Really? How?
Isn't this about the leverage at tooth positions? The mandible isn't even known...
Broader muscle insertions also limit gape.

Allosaurus gape is said to be around 100° (at least bakker is reported to have shown that as a wikimedia reference). I'm quite sure T. rex has a lower one. I don't know about Carcharodontosaurus, but Allosaurus too has a pretty high mechanical advantage too (Bates & Falkingham, 2012).

High mechanical advantage means less flexibility at equal muscle mass. Even if these animals have large gapes we would expect them to employ large forces only through a narrow range if their muscle mass is much lower than that of Tyrannosaurus.