Underrated giant theropods

[Cross]

Is rib articulation to blame for the narrow torso of MOR 555? It kinda surprised me that it was just ~6 tons along with NCSM 14345 in Bates et al (2009).

By the way, I noticed that people commonly discount Allosaurus in discussions about the largest theropod dinosaurs. And no, I'm referring to Allosaurus as a genus, not specifically Allosaurus fragilis or Allosaurus lucasi. I'm aware that the majority of specimens are just in the ~8-9 meter range, but based on the material referred to Epanterias (and if you're a lumper, Saurophaganax too), it seems that some species/individuals could also get 11-12m. There are also colossal ichnotaxa that seem referable to Allosauridae (theropod has talked about these before).

Heck, we may just be underestimating the diversity of Allosauridae as a whole, not just the genus Allosaurus itself.

[blaze]

spinodontosaurus
Torso length, I didn't consider tip to tip length because the other specimens have different proportions of the head and tail length when compared to Sue. How did you estimate the width of Hutchinson et al scans? I got 155cm for Sue vs 149cm for CM 9380, that's 96%, though it is important to mention that the top view scans in the publication don't seem to be in orthogonal view.

Yeah, we've gone off topic, this however elucidates something about Bates et al (2009), they indeed went overboard with those thighs so this means a probably sub 6 tonnes weight for Fran.

Cross
It doesn't seem like Allosauridae is really that diverse, depeding on who you ask it includes 1 or 3 genera though it is possible that there's only 1 and with the identification of Upper Jurassic carcharodontosaurids in Africa I don't think there's any good reason why that ichnotaxon has to be an allosaurid.

[Deleted]

Jul 18, 2015 21:01:06 GMT 5 blaze said:

they indeed went overboard with those thighs so this means a probably sub 6 tonnes weight for Fran

Not really.

Those dorsal spines it has would likely be buried in the back, while in the paper, they reconstructed it with little flesh despite the actual structure of the spines resembling that of certain high-spined bovids rather than chameleons or something.




So just move the extra thigh mass into the back, no need for downsizing of any kind. If anything the excess thigh mass may not even be enough, but that's just based on eyeballing the model.

Also, who's to say that you would even be able to see a ridge at all on a living Acrocanthosaurus? It could have just raised the back height like with ornithopods.

[blaze]

Cross
I forgot about what you asked of MOR 555, yes, as mounted, not only is the ribcage only as wide as the skull but it starts below the 6th dorsal rather than the 2nd.

@brolyeuphyfusion
Remember that the spines in the mount are too tall.
Anyway, well see, I'll try to do one of Fran too.

[theropod]

They also shrinkwrapped the neck terribly, but they did something similar with MOR 555.

We can make an estimate as to how much more mass a properly fleshed out ridge would add, simply by taking the ratio of the cross-sections, which is the same as the ratio between volumes, all else being equal.
By giving it a triangular, tapering shape in anterior view, I got an area about 6% bigger for the torso, implying a 6% higher volume for the axial segment (neck-torso-tail). That’s ~0.236m³ or ~250kg of additional muscle (following the density of 1.06 for skeletal muscle from Snively et al. 2013), I doubt reducing the size of the tighs will reduce the mass by much more than that.

They didn’t seem that outsized to me anyway, they just always look sort of cumbersome in those models because they protrude so abruptly.

[blaze]

The difference between the hip region of Bates et al. model and my GDI is over 500kg. In their model of Fran the hips are ~1.4m wide, for comparison the distance from femur to femur is ~90cm and the ribcage is ~1.3m.

[Deleted]

Jul 18, 2015 22:50:31 GMT 5 blaze said:

The difference between the hip region of Bates et al. model and my GDI is over 500kg. In their model of Fran the hips are ~1.4m wide, for comparison the distance from femur to femur is ~90cm and the ribcage is ~1.3m.

I measured the width of the (skeletal, not fleshy) hips + the femurs in the model and got ~1.1 meters assuming a ~1.3-meter ribcage, are you sure you didn't accidentally mismeasure?

[theropod]

He probably meant the width of the overall segment, including the thigh muscles.
It shouldn’t come as a surprise that this region will, and should, seem proportionately wider in a narrow-bodied carnosaur than it does in a tyrannosaur though. There isn’t any reason why these muscles should be narrower just because the ribcage is, they don’t attach to it after all.

[Deleted]

Jul 18, 2015 23:30:52 GMT 5 theropod said:

He probably meant the width of the overall segment, including the thigh muscles.
It shouldn’t come as a surprise that this region will, and should, seem proportionately wider in a narrow-bodied carnosaur than it does in a tyrannosaur though. There isn’t any reason why these muscles should be narrower just because the ribcage is, they don’t attach to it after all.

I know, but it doesn't look like that the difference due to slightly smaller thighs is anywhere near ~500 kilograms.

[theropod]

As I wrote, I don’t think the thighs are that unrealistically big either, they just seem so wide because the narrower ribcage. The thigh muscle should be just as extensive mediolaterally as in tyrannosaurs of equal size, just slightly shorter anteroposteriorly.

Actually, considering the unique femoral head morphology to allow for a greater lateral excursion, it could be argued that femoral abductors could also be bigger, which would increase the width.

[blaze]

I meant the thigh muscles, we were discussing if the thighs were reconstructed too big, no? still, broly, you seem to have measured the muscles of the shank seen through the transparent thighs rather than the femur, that's the discrepancy between my femur to femur measurement of ~90cm and yours of ~1.1m.

Seeming proportionally wider is one thing, being absolutely wider than the torso is another. The torso is not that narrow, if I include the flesh it's 130cm, Hartman's top view of Giganotosaurus is ~134cm. Slightly smaller thighs is an understatement, the muscle given to the thighs is twice as thick as the proximal femur width and they get wider the further away they are from the femur. Bates et al. (2009) estimate of Fran's thighs is 1328kg, that's higher than Hutchinson et al. (2011) estimated for the thighs of Sue (1287kg) and 300kg to 400kg more than their estimates for Stan/MOR and CM 9380 respectively.


Edit: But I'll give it the benefit of the doubt, comparing Hartman's skeletals it seems Fran the holotype of Giganotosaurus have very similar thorax length even though the later has a deeper one and the longer (in lateral view), bigger ribs gives me the impression that it's ribcage must be wider but without measurements we can't know for sure.

[theropod]

Bates et al. estimated the thigh segment of Fran at 663.709kg (×2=1327kg), while estimating the thigh segments of MOR 555 and BHI 3033 at 688.552 (×2=1377kg) and 743.937kg (×2=1488kg) respectively– just slightly higher (4 and 12% respectively), as they should be.

So I guess based on that, all the estimates from Bates et al. 2009 would have to be lowered.

[blaze]

I clearly wrote that I was comparing them to Hutchinson et al. (2011) estimates, Bates et al. (2009) seems to have categorically overestimate the size of the thighs, didn't I already mentioned that their thighs for Stan were over 500kg bigger than suggested by the GDI I did?

[theropod]

Oops, sorry, I overlooked CM 9380 and thought you were just referring to sue.

What I meant to say is that those thigh-muscle estimates are fairly consistent within the study, but I guess we’re already on the same page on that.

[blaze]

Yes haha, I agree.