Giant theropods overview thread

[blaze]

The minimum estimate still leaves up to half the height of the tall spines of the tail and doesn't fallow the curve of the vertebral column, you could have used his Baryonyx for reference, using that I got a total difference in area of less than 8% even including arms and legs, compared to the 18% in your minimum version, it was pretty close in the neck and back, the difference was in the tail. Also, what is the point of the liberal one? will the spines really make that much of a difference? they are about 3cm wide at the base and 2cm close to the top.

I suppose the width comparison of the snout didn't convinced you that the holotype dentary scaled to any other size is too big for the morrocan rostrum.

Edit: it seems my answers are in the spinosaurus v tyrannosaurus thread on cf.

[theropod]

Does that dentary really look so gargantuan to you when scaled at 136%?

Surely, that is a deep-jawed creature (even Irritator is btw), and there are good reasons for it to be. I actually find the size of the dentary much more notable in the lateral aspect than in the dorsal one. But what is there to it that makes it so unfeasible, even less reasonable than the restoration below, when all we’d have to assume was that this creature had the mandibular proportions of a baryonychine, but a more robust jaw?


btw I’m not the first to suggest such a large dentary, just the first receive so much attention:

done by MysteryMeat from CF, here the difference seems to be over 40%, although I can see how that dentary may be a tad too big.

It seems a whole lot more feasible than the version I posted above. Also note that I redit my restoration from scratch for not fewer than three times, and all the times it turned out like that (not exactly of course, but at least).

Dal Sasso et al.’s difference is ~37%.

Even this juvenile specimen, although much more gracile, seems to demonstrate it:



Headden scales them somewhat differently in his scale chart and skull restoration, in one? the dentary is longer than the rostrum, in another? a good deal shorter.

Either way, I think I have a fairly good basis for my claim. Of course you don’t have to agree.

Regarding the bulk of the tail, I’ve already checked and it was just a 1.2% difference when removing that with the alignment.
How does the black outline (see here?) reach even close to half the height of the neural spines? The dark grey one surely does, that’s why it is the liberal one.

[blaze]

Yes, for one the tip of the dentary ends up 17% wider than the premaxilla and the teeth are just as big as those of the premaxilla judging by the size of the alveoli, they'll clash with one another, could it even close its mouth?

How do you know Irritator was deep jawed? it doesn't preserve most of the dentary nor the angular or are you talking about the posterior part of the mandibles?

edit:

look how much of that skull is restored, can you really trust the size of the premaxilla and the length of the jaws?

I didn't realize that MisteryMeat had meade the dentary that big before, it used to look fine to me but not after a realized how wide is the jaw ending up, how weird is it that is the upper jaw occluding into the lower jaw? except for the tips of course.

edit2:


The profile of the tail and neck were based Baryonyx and in the case of the tail it corresponds with the part of the spine were it has a "pinch", becoming narrower from there on, I used that and the height of the ilium for the profile of the back, the white line corresponds to height of centrum up to the pre and postzygapophysis of the vertebrae.

It is about 13% less than your version, and yes, there's parts of the tail in your version where you left about half the length of the spine, in the posterior part of the first half of the tail

[Deleted]

Feb 11, 2014 3:53:57 GMT 5 blaze said:

Yes, for one the tip of the dentary ends up 17% wider than the premaxilla and the teeth are just as big as those of the premaxilla judging by the size of the alveoli, they'll clash with one another, could it even close its mouth? 

MSNM v4047 would likely just have a proportionally narrower mandible and proportionally smaller teeth(Why do you have to mention teeth? They are no good for size estimations!)than IPHG 1912 then. Nobody is suggesting that MSNM v4047's jaw would be an exact replica of IPHG 1912's jaw except larger.

When using other specimens to fill gaps, there are always modifications made to have them fit in. The notion that each individual is unique isn't exclusive to humans, you know?

And as for the back profile, I think the spines would uplift the back quite a bit(around ~30-33% of the spine height imo, give or take) so the back would end up higher than the hips.

[blaze]

I didn't mention the size of the teeth as reference for the size of anything other than the fact that both teeth will have similar sizes making even more difficult for them to occlude in some way.

