Theropod non-locomotory limb function

[Infinity Blade]

On Lipkin & Carpenter (2008): I didn't read the paper in detail yet, but there are some figures in Lipkin & Carpenter (2008) that have me confused.

First they say:

An average strength of 5 kg/cm2 per cross-sectional area of muscle was used to determine the cross-sectional area of the M. biceps in Tyrannosaurus (Carpenter and Smith 2001). The NWR of the tendon tensile strength for the radius and ulna were added together to get the MF: 1357 N + 2133 N = 4490 N (356.12 kg). The formula used to determine the cross-sectional area of muscle is MF (kg)/strength (kg x cm^-2) = cross-sectional area (cm²). Thus, the estimated cross section of the Tyrannosaurus M. biceps is 356.12 kg/5 kg x cm^-2 = 71.224 cm². This translates into a diameter of 9.52 cm. Of course the M. biceps is not the only arm protractor. In fact, by using half the estimated cross-sectional area of the upper arm (based on a diameter of 25 cm), the amount of force generated is estimated to have been around 1150 kg, or 11,270 N. Of this, the biceps generated about 40%, and thus was a major muscle.

Next:

Next we evaluate the force at the elbow joint. The sum of the MFs (NWR + MWR) at the radius (138.3 kg) and the ulna (217.5 kg) minus the RF at the manus (33.5 kg) must equal the force at the elbow for a static configuration. Therefore, Tyrannosaurus has a force of 138.3 + 217.5 - 33.5 = 322.3 kg at the elbow joint for the NWR. This compares with a force of about 128.25 kg at the elbow joint of an average adult male human for the NWR.

I can see where this comes from. Earlier they calculated NWR for the radius to be 1,357 N; this would indeed translate to ~138.5 kg of force (when rounding; also, 1 kg = 9.8 N) for the radius. They calculated NWR for the ulna to be 2,133 N; this would indeed translate to ~217.7 kg of force for the ulna (again, when rounding).

And then there's table 10.2, which Verdugo alluded to.

I'm a bit confused. Again, didn't read the full paper in detail yet, but how did they get the figures in table 10.2? And what's this >1t figure for? The upper arm? I guess I'm just confused on how strong they think the whole arm of Tyrannosaurus was.

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fully developed tridactyl manus.

There was an intriguing explanation for a didactyl manus as opposed to a tridactyl one in T. rex. The "slasher" hypothesis-> that came out a couple years ago suggested that by getting rid of one functional digit, increased (50%) more pressure could be applied to each remaining claw. Less digits for holding onto prey, but I guess better for cutting deeper into prey.

Of course that's just an idea, but still.

[Verdugo]

Oct 25, 2019 17:46:12 GMT 5 theropod said:

Compared to other theropods in a similar weight class. Large Allosaurs and Megalosauroids. Those have larger, more robust forelimbs, larger ranges of motion (at least Allosaurus and Acrocanthosaurus, none of the others have actually been studied), larger muscle insertions (deltopectoral crest, , olecranon), larger claws and fully developed tridactyl manus.

Okay, first with Allosaurus. According to your image comparison and Carpenter (2002), Allosaurus clearly does not have a larger range motion than that of T-rex. It's longer and better positioned for reach but that is not the same as having 'larger range of motion'. Refer to Carpenter (2002) who clearly stated that T-rex had better range of motions:

In Tyrannosaurus, the humeral head is almost a hemisphere
(CARPENTER & SMITH 2001), thus the potential range of
motion is considerably greater than for many theropods (textfig.
12 E, 13 E).

Carpenter (2002) also pointed out that T-rex is more adapted than Allosaurus at adducting and protracting its forelimbs due to having larger coracoid. Also, its forelimbs are more robust:

In contrast to Tyrannosaurus and Deinonychus, the coracoid
of Allosaurus is proportionally smaller (text-fig. 12 C, 13
B) indicating that the forelimb protractors and adductors had
less mass. The scapula is elongated indicating that most of the
forelimb muscle mass was in the retractors. The arms are relatively
long and robust, although not as proportionally robust as
in Tyrannosaurus. The range of motion indicates that the arms
could grasp moderately large prey and pull it towards the body.
At present, there is no evidence indicating that Allosaurus
preyed on large sauropods as is often illustrated.

Also, are there any Theropod's forelimbs robusticity data at all to make quantitative comparison? I don't recall seeing a lot about that. However, when i use humerus circumference divided by length in T-rex, the data suggests that T-rex's humerus is more robust than those of Smilodon and Ursids that i know of.

Acrocanthosaurus clealy has robust forelimbs and pectoral girdle, so i suppose the arms must be very powerful. But i haven't seen any studies on the pectoral girdle (scapula + coracoid) of Acrocanthosaurus so that is just my guesswork.

Megalosauroid's arms are clearly monstrous but i don't know any studies regarding their forelimbs biomechanics. If you know any please post.

Also, where did you get the stuffs on deltopectoral crest and olecranon process from? I don't know any studies that directly compare those points among Theropods. Based on my own eyeball skills, i don't see T-rex deltopectoral crest to be particularly underdeveloped.

Also, refer to this post by Infinity Blade:

Large tyrannosaurids, Torvosaurus, and Acrocanthosaurus occupy a region that is similar to that of large-prey-specialist cats, and are well separated from other theropods along the first two PC axes. Among both taxonomic groups, species occupying this region showed relatively short and robust forearms, as well as long olecranon processes, robust metacarpals, and large radial and metacarpal distal articular surface areas. Large-prey specialist cats were also found to exhibit increased humeral robusticity, and relatively large humeral epicondyles and distal articular surface area. These results suggest that some theropods can be classed as large prey specialists that used their forelimbs in prey capture. The grouping of tyrannosaurids with larger forelimbed taxa such as Acrocanthosaurus and Torvosaurus in the large-prey-specialist region supports previous hypotheses of a functional role for the reduced forelimb in prey capture. Early dinosaur taxa (e.g., Tawa) are grouped in the small-prey-specialist region, whereas coelophysoids show indicators that they may have had a diet of mixed-sized prey. The similarity in the patterns between theropods and cats suggests that theropods may have engaged in similar forelimb-based behaviors in predation, such as grappling with large prey or swiping at small agile prey.

