Spinosaurs Were Lousy Croc Mimics: They were Better!

[Fragillimus335]

phenomena.nationalgeographic.com/2013/05/30/spinosaurs-were-lousy-croc-mimics/

After running the virtual snouts through their biting paces, Cuff and Rayfield found that the upper jaws of the spinosaurs “absolutely outperform all crocodilian taxa” and showed similar resistance to bending and twisting to each other. As far as the front part of the upper jaw is concerned, at least, the spinosaurs were not just like big gharials. The spinosaur jaws were better at dealing with up-and-down stresses than side-to-side stress, as well, which is consistent with their relatively narrow jaws. And the apparent superiority of the spinosaurs seems to have been a result of their size. Rather than being a case of convergent evolution with slender-snouted crocs because of a fish-based diet, spinosaurs might have been able to get away with having relatively narrow jaws thanks to mechanical advantages conferred by size. They weren’t bonecrushers like Tyrannosaurus – not even close – but the spinosaurs had jaws that were capable of doing more than holding onto slippery fish.

[Fragillimus335]

New study shows Spinosaurs were not restricted to small prey!

[creature386]

What do you think would be a possible prey size range?

[theropod]

What's the title of the paper? found it. Seems many former studies' promises are coming true this year, we already had the same with Allosaurus. The last Rayfield study I read on this found the jaw of Spinosaurus to be relatively weak, but that was just a 2D fea and stated to require confirmation.

But I think this belongs on the feeding-apparata-thread, doesn't it?

[Grey]

Interesting but nothing looking like a revolution, we already suspected this.

The tests are interesting but I note that Baryonyx seems to have a more robust and resilient skull structure than the giant Spinosaurus.

Also, I read the Spinosaurus skull at 117,6 cm

By the way fragillimus, the title thread is a bit fanboyish...

[Fragillimus335]

Jun 2, 2013 9:07:50 GMT 5 Grey said:

Interesting but nothing looking like a revolution, we already suspected this.

The tests are interesting but I note that Baryonyx seems to have a more robust and resilient skull structure than the giant Spinosaurus.

Also, I read the Spinosaurus skull at 117,6 cm

By the way fragillimus, the title thread is a bit fanboyish...

It's basically the conclusion of the study!

[Grey]

I don't think that's exactly what the Bristol's guys had in mind at the end !

[theropod]

The used Spinosaurus was not Dal Sasso's specimen, but some other rostrum. No idea why they used it, Dal Sasso's isn't only more complete and larger but seemingly also more robust.

No, to be exact that was definitely not the conclusion of the study, this was:

It appears that the spinosaur theropod dinosaurs studied here achieved superiority in resistance to bending and torsion over representative crocodilians by nature of their large size. When size is corrected for, Spinosaurus performs relatively poorly compared to the other taxa. In comparison, B. walkeri performs surprisingly well, its oreinirostral morphology conferring greater resistance to dorsoventral bending and torsion than Spinosaurus and the gharial, to which B. walkeri has been compared in the past. Whether influenced by hydrodynamic or feeding related constraints, a combination of both, or other factors, the size-corrected alligator rostrum is well-equipped to deal with mediolateral and torsional loads, compared to our other study taxa. Our results only consider the portion of the skull anterior to the external naris, and a consideration of a larger portion of the rostrum is desired before a more complete understanding of rostral function can be obtained.

In conclusion, the unusual rostral morphology of spinosaurs conferred some advantage in dorsoventral bending resistance, particularly in B. walkeri, yet both species studied here were poorly equipped to resist mediolateral and torsional loads. Spinosaurus represents one of the biggest, if not the biggest theropod dinosaur [58], yet scaled to the size of an alligator, gharial or slender-snouted crocodilian, it performs poorly, especially in resistance to torsion. For a taxon such as Spinosaurus, the ability to feed on larger, struggling prey was not conferred by the possession of a snout that was relatively well equipped to deal with associated feeding loads, but may have been achieved by simple size-related advantages.

Baryonychines being more resistant is in accordance with Rayfield., 2011. Back then she also noted it was typical for larger taxa to have weaker skulls.

It is a bit annoying all these studies are always closing with the note they they are basically just arbitrary...

[Fragillimus335]

Well, that is obvious. If you scaled an alligator skull to 6 feet long it would out bite pretty much everything we know about, including rex. But I meant that the many people claiming Spinosaurus to have a weaker skull and bite than a modern 15 foot crocodile are very likely wrong.

[Grey]

Yes theropod, that's why I expressed some doubts about the claims of gigantics bite forces predicted in the giants extinct predators bite forces. Not that I don't believe in these (I use them) but that I always keep in mind the suggestion by Chuck Ciampaglio "As an animal becomes larger, much more of the animal's weight is consumed by support structures, not muscles".

[theropod]

As an animal gets larger, it also needs more muscle mass. Musculature is just as necessary as skeletal structures or ligaments, and can as well be regarded as a support structure in this context.

Think about it. Lions can run faster than house cats, while a scaled-up house cat would have to be slower, due to the square cube law. hence the lion obviously has more muscle mass. In the case of speed, up to a certain point it is possible to increase muscular force that way, jsut as much as weight, and at the same time have a greater stride lenght. after that point, animals get slower (lion>housecat>elephant). Depending on the biology, there is a lot of room here (eg. blue whales are very fast creatures).
I see no reason to assume Spinosaurus would necessarily have a weaker bite.

imo a bite force of 2t, maybe more, is fully possible for a large Spinosaurus. Their skulls were not built to do mechanical damage, or produce particularly huge forces of course, but gripping requires strenght too, and they were certainly not weak.

[Grey]

I'm not fully convinced yet. I usually thought that after reading some posts from TheROC, but the opinion of Sakamoto in several posts on Askabiologist threw cold water on this.

I really hope, and I think this likely, that a study about this will come sooner or later, then we'll have something closer of an idea and a consensus.

[theropod]

Sakamoto's own figures suggested a decent bite force and he never gave a definitive figure on Askabiologist if I remember right. He may have been speaking in relative terms and/or guessing.

[creature386]

Has this been posted yet?
www.tandfonline.com/doi/abs/10.1671/0272-4634(2007)27[892:FMOSCD]2.0.CO;2#.Ua4gCeAoKUO

[Fragillimus335]

Jun 3, 2013 19:57:13 GMT 5 Grey said:

I'm not fully convinced yet. I usually thought that after reading some posts from TheROC, but the opinion of Sakamoto in several posts on Askabiologist threw cold water on this.

I really hope, and I think this likely, that a study about this will come sooner or later, then we'll have something closer of an idea and a consensus.

First of all we need to get some complete Spinosaurus skulls into public collections!