Of course not every specimen is an exact copy of another but just look at the differences here, they are not relatively small difference in shape and proportions but big difference between specimens not so far in size from one another, you know how much proportionally narrower will have to be to fit fine with the rostrum? just as much as theropod upscaled it to fit in length, we might as well say that MSNM v4047 is about the same size as the holotype, it just had a proportionally longer dentary. Then look at how wide the mandible is by the level of the posteriormost part of the rostrum, the mandibles are a 100% wider than the rostrum, I know theropod disagrees but right now I can't see how they are the same taxon at all, the actual skull of S. aegyptiacus was probably wider and proportionally shorter than that of the taxon represented by the rostrum.

The back outline, the extra height in a triagle form? the reason I prefer to ignore that part is because if you count it you are including a lot more volume that they would have actually contributed, at least in the way theropod calculated the volume this time, the torso and the hips of spinosaurus were certainly over 1m wide but the ridge? the spines themselves are only about 3cm wide at the base and the distance between the transverse processes of the vertebrae are what? 20cm maybe a little more? could the ridge be any wider than the transverse processes of the vertebrae?

[theropod]

has anyone seen this?
qilong.tripod.com/Spinosaurs/spino.html

I would rather use Suchomimus/Cristatusaurus than Baryonyx. That the dorsal structure added no more than in a theropod with close to average neural spines doesn’t seem reasonable (not even if it was a "sail", let alone shaped like a chameleon’s back).

In bisons, the width of the hump definitely isn’t constrained by the width of the transverse processes. Jackson’s chameleon osteology doesn’t appear well-documented enough to tell.

As I wrote, I find the dentary depth much more impressive than the fact that the teeth would be large, but I don’t see why it is so unreasonable--those in Spinosaurus’ mandible are large, and for a good reason. They had to withstand the weight of really big fish on a daily basis, otherwise we wouldn’t be finding spinosaurine and Onchopristine remains next to (or in) each other all the time.

Taxonomically, I think MSNM V 4047 is most likely the same taxon as MHNM SAM Idontknowhwhatnumber (which imo corresponds well to IPHG 1912 VIII 19 in size). There is really no way to know whether they are Spinosaurus aegyptiacus or not, you can only see a morphological difference if you also have overlapping material, but the similar morphology of the teeth, the geographical range, size and abundance of such spinosaurine remains makes me fairly sure it is at least Spinosaurus.

[blaze]

The comment about the size of the teeth was the least important remark I made, I don't know why you are responding only to that rather than the 17% wider dentary at the tip and the 100% wider mandible at the posterior part.

In bison the width of the hump is restricted by the scapulae, which also cover a good chunk of the height of the spines, the spines are also more robust and expanded distally for the attachment of muscles, like those that go to the head and stuff, not really comparable.

I've seen other pages of that old website of Headden but I don't remember seeing that one page.

[theropod]

Dentary scaled at 136%, 120%, 111% and original size.


In terms of how the alveoli fit, obvious I can’t see them fitting perfectly anyway (which I also doubt would work with unedited shots of other theropods, in the same species, sometimes even in the same specimen ), but the 136% version is definitely among the best. The alveoli overlap, but the teeth would not have to collide unless they were perfectly perpendicular and cylindrical. It seems all of them could manage to fit just next to the respective tooth of the other jaw.
Even crocodile mandibles? often bulge outwards to be broader than the rostrum, while they are similar in width at the dentulous part.
I don’t see how an animal actually apprehending its prey from a fairly tall stance could not be even more reliant on a well-developed mandible for prey aquisition.

There are other animals with really massive dentaries (which happen to have similar proportions!):

Tylosaurus isn’t even what one would call a massively strong biter, it, in fact, has a really elongate, ora-like skull and pointed, snake-like teeth.

Also, how realistic is the upper tooth row beeing more than 70% longer than the mandibular one? In Suchomimus, the difference is just 22%! And don’t the teeth look terribly undersized to you when keeping the dentary at original size? Actually, I do think the size of the teeth is not to be ignored, I just don’t see why there should be a vast disparity in size between upper and lower dentitions.
But I have no problem with dentary teeth being almost the same size as those of the rostrum, rather with dentary teeth looking like a quarter the size of the rostral ones...


I’m not assuming a bison-like hump. Bison aren’t just wider-bodied in general, their back has a rounded cross-section. If I was under that assumption for Spinosaurus, I’d have included the whole neural spine, not just a third or half of it.
imo the most logical restoration of a ridge-back in an extinct archosaur is this Arizonasaurus:

This also looks very similar to Jackson’s chameleon.

You might have noticed the strong resemblance between the spines of Arizonasaurus and Spinosaurus in terms of their elongation. Does anyone have a picture of a vertebra of this animal in anterior or posterior views?