One study has also argue that having less claws lead to higher pressure for penetration and slashing, though that study has not published yet. See Infinity post. More does not always mean better.

Also, can you at least provide sources for your claim that 'T-rex's forelimb is poorly suited for raptorial purposes' rather than just making some vague statements? Your whole argument is basically 'if you're not as good as the best, then you sucks' without taking accounts that T-rex's forelimb is still more adapted for tacking large preys than many other Theropods taxon. You may as well make nonsensical arguments such as Lions are poor grapplers because they are not as good as Carnivores of their size such Smilodon fatalis, without taking into accounts that Lions are still one of the top-tier grapplers and are known for grappling with large Bovids.

I'm in no way suggesting that T-rex has better forrelimbs than the Theropods that you mentioned, merely arguing against your claim that 'T-rex's forelimb is poorly (emphasis added) suited for raptorial purposes'

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Infinity Blade
Yes, i agree that the paper is a bit confusing with the way they presented things, it confused me at first too. Anyway:

You're right that the 300 kg figure is merely just the reaction force acting on the elbow caused by the Muscle force pulling upward at the insertion point and the reaction force pulling downward at the tip of the manus (to simulate T-rex trying to lift something by hooking its claws into). Tbh, i don't know what's that figure supposed to represent. I think they want to pointed out that T-rex has strong elbow or something but that figure is not obtained from the elbow morphology itself. Yeah, idk, it's not really meaningful to me tbh and it's certainly not Lifting strength. Also, you correctly pointed out that that figure is obtained from the sum of NWR Muscle force not NWR + MWR as the paper said.

The way they estimated the 1 t figure is really vague. I suppose they estimated it based on some estimated cross-sectional area times specific muscle force (5 kg/cm2) but they did not explain it in details. Regardless, it's just the Muscle force value and it's not Lifting strength (which is called Resistive force in the study). To calculate Lifting strength/Resistive force, you need to take in accounts of in-level arms (distance between elbow joint and Muscle insertion point) and out-level arm (distance between elbow joint and tip of the manus).

As you can see, the only meaningful value that i can think of are those in Table 10.2 which are actually Lifting strength assuming T-rex would hook into something with its claws and lift it up.

Because i have not seen Carpenter & Smith 2001 i cannot really compare the difference in methodology to see how they came up with the figures. Or the figure in Wiki is just bollocks and that 199 kgf figure never really exist.

[theropod]

Okay, first with Allosaurus. According to your image comparison and Carpenter (2002), Allosaurus clearly does not have a larger range motion than that of T-rex. It's longer and better positioned for reach but that is not the same as having 'larger range of motion'. Refer to Carpenter (2002) who clearly stated that T-rex had better range of motions:

The anterior range of motion Carpenter restored for Allosaurus is clearly greater than that for Tyrannosaurus, check Figure 13, which this drawing bases on:

As is that of Acrocanthosaurus, based on Senter & Robins’ reconstructed ranges of motion, which clearly state the humerus could swing anteriorly past the vertical.

T. rex does have a larger posterior range of motion, but I don’t see how that would be relevant for the raptorial capabilities of the forelimb. The two allosauroids that have been studied would both clearly have been able to reach downwards and forwards more effectively, which would be essential for grasping prey.

Carpenter (2002) also pointed out that T-rex is more adapted than Allosaurus at adducting and protracting its forelimbs due to having larger coracoid. Also, its forelimbs are more robust:

Yes but Carpenter evaluated them at unit humeral length. At unit humeral length that’s what, an 8 ton Tyrannosaurus being compared to a 2 ton Allosaurus? Of course the former has a larger scapulocoracoid than the latter, unless it is comically tiny for its body size.
When correcting for size, that’s not a forelimb "more adapted" for adduction and protraction, that’s simply a larger animal, with a correspondingly larger muscle mass on its pectoral girdle. The scapula and coracoid of Allosaurus are not small, they are in proportion to its body size. But they are smaller compared to its forelimb, because its forelimb is larger for its body size.
Acrocanthosaurus scapula and coracoid are quite similar to T. rex’ in size. Refer back to the comparison above. It was a long time ago, but I think I scaled them to unit humeral length there as well. Look at the difference between Allosaurus and Acrocanthosaurus in particular. The forelimb length is negatively allometric, the size of the scapulocoracoid is not (of course Acrocanthosaurus’ forelimb, while short, is still than that of T. rex, both relatively and in absolute terms).

Also, are there any Theropod's forelimbs robusticity data at all to make quantitative comparison? I don't recall seeing a lot about that. However, when i use humerus circumference divided by length in T-rex, the data suggests that T-rex's humerus is more robust than those of Smilodon and Ursids that i know of.

I’ll see if I can find any. At any rate, that comparison, is again not really that relevant, you are comparing it to a vastly smaller animal, with proportionately vastly larger forelimbs. Stop for a second to imagine what carnivoran forelimbs would look like if they were as robust as large theropod forelimbs.

Theropod forelimbs are obviously way more robust than those of carnivorous mammals, but they are also way smaller relatively speaking.

I was not talking about the strength its forelimb had in absolute terms, by which standard it should be clear it was quite strong (simply on account of everything you can compare it to in the extant world being less than a tenth its body size), I was referring to its predatory capabilities with respect to the size of the entire animal and it’s prey. We also aren’t evaluating T. rex capability to grapple with a zebra here. "Adaptations" are made to things an animal actually does (or tries to), not to different things another animal does. T. rex forelimbs would be quite poorly suited to "grapple" (or whatever we want to call what most theropods probably did with their forelimbs…"meat-hook"?) a Triceratops or Edmontosaurus.

T. rex’ forelimbs seem poorly adapted for raptorial purposes compared to most other theropods. This is due to a combination of their small size relative to body size and a general trend of reduction within the forelimb (less expansive attachment areas on the humerus, comparatively gracile forearm, didactyl, thereby gracile manus). For its body size, T. rex forelimbs are just not as well-adapted for use in predation as those of Deinonychus, or Allosaurus, or Torvosaurus or Acrocanthosaurus, to name but a few examples.

