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Tyrannosaurus en pointe: Allometry minimized rotational inertia of large carnivorous
#1
M Henderson, Donald & Snively, Eric. (2004). Tyrannosaurus en pointe: Allometry minimized rotational inertia of large carnivorous dinosaurs. Proceedings. Biological sciences / The Royal Society. 271 Suppl 3. S57-60. 10.1098/rsbl.2003.0097. 

Abstract

Theropod dinosaurs attained the largest body sizes among terrestrial predators, and were also unique in being exclusively bipedal. With only two limbs for propulsion and balance, theropods would have been greatly constrained in their locomotor performance at large body size. Using three-dimensional restorations of the axial bodies and limbs of 12 theropod dinosaurs, and determining their rotational inertias (RIs) about a vertical axis, we show that these animals expressed a pattern of phyletic size increase that minimized the increase in RI associated with increases in body size. By contrast, the RI of six quadrupedal, carnivorous archosaurs exhibited changes in body proportions that were closer to those predicted by isometry. Correlations of low RI with high agility in lizards suggest that large theropods, with low relative RI, could engage in activities requiring higher agility than would be possible with isometric scaling.

https://www.researchgate.net/publication..._dinosaurs
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#2
In don't like Henderson. ....
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#3
(03-12-2019, 06:19 AM)Melanosuchus Wrote: In don't like Henderson. ....

What you personally don't like Henderson?
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#4
Because this: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6098948/

Many researchers criticized his work because he did not take into account the specific bone density of spinosaurids.

Some paleontologists here in Brazil have asked him the model of the computer program he used in his article to try to use it in the species we have in the country.

What did he do? He asked for the data from Angaturama, but said he would not pass his software.  

So his work on the spinosaurus was done with a computer program he created but thet he doesn't allow that other scientists to use and test it. No one can replicate the results. This is not scientific.


Better explained: https://www.quora.com/Is-it-now-impossib...emiaquatic

Quote:I guess you are referring to the recent paper by Henderson argued that Spinosaurus was not adapted for semi-aquatic life style, right?
That paper is trash and very much flawed, the model they used for the buoyancy test has wrong proportions and is assumed to be the normal theropod density just like normal birds; which is wrong since Spinosaurus and closely related species have thicker bones than other theropods, see the picture (though that is not Spinosaurus but a closely related taxon)
[Image: main-qimg-68082fa8a311d85d4420a6ee5bf6bda7]
Picture from Aureliano et al.2018
So those thicker bones means it would be heavier per volume than other theropods, that means denser, so treating it as having the same density as birds is wrong and together with the wrong proportions makes the results of the paper rather questionable.
He does consider it in a sentence in the end of the paper, that pretty much says if the density is different his model may be flawed and Ibrahim’s (semi-aquatic) version is the correct one, ironic isn’t it?
Other invalid argument from Henderson is that if it was truly semi-aquatic not only it would have had shrunken legs but also shrunken legs and the post 2014 reconstruction still has large arms. We still haven’t found arm bones from so that part of Ibrahim’s model is speculative and should be not taken as a rule, so you can’t use his model arm size to say it is not semi-aquatic.
It has otter inconsistent arguments but I’m not detailing those here because this would go too far, but I’ll still quote those:
  • Arguing for Spinosaurus having the same kind of respiratory system as a modern bird but criticizing the 2014 composite that at worse is cross-scaled from some closely related species.

  • Arguing Spinosaurus could not dive because it was less dense than water. Me and you are less dense than water but we can dive because of muscle movement, same is valid fro Spinosaurus.
A quote from the theropod specialist Andrea Cau explains most of the story:
“There is a series of somewhat weak points in the Henderson paper on Spinosaurus. First, it is mostly based on the lateral view of the reconstruction in Ibrahim et al. (2014), which is far from being a definitive and accurate depiction of Spinosaurus anatomy. I feel that too much people have been overrating the actual importance of that figure, which is just a drawing of the known bones. Nothing in the known elements prevents Spinosaurus from having a different body shape. The dimensions and proportions of both forelimb and tail are actually unknown, and this biases significantly any possible estimation. The author notes this at the end of the paper... so, in short, what this paper discusses is the aquatic properties of a hypothetical reconstruction. There is an important element that the new paper ignores. The Henderson model does not take into account the wide ribcage that we must assume from Stromer's holotype, and used a too narrow animal model. One interesting point - that I agree - is that the quadrupedal hypothesis is not necessary for explaining the bizarre body proportions (once we assume as valid and not due to a composite). In any case, even dismissing the ability to fully submerge, this does not invalidate a semiaquatic ecology for this animal. If Spinosaurus was not semiaquatic, what is the reason for naris retraction, snout shape and elongation, tooth morphology, isotopic analyses, reduction in vertebral pneumaticity, reduction of accessory vertebral articulations, reduction in limb cavitation and foot morphology?”
The last part emphasizes reasons why Spinosaurus is most likely a semi-aquatic animal.
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