Highest bites forces in the animal kingdom

[theropod]

Yes, of course it is. That’s an elementary geometric law.

[Grey]

Well something that Hawthorne didn't get as well, his 100 tons Kronosaurus bites with a 50 tons bite force...

[theropod]

Keeping in mind comparable bite forces for Crocodylus and Pliosaurs at similar skull length:

Crocodylus niloticus (Britt et al. 2012, based on measurement method B)
Dorsal cranial length: 0.69m
Total length: 6.1m
Body mass: 1075kg

Kronosaurus queenslandicus (McHenry 2009, based on CRM 1)
Dorsal cranial length: 2.29m
Total length: 10.67m
Body mass: 11366kg

Total length in the pliosaur is 4.66 times the length of the skull, compared to 8.84 times in the crocodile. Body mass in the pliosaur is also almost twice higher at a given total length (9.36*tl^3 vs 4.74), yet at a given skull length, the crocodile is considerably more massive (3272*dcl^3 vs 946*dcl^3, the croc scaled to 10.667m would be 39.3t). So it’s the pliosaur that bites harder at the same body mass, simply due to its proportionately far bigger skull.

EDIT: Actually he is in the right ballpark. 100t is about 17 times as massive as the Kronosaurus for which McHenry made his bite force estimate, which would translate to being ~7 times as powerful if its bite force were to scale isometrically (of course a somewhat risky assumption over that kind of size range, but one that others have previously made in peer-reviewed works). If you assume this estimate for Kronosaurus being underestimated 2- to 3-fold, you get a range of figures for a 100t version that overlaps those 50t.

[Grey]

Aug 28, 2015 3:23:47 GMT 5 theropod said:

EDIT: Actually he is in the right ballpark. 100t is about 17 times as massive as the Kronosaurus for which McHenry made his bite force estimate, which would translate to being ~7 times as powerful if its bite force were to scale isometrically (of course a somewhat risky assumption over that kind of size range, but one that others have previously made in peer-reviewed works). If you assume this estimate for Kronosaurus being underestimated 2- to 3-fold, you get a range of figures for a 100t version that overlaps those 50t.

But we were discussing the geometric implication that the larger beast bites less harder than the smaller one. Using this isometric scaling is prone to overestimate (and I don't think he thinks about peak bite force in his statement).

[theropod]

I think you didn’t understand me correctly. That larger animals have proportionately weaker bites is the implication of isometric scaling.

That’s why a 100t pliosaur wouldn’t bite 17 times as hard at a 6t one, but just 7 times. Area scales to the 2nd power of length, mass to the 3rd, so the difference in terms of bite force is the difference in terms of mass ^⅔.

McHenry estimated QM F10113’s bite force at 27716N at a body mass of 5781kg (49% of body mass) and a dorsal skull length of 185cm. 100t is 17.3 times as massive, implying 6.69 as strong, implying an uncorrected 185380N or 18.9t (18.9% of body mass). If you multiply that by 2 and 3 that gives you 37.8t and 56.7t respectively.

[Grey]

But the question is, in the light of Foffa explanations, if the 2-3 times stronger assumption is correct or if it is only/mainly due to peak bite force.

[theropod]

Yes, that is the question. Not the (non-)question we discussed before though.

Peak bite forces were not just 2-3 times higher than MDB and dry skull estimates, look at table 3 in Foffa et al..

coherentsheaf: Could you reiterate regarding the basis of those "2-3 times"?

[theropod]

I got to talk to Davide Foffa at SVPCA. It's not simply due to the in vivo data being peak bite forces, it's due to fibre angle and the pterygoideus volume being underestimated by the modeling. He said mechanical advantage may be a better measure for comparative purposes.

It's pretty much impossible to tell something for sure, but I think the best indication we get is that pliosaurs and crocodiles end up similar at similar skull lengths.

[Grey]

Foffa previously told me that.

It's true that the supratemporal fenestra in pliosaurids is comparatively much larger than in crocs. But that's not the only factor. As you said the MUSCLE volumes are hard to understand because some muscles groups exceeds the bone boundary (muscle pterygoideus in crocodiles - and we simply don't know this about pliosaurs). Other factors are the muscle lines of action which influence the efficiency of the biting.

[theropod]

I know, you already posted that. That seems to relate to Forrest's suggestion that pliosaurs were proportionately stronger biters due to the size of their STFs.

Reality is more complicated than that.

[blaze]

Could the size of the supratemporal fenestra in pliosaurs be because of some other cause rather than biteforce? marine crocodiles convergently evolved huge supratemporal fenestra as did mosasaurs.

[coherentsheaf]

Aug 28, 2015 5:04:42 GMT 5 theropod said:

Yes, that is the question. Not the (non-)question we discussed before though.

Peak bite forces were not just 2-3 times higher than MDB and dry skull estimates, look at table 3 in Foffa et al..

coherentsheaf: Could you reiterate regarding the basis of those "2-3 times"?

I was going from McHenry's thesis. Ursus arctos also posted similar results regarding large mammal carnivores.

[Grey]

Someone would like to propose a top of the highest bite forces in fossil taxa using presumed peak/in vivo/max bite forces predicted from the published results ? For example, the maximum in :

a 13 m hypothesized "P. macromerus"
a 11 m Kronosaurus
a 15 m hypothesized "Liopleurodon" (based on the NHM symphysis) using P. kevani's data as basis
a maximum sized Purussaurus
a maximum sized Deinosuchus
the FMNH PR2081 Tyrannosaurus
a 18 m Carcharocles (using published data about body mass regression)
the MUCPv-95 Giganotosaurus
a 16 m Basilosaurus

[blaze]

Sept 5, 2015 5:45:10 GMT 5 blaze said:

Could the size of the supratemporal fenestra in pliosaurs be because of some other cause rather than biteforce? marine crocodiles convergently evolved huge supratemporal fenestra as did mosasaurs.

Before writing that I had found a publication explaining why marine crocs had huge supratemporal fenestra, I didn't mention it at the time because I only posted the above quickly before going to bed, next is my summary of Pierce et al. (2009) explanation, but first some abbreviations.

MAMEP: M. abductor mandibulae externus profundus
MPT: M. pterygoideus

In living crocodilians there's a relationship between the size of the supratemporal fenestrae and the adducture musculature (Endo et al. 2002). It has been shown that the size of the MAMEP and the supratemporal fenestrae are inversely correlated with the size of MPT and the pterygoid bone (Gadow, 1901; Iordansky, 1964). This means that long-snouted crocodilians have more strongly developed MAMEP and larger supratemporal fenestrae but reduced MPT and pterygoid bone while the inverse is true for short-snouted forms, this is explained by the roles of the two muscles, MAMEP produces rapid but weak movement due to its line of action being closer to the jaw joint while MPT being more distant, has large mechanical advantage and produces strong but slower movement.

How this relates to thalattosuchians? well, they all have small pterygoid bones and their secondary palate is not fully formed, limiting the area for muscle attachment for MPT, this imposes a severe limitation on the strength of their bites but they, specially the macrophaous taxa, overcame it by further increasing overall muscle mass, oversized supratemporal fenestrae means oversized MAMEP and such oversized muscles brute-force their way into having strong bites despite their low mechanical advantage, the tradeoff is that their skulls are structurally weaker due to the reduced skeletal mass at the back of the skull.

Now my own thoughts, given the similar skull design of thalattosuchians and pliosaurs I suppose they had similar limitations and converged in the same solution.