All of these are animals that we can expect used their arms in an at least somewhat significant role. Because they are much larger for a given body size and/or have morphological adaptations far more optimized for raptorial purposes, as I have outlined before (larger claws, more strongly developed hands, larger reach, larger muscle insertions on the forelimb). Since it is usually other theropods we are comparing T. rex to, yes, it is accurate to say that T. rex forelimbs were poorly suited for raptorial purposes compared to these taxa

Megalosauroid's arms are clearly monstrous but i don't know any studies regarding their forelimbs biomechanics. If you know any please post.

No, there aren’t any studies on megalosauroid forelimb biomechanics. Curious, considering how many there have been on the forelimbs of T. rex. There doesn’t seem to be a comparable research interest in them, despite the forelimbs clearly being more important for prey acquisition in these taxa.

But this is the humerus of the Baryonyx holotype (~2-3 t specimen?) compared to the humerus of sue (8t+ specimen) at equal length, and their actual relative sizes:

(note that Sue’s humerus is unusually robust for a T. rex, most are much more slender)

It is beyond clear that Megalosauroid forelimbs are more robust, and have larger muscle insertions compared to tyrannosaurid forelimbs, even at the same humerus length, let alone similar body sizes.

Also, where did you get the stuffs on deltopectoral crest and olecranon process from? I don't know any studies that directly compare those points among Theropods. Based on my own eyeball skills, i don't see T-rex deltopectoral crest to be particularly underdeveloped.

"The humerus is slender, and the deltopectoral crest is weakly developed in all tyrannosauroids except Eotyrannus (fig. 5.15)." "The olecranon process is moderately well-developed but short (fig. 5.16)."
From Holtz 2004, p. 123.

Besides, it’s not that I’m unable to go and look at a theropod forelimb when I want to.

One study has also argue that having less claws lead to higher pressure for penetration and slashing, though that study has not published yet. See Infinity post. More does not always mean better.

Yes, and for all that abstract suggests, the author didn’t even look at whether the digits were strong enough to "slash" in the manner suggested (or whether the claws were suitable, which they probably weren’t). The force needed for a single claw to do this doesn’t get smaller just because there are less of them, and the strength of one digit doesn’t get larger either. That’s why the reduced manus of derived tyrannosauroids is likely a detriment to use in predation, it limits the force that can be applied through it, which is important if the forelimb is used to maintain a grip on a struggling prey item.

When you look at the hands of the T. rex and the Allosaurus in my comparison above, which one do you think can hold the larger load? Right, the Allosaurus, more fingers, more powerful antebrachium, larger claws. Now consider that the T. rex in question is 4 times larger, and would likely have to deal with far larger forces from its prey (or its own body mass) if it used its forelimbs in predation.

Also, can you at least provide sources for your claim that 'T-rex's forelimb is poorly suited for raptorial purposes' rather than just making some vague statements?

I tend to be quite meticulous about avoiding vague statements. I’m sorry if this one turned out to be too vague for your taste, but that was not due to lack of evidence, but because I thought it was fairly obvious. You had already quoted the comparison I made a few years ago, which clearly illustrated that, after all.

Your whole argument is basically 'if you're not as good as the best, then you sucks' without taking accounts that T-rex's forelimb is still more adapted for tacking large preys than many other Theropods taxon.

I also thought it was clear I was comparing it in the context of other theropods actually well-adapted for this. Again I am sorry if that was less obvious than I thought it was.

Charig, A.J. and Milner, A.C. 1997. Baryonyx walkeri, a fish-eating dinosaur from the Wealden of Surrey. Bulletin-Natural History Museum Geology Series 53: 11–70.
Brochu, C.A. 2003. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. Journal of Vertebrate Paleontology 22 (sup4): 1–138.
Holtz, T.JR. 2004. Tyrannosauroidea. In: Weishampel, D.B., Dodson, Peter and Osmólska, Halszka (eds.), The Dinosauria, 111–136. University of California Press, Berkely, Los Angeles, London.
Senter, P. and Robins, J.H. 2005. Range of motion in the forelimb of the theropod dinosaur Acrocanthosaurus atokensis, and implications for predatory behaviour. Journal of Zoology 266 (3): 307–318.

[Infinity Blade]

Yes, and for all that abstract suggests, the author didn’t even look at whether the digits were strong enough to "slash" in the manner suggested (or whether the claws were suitable, which they probably weren’t). The force needed for a single claw to do this doesn’t get smaller just because there are less of them, and the strength of one digit doesn’t get larger either. That’s why the reduced manus of derived tyrannosauroids is likely a detriment to use in predation, it limits the force that can be applied through it, which is important if the forelimb is used to maintain a grip on a struggling prey item.

Hmm, are you talking about whether or not the flexor tubercles of the claws would give them sufficient power to cut through soft tissue or if the digits can slash without getting damaged? I originally thought the latter, but only just now did the former occur to me for some reason.

As for whether or not the claws were suited to slashing, a bunch of news articles reporting the abstract said something about sharp-edged "beveled" manual claws. For what it's worth, I actually emailed Dr. Stanley himself a while back (almost a year ago) to see if this was just something the media made up or whether or not this was actually true. According to him, it was true (attachment below).

I don't think I've actually taken a good hard look at actual T. rex manual unguals (or any good reconstructions thereof), though, so hearing this really piqued my interest and raised an eyebrow at the same time. I hope a full paper of this comes out.

[theropod]

That is really interesting, I wasn’t aware the bone core was showing signs of a sharp edge. Still would take it with a grain of salt though, dromaeosaur unguals are "beveled" as well, and yet most researchers seem to agree the horn sheath would not give them an edge sufficient to cut flesh.

[Infinity Blade]

Verdugo I sent an email to Ken Carpenter asking about the 2008 paper (and also the 199 kg bicep curl figure), just to be sure. We'll see if he can clear anything up, assuming he has the time to respond.