[Deleted]

Feb 11, 2014 15:21:51 GMT 5 blaze said:

I didn't mention the size of the teeth as reference for the size of anything other than the fact that both teeth will have similar sizes making even more difficult for them to occlude in some way.

Of course not every specimen is an exact copy of another but just look at the differences here, they are not relatively small difference in shape and proportions but big difference between specimens not so far in size from one another, you know how much proportionally narrower will have to be to fit fine with the rostrum? just as much as theropod upscaled it to fit in length, we might as well say that MSNM v4047 is about the same size as the holotype, it just had a proportionally longer dentary. Then look at how wide the mandible is by the level of the posteriormost part of the rostrum, the mandibles are a 100% wider than the rostrum, I know theropod disagrees but right now I can't see how they are the same taxon at all, the actual skull of S. aegyptiacus was probably wider and proportionally shorter than that of the taxon represented by the rostrum.

The back outline, the extra height in a triagle form? the reason I prefer to ignore that part is because if you count it you are including a lot more volume that they would have actually contributed, at least in the way theropod calculated the volume this time, the torso and the hips of spinosaurus were certainly over 1m wide but the ridge? the spines themselves are only about 3cm wide at the base and the distance between the transverse processes of the vertebrae are what? 20cm maybe a little more? could the ridge be any wider than the transverse processes of the vertebrae?

The red part is easily attributable to the aforementioned individual differences. I seriously don't think the tooth issues mean much.

As for the green part, I think I agree somewhat with theropod, but I don't think MSNM v4047 is anywhere near ~250% the size of IPHG 1912 like he does. I think IPHG 1912 is around ~8-9 tonnes, give or take, based on what shartman said. theropod's ratio would not give a good result here. Big difference? Look how different various Tyrannosaurus and/or Allosaurus skulls can be from each other. MSNM v4047 being the same size as IPHG 1912 would give it quite a bit of an overbite, which I don't think is the case, given that virtually all known animals with expanded jaw tips pair the upper and lower expansions together.



Now for the blue part. I think the muscle is only a bit wider than those transverse processes, most of the ridge volume is fat. If I could be bothered, I'll make a reconstruction of what I think Spinosaurus is like in cross-section. Think of something like Arizonasaurus, with a relatively smooth meld between the ridge and the back.

[creature386]

theropod
You said MNHN SAM 124 is comparable in size to the holotype, but if that's true, won't it rather be like 165% the size? (600 mm/988 mm = 1.65)
I don't know if the dentary or the rostrum is 600 mm long, but given that the former is very fragmentary, I think it's the rostrum.

EDIT: I forgot the source: qilong.wordpress.com/2011/10/07/for-a-few-spinosaurus-more/

[theropod]

MNHN SAM 124 is not as complete as MSNM V4047. I was speaking in rough terms of course, the width of the rostrum fitted to the dentary of the Spinosaurus holotype seems to roughly correspond to the width of MNHN, but I didn’t even measure it, and of course they don’t have exactly the same proportions either.

[creature386]

But even when it are rough terms, 165% vs 250% is quite a difference. Normally, measuring errors merely influence the result by 10-20% up or down, but here the difference is more than 50%. It is not as complete, but 600 mm probably came from comparing the elements of both and comparing them is what I was doing in my post.

[Deleted]

Feb 11, 2014 19:50:07 GMT 5 creature386 said:

But even when it are rough terms, 165% vs 250% is quite a difference. Normally, measuring errors merely influence the result by 10-20% up or down, but here the difference is more than 50%. It is not as complete, but 600 mm probably came from comparing the elements of both and comparing them is what I was doing in my post.

Dude, the ~250% is volume, not linear difference like your 165%. You do NOT compare linear dimension differences to volumetric differences like that. It's more like ~449.2% vs 250% actually.

[creature386]

Sorry, it looks like my number is even more exaggerated then.

[theropod]

Feb 11, 2014 19:50:07 GMT 5 creature386 said:

But even when it are rough terms, 165% vs 250% is quite a difference. Normally, measuring errors merely influence the result by 10-20% up or down, but here the difference is more than 50%. It is not as complete, but 600 mm probably came from comparing the elements of both and comparing them is what I was doing in my post.

The difference is 136% and 165%, which I think is mainly because MNHN SAM 124 would have been about 10 centimetres or so longer if it was as complete as MSNM V4047. Roughly comparable to the size the rostrum of IPHG would have had, if it was scaled like in the above comparison.

I’m not mad, I don’t think MSNM V4047 was 35m long lol