Theropod non-locomotory limb function

[Infinity Blade]

Just worried it wasn't robust enough evidence.

[Infinity Blade]

theropod
Verdugo

Dr. Carpenter replied.

[Verdugo]

Infinity Blade
He replied it much quicker than i thought. Too bad, he did not answer all of your questions but i think he did answer the most important one. I suppose that how he came up with the 1 tonne number for the muscle forces. If you just take the cross-sectional area that he suggested there and times it to the the isometric stress (5 kg/cm2 as suggested in the study, though i feel like this value may be a little too high) you will get it about 1 tonne. But yeah like i said, it's merely just the muscle force, it does not actually tell you how much the animal can actually lift if you do not take into account of level arms (it's the same how jaw muscle force wouldn't let you know how hard the animal can bite, you need to know the jaw muscle in-level and the out-level bite position). In the study, the leverage of the biceps is 0.094, if we just assume the same leverage for all elbow flexors:

Lifting strength (elbow flexor only) = 245 * 5 * 0.094 = 115 kgf

About Rothschild, yeah i don't see any reasons why you should delete it in the first place. If Rothschild examined the fossil first hand and he thought the damage was probably done by manus claws then that it's probably the case. However, judging by the position of the injuries, i don't think the other T-rex actually actively clawed this one in the face. It's more likely that this T-rex tried to attack the other one (probably at the neck), the other T-rex defended itself by clawing back.

[Infinity Blade]

However, judging by the position of the injuries, i don't think the other T-rex actually actively clawed this one in the face. It's more likely that this T-rex tried to attack the other one (probably at the neck), the other T-rex defended itself by clawing back.

Yeah, I agree. I don't think it would ever make sense for a T. rex to use its arms before it bites down on another animal, assuming it used its forelimbs as weapons. But using them to claw at something attacking the general vicinity of the forelimbs would make sense.

[Verdugo]

Burch (2015) Rigorous study on Theropod forelimbs osteology and myology

When considering the sum of the changes that have occurred in the musculature of the
tyrannosaurid pectoral girdle and forelimb, several patterns begin to emerge relating to the
function of the limb. At the shoulder, alterations in the origins and insertions of the Deltoideus
musculature and Scapulohumeralis posterior all emphasize extension of the humerus. Although
anterior excursion of the biceps tubercle of the coracoid suggests some importance of flexion of
the humerus, other modifications of the Supracoracoideus complex and Coracobrachialis indicate
a general reduction in this action among tyrannosaurids. A trade off between antagonistic actions
also seems to occur between adduction and abduction of the humerus, with evidence of emphasis
on abduction (Supracoracoideus) and a concomitant reduction of adduction (Subscapularis). At
the elbow, the retention of a well developed Triceps brachii and modifications of Supinator
suggest that flexion and extension likely retained importance, and were potentially even
emphasized, in tyrannosaurids. Although the movements of the wrist would have been restricted
relative to those of basal theropods based on the osteology of the carpus, there is little evidence
that the musculature acting on the wrist would have been reduced. Finally, the morphology of the
unguals indicate that digital flexion would only have been limited in the most derived
tyrannosaurids.

_ Strong shoulder extension (retraction), weak flexion (protraction)
_ Strong shoulder abduction, weak adduction (contrary to Lipkin & Carpenter 2008)
_ Strong elbow flexion and extension
_ Wrist muscles are not reduced
_ Digital flexion is reduced in the most derived taxa (Tarbosaurus baatar)

[Verdugo]

theropod Infinity Blade

Do you guys happen to have forelimbs data (bone length and midshaft width) of Theropod such as Megalosaurid, Spinosaurid, and Dromaeosaurid? Would love to see how they compare to each others using the methodology i posted before.

Also, i have figured out way to actually quantify (approximately) Theropod's prey size based on their forelimb strength. I compare their forelimb strength to Ursid to work out the size of prey that they can possibly restrain. I suspect Spinosaurid to score particularly high in this regard. In fact, i think their forelimbs may be even strong enough for quadrupedalism. But yeah i would need some data

Thanks in advance.

[dinosauria101]

Oct 30, 2019 20:20:59 GMT 5 Verdugo said:

In fact, i think their forelimbs may be even strong enough for quadrupedalism. 

Hasn't that already been proven for Spinosaurus?

[Infinity Blade]

Not by a longshot. Although, I’m interested in seeing what Verdugo can do with megalosaur forelimb data. Currently I’m not aware of any.

[dinosauria101]

^Was that directed at me?

[Infinity Blade]

Yes. No proof for Spinosaurus being quadrupedal.

[theropod]

Verdugo I don’t know any, but I’ll check the literature. If I find any, I’ll let you know. Otherwise, you may still be able to get at least an idea based on measuring the midshaft diameters in published figures, which should be available for a whole range of relevant taxa.

EDIT:
Deinonychus AMNH 3015:
HUMERUS:
Length
L 227.0
R 237.0*
Least diameter of
shaft
L 18.0
R 18.2
from Ostrom, J.H. 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Peabody Museum Bulletin 30: 1–165.

[theropod]

Something my supervisor mentioned in class yesterday: That tyrannosaurid or abelisaurid scapulocoracoids aren’t reduced despite the small forelimbs probably has developmental reasons, as the shoulder girdle and forelimb develop from proximal to distal.

[Verdugo]

Oct 30, 2019 21:05:54 GMT 5 theropod said:

Otherwise, you may still be able to get at least an idea based on measuring the midshaft diameters in published figures, which should be available for a whole range of relevant taxa.

Well, obviously it would still be better to have the listed measurements than to pixel-measure it. The point is i want to keep my personal biases to minimum. But anyway, that Deinonychus one is good, thanks for posting it.

If you have data of non-carnivorous Theropod like Therizinosaurus or Deinocheirus, please post it too. I'm not looking for just the Carnivorous ones, the more the merrier.

---

Dinosauria: AFAIK, the fossilised remains of Spinosaurus's forelimbs are a bit lacking

You really cannot prove anything without any fossilised remains to work on... (that's why i said Spinosaurid, not Spinosaurus)

Also, osteology and myology studies of Spinosaurid's forelimbs are pretty much non-existent. I can sort of work out the bone strength and guess how the muscles may attach by looking at its forelimbs but even so, i don't know about its possible range of motions. So even if i can quantify that the forelimbs are strong enough for quadrupedalism, i still don't know if its ROM is sufficient for such task.

[Infinity Blade]

Oct 31, 2019 17:43:03 GMT 5 theropod said:

Something my supervisor mentioned in class yesterday: That tyrannosaurid or abelisaurid scapulocoracoids aren’t reduced despite the small forelimbs probably has developmental reasons, as the shoulder girdle and forelimb develop from proximal to distal.

Would this still translate to some actual, practical function in life? I imagine the answer is still 'yes', but just to be sure.

Edit: interestingly it seems like there is indeed some scientific literature that suggests the coracoid could have been anchoring neck muscles, something I've only heard in passing on websites or blog post comments previously.


From The Age of the Dinosaurs in South America->

[theropod]

Yes, of course that doesn’t change anything about their function, it’s just an explanation that doesn’t require said function to be particularly important on selective grounds.