Still would take it with a grain of salt though, dromaeosaur unguals are "beveled" as well, and yet most researchers seem to agree the horn sheath would not give them an edge sufficient to cut flesh.

Even if it's not the primary function of dromaeosaur claws to cut, do you still think they could cut, though?

The most I've heard from scientists on this was (coincidentally, in light of the discussion above) by Ken Carpenter, where in a 1998 paper-> he says "A claw embedded in the skin would find it difficult to cut the thick hide; 4) although we do not know how sharp the keratin sheath of a dromaeosaurid claw was, it was probably less sharp than a dull knife because there was no way for the dromaeosaur to hone an edge (cats hone the tips of their claws on objects, such as furniture).".

The statement puzzles me because cats in the wild hone their claws on say, tree trunks, and IIRC they actually have some kind of cutting edge on the ventral surface of their claws; I don't see why a dromaeosaur couldn't do the same.

Now let me get this straight, I don't think cutting was the primary purpose of dromaeosaur digit II claws (I think, like cat claws, the ventral keels were primarily there to help puncture prey, which we discussed some pages back), but I do think the cutting edges could secondarily be used to fulfill such a purpose.

[Verdugo]

theropod

T. rex does have a larger posterior range of motion, but I don’t see how that would be relevant for the raptorial capabilities of the forelimb.

Posterior range of motion may be useful for pulling the preys back? Acrocanthosaurus has greater posterior range than Allosaurus as well, despite having similar anterior range.

Yes but Carpenter evaluated them at unit humeral length.

I suppose that may cause interpretation and conclusion not entirely meaningful due to the large different humerus length across different Theropod taxa. He should have scaled the forelimbs based on the perimeter that is more related to size such as femur length or total hindlimb length. Regardless, it does not disprove strong protractor, adductor, and retractor actions of T-rex, which are based on its muscle origin sites (scapula + coracoid). Unless you have evidence to suggest that Coracoid muscles in small-armed Theropod do not attach to its arms but to something else (like neck for example), otherwise what you said does not disprove anything about Carpenter’s interpretation for T-rex forelimb muscle actions.
Michael Habib (I posted above) does point out the coracoid in small-armed Theropod is for neck but not arm muscle attachments. However, the source is not published and it’s just to vague for any discussion. Based on the current muscle reconstruction, the Coracoid is still for arm muscles. So large Coracoid would mean strong protractor and adductor of the forelimbs.

I’ll see if I can find any. At any rate, that comparison, is again not really that relevant, you are comparing it to a vastly smaller animal, with proportionately vastly larger forelimbs. Stop for a second to imagine what carnivoran forelimbs would look like if they were as robust as large theropod forelimbs.
Theropod forelimbs are obviously way more robust than those of carnivorous mammals, but they are also way smaller relatively speaking.

Oh no, i did not suggest to you to find data on Carnivorans and compared them to Theropods. I just merely pointed it out for a sense of the sheer robusticity of Theropod forelimbs. You have to look for Theropod forelimbs data and compare them together, which is the only meaningful way to make comparison as you already said.

No, there aren’t any studies on megalosauroid forelimb biomechanics. Curious, considering how many there have been on the forelimbs of T. rex. There doesn’t seem to be a comparable research interest in them, despite the forelimbs clearly being more important for prey acquisition in these taxa.
But this is the humerus of the Baryonyx holotype (~2-3 t specimen?) compared to the humerus of sue (8t+ specimen) at equal length, and their actual relative sizes:

What's the point of that comparison anyway? Spinosaurids's humeri are ridiculously robust, more so than any Allosauroid, possibly even more so than basal Megalosauroid. If your definition of 'poor' forelimbs are anything that are less robust than Spinosaurids, then you may just as well include pretty much all carnivorous Theropod taxa in that 'poor' category. Allosauroidea would also look poor next to Spinosaurid.
Yes, it's quite frustrating that Spinosaurid's forelimbs are very under-studied. It seems like we're missing something when trying to infer predatory capacity of these guys. Most of the times, researchers only look at their skulls and teeth and pointed out that they eat small fish preys. However, somehow everyone forget that they also have massive forelimbs and claws that can make short works of medium-sized animals.

"The humerus is slender, and the deltopectoral crest is weakly developed in all tyrannosauroids except Eotyrannus (fig. 5.15)." "The olecranon process is moderately well-developed but short (fig. 5.16)."
From Holtz 2004, p. 123.

This part is a bit vague and generic tbh. Like it's really just one statement, no clear analysis whatsoever. But anyway, regarding deltopectoral crest:
Christiansen, p. 249, Encyclopedia of Dinosaurs

In ornithomimids
and tyrannosaurids, except Tyrannosaurus rex, the deltopectoral
crest was markedly reduced

Brochu (2003)

The humerus is expanded at both ends and bears a robust
deltopectoral crest. The shaft is cylindrical and becomes dorsoventrally
flattened as it approaches the head. The deltopectoral
crest is thick, rugose, and extends distally for one-third of
the length of the humerus. Prominent tuberosities are found
anterior and dorsal to the crest.

About, olecranon process, not sure about this one. I think Holtz is right when i look at the ulna bone myself. However, refer to what i post above:

Large tyrannosaurids, Torvosaurus, and Acrocanthosaurus occupy a region that is similar to that of large-prey-specialist cats, and are well separated from other theropods along the first two PC axes. Among both taxonomic groups, species occupying this region showed relatively short and robust forearms, as well as long olecranon processes, robust metacarpals, and large radial and metacarpal distal articular surface areas.

Also, isn't olecranon process related to triceps muscles? I can see triceps playing a stabilising role for when Theropod hold on to its preys but i can't see it plays a significant role when it comes to grasping and pulling they prey towards the Carnivores.

What's with the 'gracile' assessments (gracile humerus, gracile antebrachii?) that you keep repeating yourself? Where are those even from? What's the data to back up the assessments? Did you even read what i and Infinity posted above regarding T.rex forelimbs robusticity? Again please refer to Infinity's post (1, 2). Carpenter has even stated that Allosaurus's forelimbs are not as robust as those of T.rex. The measurements (midshaft tranverse diameter/bone length) also do not suggest that T-rex's forelimbs are not robust (i'll post about it later).

T. rex’ forelimbs seem poorly adapted for raptorial purposes compared to most other theropods. This is due to a combination of their small size relative to body size and a general trend of reduction within the forelimb (less expansive attachment areas on the humerus, comparatively gracile forearm, didactyl, thereby gracile manus). For its body size, T. rex forelimbs are just not as well-adapted for use in predation as those of Deinonychus, or Allosaurus, or Torvosaurus or Acrocanthosaurus, to name but a few examples.
All of these are animals that we can expect used their arms in an at least somewhat significant role. Because they are much larger for a given body size and/or have morphological adaptations far more optimized for raptorial purposes, as I have outlined before (larger claws, more strongly developed hands, larger reach, larger muscle insertions on the forelimb). Since it is usually other theropods we are comparing T. rex to, yes, it is accurate to say that T. rex forelimbs were poorly suited for raptorial purposes compared to these taxa
When you look at the hands of the T. rex and the Allosaurus in my comparison above, which one do you think can hold the larger load? Right, the Allosaurus, more fingers, more powerful antebrachium, larger claws. Now consider that the T. rex in question is 4 times larger, and would likely have to deal with far larger forces from its prey (or its own body mass) if it used its forelimbs in predation.
I tend to be quite meticulous about avoiding vague statements. I’m sorry if this one turned out to be too vague for your taste, but that was not due to lack of evidence, but because I thought it was fairly obvious. You had already quoted the comparison I made a few years ago, which clearly illustrated that, after all.

Again, if you have data to back up your assessments about robusticity, muscle attachments, etc and why you think T.rex forelimb 'grabbling' is an outrageous idea, please post it. Just don't make generic statements with a bunch of adjectives (larger, stronger, blah blah) without any substances. For example, you can make it more detailed by doing this. You look at the measurements of their forelimbs and you conclude that T.rex forelimbs are too thin. Or you can point out T.rex's certain forelimb muscle insertions (biceps, triceps, you name it) are far too underdeveloped based on some certain sources. Or you can point out that the robust scapula + coracoid are for neck muscle attachments and the arms are in fact much more lightly-muscles then what the published reconstructions suggest. Just back up your assessments with some data and perhaps try explain to why your assessment contradict Carpenter's regarding muscle origin from scapula + coracoid.

Also, why Deinonychus? Its forelimbs are clearly more gracile than those of T.rex, even in relative term. Again, i don't get what you meant by that

Your comparison is good for assessing the range of motions on different Theropod forelimbs but for robusticity assessment, it's not. It only shows you view from one side, the bones are probably not even situated completely parallel to the sagittal plane, which can cause skewed assessment. I'm sorry that your statements are still vague and generic.

I also thought it was clear I was comparing it in the context of other theropods actually well-adapted for this.

I think it should be clear that i'm not arguing that T.rex would use its forelimbs in a similar manner to other Theropods that you mentioned. Why would it? Its jaws, teeth, and neck muscle are perfectly adapted for holding on ('jaw grappling' if you will) to struggling preys. The forelimbs, if ever use, are clearly secondary to this and it would only act to add extra grips. The stress from struggling preys would be primarily on the jaws and neck, which are adapted for the job.
What i don't get is your definition of 'poor' forelimbs. T.rex's forelimbs are robust, even relative to its size, much more so than many smaller Theropod taxa. This suggests that T.rex forelimbs would have been able to withstand stresses from relatively (relative to its size) larger preys, then smaller Theropods taxa. It's not as adapted as Megalosauroid and Allosauroid, yes, but it's more adapted than small Theropods whose gracile forelimbs can only be used to catch really small, probably swallow-able preys.

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EDIT: I moved this to a separate post for easy future reference.

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Infinity Blade

Verdugo I sent an email to Ken Carpenter asking about the 2008 paper (and also the 199 kg bicep curl figure), just to be sure. We'll see if he can clear anything up, assuming he has the time to respond.

Yeah, that would be great.I personally suspect the 199 kg figure to be either bollocks or misinterpretation by the Wiki editor. For example, the editor may not realise the difference in Muscle force (without level arms) and Resistive force (with level arms).
I don't have a lot of problems with the 2008 one, just merely don't understand why they conclude that it's 'strong' when it's only able to culr 30-100 kg.

[theropod]

Posterior range of motion may be useful for pulling the preys back? Acrocanthosaurus has greater posterior range than Allosaurus as well, despite having similar anterior range.

But pull it back where? Inside its thorax? I don’t know what they had this large posterior range of motion for tbh (though maybe being able to be swept back that far, that could prevent the arms from getting caught on stuff and thereby damaged?), but I don’t see how it would be useful for predation.

I suppose that may cause interpretation and conclusion not entirely meaningful due to the large different humerus length across different Theropod taxa. He should have scaled the forelimbs based on the perimeter that is more related to size such as femur length or total hindlimb length. Regardless, it does not disprove strong protractor, adductor, and retractor actions of T-rex, which are based on its muscle origin sites (scapula + coracoid).

Yes, but it doesn’t disprove the shortcomings of the forelimb either.

Unless you have evidence to suggest that Coracoid muscles in small-armed Theropod do not attach to its arms but to something else (like neck for example), otherwise what you said does not disprove anything about Carpenter’s interpretation for T-rex forelimb muscle actions.

I did not say anything against his interpretations, I put them into the right context.

Michael Habib (I posted above) does point out the coracoid in small-armed Theropod is for neck but not arm muscle attachments. However, the source is not published and it’s just to vague for any discussion. Based on the current muscle reconstruction, the Coracoid is still for arm muscles. So large Coracoid would mean strong protractor and adductor of the forelimbs.

For the length of its humerus, T. rex has reasonably strong upper arm protractor and retractor musculature. Probably nothing special though when comparing it to another theropod of actually similar body (and relative scapulocoracoid) size.
Neck muscles also don’t really explain T. rex huge scapulocoracoid on their own. The sites for arm muscle attachment are still there, after all. The arm muscles don’t just turn into neck muscles.

Or rather, it does explain it, in explaining why even with small, not so important arms, the scapulocoracoids remain large, but it also doesn't mean the forelimb re- and protractors weren't correspondingly large, as there's no payoff here, they obviously have different insertions on the scapula.
There's probably a developmental linkage there, smaller proximal forelimb muscles would usually be linked to a smaller scapulocoracoid, which would adversely affect neck-muscle developent, which would therefore be negatively selected.

Oh no, i did not suggest to you to find data on Carnivorans and compared them to Theropods.

I meant data on theropod forelimb robusticity…
But I see you already did that.

What's the point of that comparison anyway?

To show what even the most robust T. rex humerus looks like next to the humerus of a way smaller baryonychine, both at unit length and in absolute terms (making comparison correcting for body mass pretty much superfluous, as this would only be even more extreme). Absolute terms are important. This is not just a question of how strong things are compared at the same humerus length (though I’ll wager in this case that the musculature actually on that forelimb in the Baryonyx would still be considerably bigger than the T. rex’ when scaled to the same length).

Which is why I think it’s clear that the latter’s forelimbs were much more raptorially capable (is that gramatically correct?) than the former’s. Besides the other factors, such as way larger claws, more massive distal limb elements etc.

Spinosaurids's humeri are ridiculously robust, more so than any Allosauroid, possibly even more so than basal Megalosauroid.

It seemed to me like you were asking for data on megalosauroid forelimb robusticity…

Yes, it's quite frustrating that Spinosaurid's forelimbs are very under-studied.

Pretty much all theropod forelimbs are understudied compared to T. rex, not just spinosauroid ones. There are what, at least three studies dealing in detail with the forelimb osteology and myology of T. rex, and some going so far as to make attempts at quantitative estimates of its strength? No other non-volant theropods have had that amount of attention devoted to their forelimb biomechanics. Which is weird considering ther likely play a much bigger role for them, although of course T. rex' forelimbs are puzzling from an evolutionary standpoint, making them worth studying.

This part is a bit vague and generic tbh. Like it's really just one statement, no clear analysis whatsoever. But anyway, regarding deltopectoral crest:

This part is vague because it is looking at it in the broader context of theropod osteology. Holtz also co-authored the chapter on basal tetanurans (if ever there was a vague category for theropods…) in the same volume. But as I said, this is certainly the case, I have my own eyes to look at theropod forelimb osteology. Check Acrocanthosaurus’ humerus:

acrohumerus (242.88 KB)

From Currie & Carpenter 2001

Also, isn't olecranon process related to triceps muscles? I can see triceps playing a stabilising role for when Theropod hold on to its preys but i can't see it plays a significant role when it comes to grasping and pulling they prey towards the Carnivores.

Extending the elbow is certainly relevant in pulling.

What's with the 'gracile' assessments (gracile humerus, gracile antebrachii?) that you keep repeating yourself?

I think self-explanatory. These bones are underdeveloped when compared to other theropods. Though I’ll admit "gracile" was the wrong word on my part as these bones aren’t actually particularly gracile, they are simply small. That still makes them weaker overall though. Scale a T. rex forelimb to even the same humerus length as that of another large theropod, as I did above, and you see what I mean. T. rex starts out really robust (in the shoulder girdle), then gets down to moderately robust, and decreases in as we move more distally. Other theropods have a really large, broad hand. That of T. rex is narrow (partly because of its reduction in digit count). That reduces how much force could be applied through it. Default assumption would be by a factor of about 2/3, as it really doesn’t look like the remaining digits in T. rex are becoming larger and stronger to compensate for that.

Where are those even from? What's the data to back up the assessments? Did you even read what i and Infinity posted above regarding T.rex forelimbs robusticity? Again please refer to Infinity's post (1, 2). Carpenter has even stated that Allosaurus's forelimbs are not as robust as those of T.rex.

Again, Allosaurus is an animal that’s usually 4 times smaller than T. rex. I wonder though how Saurophaganax’ humerus would stack up.

Also, why Deinonychus? Its forelimbs are clearly more gracile than those of T.rex, even in relative term. Again, i don't get what you meant by that

Because I knew this would come up. You’ve alluded to smaller theropods before. That’s the point. It’s forelimbs clearly are far more gracile. But that’s referring to unit length. Which is irrelevant, because they are way way larger for the size of the animal.

Your comparison is good for assessing the range of motions on different Theropod forelimbs but for robusticity assessment, it's not. It only shows you view from one side, the bones are probably not even situated completely parallel to the sagittal plane, which can cause skewed assessment. I'm sorry that your statements are still vague and generic.

I depicted them in parasagittal view. That’s a simplication compared to their real-life posture, but it’s close enough, and simplifies the comparisons.

I think it should be clear that i'm not arguing that T.rex would use its forelimbs in a similar manner to other Theropods that you mentioned. Why would it? Its jaws, teeth, and neck muscle are perfectly adapted for holding on ('jaw grappling' if you will) to struggling preys. The forelimbs, if ever use, are clearly secondary to this and it would only act to add extra grips.

Then what are we arguing about?

What i don't get is your definition of 'poor' forelimbs. T.rex's forelimbs are robust, even relative to its size, much more so than many smaller Theropod taxa.

they are robust relative to their size, i. e. Forelimb length, humerus length or whatever we scale them to, not its size,i. e. Femur length, or body mass. And yet you are certainly not trying to suggest T. rex’ forelimbs were as well-adapted for raptorial purposes as those of (for example) Deinonychus or do you? Sure, if you scale a T. rex forelimb isometrically to the length of a Deinonychus forelimb, it’s clear which is stronger. But that’s ignoring that they belong to two totally differently sized animals, and are completely different sizes relative to the sizes of those animals. A 70 kg Deinonychus’ forelimb would be way bigger, and likely also way stronger, than a hypothetical isometrically scaled 70 kg T. rex’ forelimb. Just like a T. rex forelimb sounds and looks very impressive next to a human forelimb (which are very roughly similar in length, though not robusticity), but not really the forelimb of a hypothetical isometrically scaled 8 ton human.

This suggests that T.rex forelimbs would have been able to withstand stresses from relatively (relative to its size) larger preys, then smaller Theropods taxa.

No, because you are again ignoring the crucial aspect that I highlighted in the beginning. Robusticity is relative to size. And also heavily allometric. It would be able to withstand stresses from prey items larger relative to the size of its arms. Big difference when comparing T. rex to smaller theropods.

It's not as adapted as Megalosauroid and Allosauroid, yes, but it's more adapted than small Theropods whose gracile forelimbs can only be used to catch really small, probably swallow-able preys.

Err something like Deinonychus would probably have been able to suspend its whole body mass (note that I’m not passing any judgement on whether it preyed on large animals or not, I’m just talking about mechanics here) from a prey item it latched onto on those forelimbs. Something T. rex clearly could not do. The original point was that similar to (though not to the same extreme) as abelisauroids, T. rex forelimbs are greatly reduced in size for the size of its scapulocoracoid.

So seemingly the forelimb was less developed, but the scapulocoracoid was retained. I’m also not arguing its forelimbs were functionless or anything like that, simply that for the size of that scapulocoracoid, there’s comparatively little going on in the forelimb department in both T. rex and Abelisauroids (not necessarily to the same degree, though purely from the robusticity angle relative to forelimb size, abelosauroid forelimbs are robust as well).

I totally agree with the conclusion of your post. Nice one, btw.

[Infinity Blade]

Yeah, that would be great.I personally suspect the 199 kg figure to be either bollocks or misinterpretation by the Wiki editor. For example, the editor may not realise the difference in Muscle force (without level arms) and Resistive force (with level arms).

I still trust that it's indeed a legitimate figure (but now that you mention your skepticism, it may just be mere faith on my part), but I wonder if the 2008 study is a refinement of the 2001 one.

[Verdugo]

theropod
Man, i hate to admit this but you're absolutely correct. I have done some calculations on T-rex's metacarpal to see it it really holds up, quantitatively (rather than just some generic qualitative assessment). Turns out it doesn't!. You're right, the metacarpal of T-rex is quite fragile (and appropriately gracile too). The humerus and antebrachii are actually fairly strong but the metacarpal is not. If we go with the principle that 'the chain is only as strong as its weakest link' then the metacarpal will be weak link and it will be most prone to failure. I'll post more about this later when i have more times. Either the 'slasher' theory holds up or otherwise, the forelimbs would have little use for raptorial purposes.

Any ideas of how to post excel tables in forum? My excel has become too much for screenshot (i have too zoom out too much to the point the numbers are no longer readable in screenshot)

[theropod]

You can copy and paste them using the code-tag, but the amount of space is limited as well

Looking forward to seeing your figures.

[Verdugo]

Forelimbs Robusticity and Bending Strength of Theropod taxa
Materials and Methodology
T.rex (Sue)'s forelimbs data from Brochu (2003). Allosaurus ('Antredemus') from Gilmore (1920). Acrocanthosaurus (Fran) from Currie & Carpenter (1999)

Humerus, radis, and ulna measurements will be used to calculate Robusticity and Bending Strength. Measurements are in mm

Robusticy = width (supposedly mediolateral width) at the mid shaft / bone length

The rationale for this is because the long bones are most thin at the midshaft and thus if it ever break, the midshaft will be the most probable place. Robusticity at midshaft had been used on Carnivorans as an assessment of the animal bone's resistive strength (Doyle, 2009; Meachen, 2009; Meachen, 2012)

Bending Strength = Section Modulus / Moment Arm Length

Following the principle established in Therrien (2005); Christiansen (2007a); Christiansen (2007b)

Section modulus is calculated at the midshaft. The assumption is that the midshaft will be a solid circle in cross section. Which is not correct as the actual midshaft would be more like hollow oval in cross section. However, i cannot find the data to follow the more accurate approach so some assumptions have to be made. Moment arm length will be half the bone length as the force applied is assumed at the distal-most section of the respective bones. Measurements in mm^2

Strength is only relevant in relative term as larger animals are indeed stronger. Strength will be adjusted based on estimated body mass.

Relative strength = Absolute Bending Strength / Body Mass^(2/3)

As Body mass increases at a faster rate then Strength, adjustments have to be made. Body mass of T.rex is 8500 kg; Allosaurus is 1500 kg; Acrocanthosaurus is 6000 kg.

The stress on the antebrachii would most likely spread between ulna and radius and not on each bone individually. Thus a sum of strength of ulna and radius, both in absolute and relative term will be calculated for interpretation of forearm (antebrachii) strength. A sum of all limb bone strength will be calculated for an overall strength assessment.
Result and Discussion

The larger Theropods (T.rex, Acro) in this case are both more robust than the smaller one (Allo). However, Robusticity may not be good indicator for Strength especially on animals with different limb length such as this case. As Strength grows at the 2nd power, a larger bone will be stronger than a smaller one even though its robusticity is similar. Thus Bending Strength is a more meaningful measurement for interpretation purposes.

Humeus: In absolute term, obviously, the larger Theropod have much stronger humerus. T.rex and Acro score similar in this regard, thus it suggest similar resistive strength in absolute term. For example, if Acro's humerus is strong enough to withstand the force of a 6000 kg struggling prey then T.rex's humerus should be able to withstand similar force. When adjusted for weight, both Allosauroid score higher than T.rex does, suggesting stronger humerus relative strength (albeit not significantly so, about 25% stronger)

Radidus: In absolute term, Acro's strength scores the highest, then T.rex, then Allo. In relative term, Allo and T.rex are similar in strength while Acro is significantly stronger than the others.

Ulna: In absolute term, T.rex's strength scores the highest, then Acro, then Allo. In relative term, T.rex scores only slightly higher than Acro. Both larger Theropods score significantly higher than the smaller one, even in relative term.

Antebrachii (forearms): In absolute term, Acro scores highest in strength, follow closely by T.rex and then Allo.
The trend in relative term is quite interesting. In relative term, the antebrachii of T.rex is significantly stronger than that of Allo (about 40% stronger). This is due to the fact that T.rex has significantly stronger ulna than Allo even though the radius is similar in strength. As expected, Acro is stronger than both in this aspect (about 30% stronger than T.rex).

Total forelimbs: In absolute term, Acro and T.rex scores similar to each other which suggests similar forelimbs resistive strength. This means that T.rex and Acro's forelimbs should be able to resist force from struggling preys of the same size. Obviously, in absolute term, both larger animals are so much stronger than the smaller one.
In relative term, T.rex and Allo scores similar in this regard. Allo has stronger relative humerus than T.rex but T.rex has stronger antebrachii than Allosaurus so the total forelimb strength is similar. At first glance, this seems to suggest proportionally similar prey restraining capabilities of the forelimbs due to having proportionally similar forelimb strength. For instance, if a 2 tonne Allo can restrain a 1 tonne struggling prey then a 8 tonne should be able to restrain a 4 tonne prey.

However, there are issues with this interpretation. Terrestrial animals muscle force (hence Strength) probably increases at positive allometry in response to increase in size (Arthur et al, 2015). The reason for this is because mass increase at a much faster rate than Strength does (assuming isometry). If the muscle force of terrestrial animals only increases at isometry, they will not be strong enough to move themselves at larger size. This means that the force of struggling prey animals probably also increase at positive allometry too. On the other hand, T-rex's forelimbs only increases at isometry when compared to Allosaurus. This suggests that the prey-predator mass ratio of T-rex's forelimbs will be less than that of Allosaurus despite not having weaker forelimbs proportionally. So if a 2 tonne Allo can restrain a 1 tonne prey, an 8 tonne T-rex can only restrain preys that weigh less than 4 tonnes.

Acro scores higher than both in relative term, having the strongest humerus and antebrachii. Thus, it should be adapted for restraining rather large preys. Acro increase at positive allometry to Allo. This means that Acro probably can maintain similar prey/predator mass ratio as Allo or possibly achieve even higher ratio than Allo.
Conclusion: Relative to its size, T.rex forelimbs are as strong as those of Allosaurus. However, due to its larger size, its forelimbs may be proportionally weaker compared to its preys. Thus this suggests that T.rex forelimbs would only be capable of restraining smaller prey/predator mass ratio than Allo would. Acro's forelimbs scale in positive allometry to Allo. This suggests that Acro can either maintain similar prey/predator mass ratio or possibly achieve a higher ratio than Allo (big game adaptions?)
Limitations: Assumption that the bone is solid circle in cross section may be inappropriate. One specimen per species may be too low and may not account for the varied morphology across specimens. Analysis is quite sensitive to Body mass and the body mass assigned here may be inappropriate. Need to collect more data on other Theropods such as Deinonychus and Torvosaurus for wider cross-species comparison.

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Comprehensive Forelimbs Comparison and Implication: T-rex vs Allosaurus
Introduction
In my previous quantitative comparison between T-rex and 2 Allosauroid based on several principal forelimb bones, which are Humerus, Radius, and Ulna. I concluded that proportionally speaking, T-rex's forelimbs are as strong as those of Allosaurus, which is impressive considering T-rex has visually quite reduced forelimbs compared to Allo (however, it is still only able to restrain proportionally smaller preys due to scaling of prey size). In absolute terms, T-rex forelimbs are as strong as those of Acrocanthosaurus. This means that while T-rex forelimbs are not as strong as those of Allosauroid relative to its massive size (Sue the T-rex is one of the largest Theropod ever found), it should still be strong enough in absolute term to serve as a secondary tool to help T-rex increase its grip on its prey in addition to its already impressive jaw. My first post quantitatively supported the hypothesis of the usage of forelimbs for raptorial purposes.

However, other members (theropod ) pointed out some issues. T-rex has visually tapered forelimbs. The limb starts out at really robust at the scapulacoracoid, and it gets increasing less so till it gets to the metacarpal and the phalanges where it appears quite slim and fragile. And it also does not help that T-rex only has 2 metacarpal bones to distribute stress in comparison to Allosauroid who have 3 bones for the same job. He concerns that the distal limb segments of T-rex may not be strong enough and thus it may be a bottleneck to prey-grappling hypothesis. Thus, i will quantitatively compare the Bending Strength between T-rex's metacarpal and Allosaurus's metacarpal to see if the prey-grappling theory of T-rex forelimbs still holds up.
Material and Methodology
The materials are from the same sources and from the same specimens that i cited above, nothing really changes. The reason Acrocanthosaurus is not included in this post is because i cannot find the required materials for it to compute figures.
Methodology stays the same, Bending Strength will be assessed at the mid shaft of each metacarpal bones. The applied force is assume to be at the distal-most part of the metacarpal and thus the Moment arm length will be half of the shaft. After that, i will sum the Strength of each metacarpal bones to get the overall metacarpal Strength (the strength of the 'paw' if you will).
Result and Discussion

Only metacarpal figures will be included here because i already discussed other forelimb bones above (the excel file will have all the figures). I included Robusticity figures here. However, i already pointed out above that comparing Robusticity in this context may not be meaningful. Thus, there will be no assessments based on the Robusticity figures.

Metacarpal 1: In absolute term, the result of M1 is surprising. The M1 of Allosaurus is actually significantly stronger in absolute term!. This is unexpected due to the large size differences between two animals. The Allo size here is uncertain but i think it's unlikely that it can weigh above 2000 kg. On the other hand, Sue the T-rex can easily be estimated to weigh over 8000 kg. At bare minimum, the T-rex here is 4x the size of Allo, yet its M1 is nowhere near as strong. Needless to say, T-rex M1 is much weaker in relative term as well.

Metacarpal 2: In absolute term, as expected, the much larger T-rex also has much stronger M2. In relative term, T-rex's M2 is still stronger, albeit insignificantly so. This suggests that T-rex M2 is as strong as that of an isometrically scaled-up Allo. As we already discussed above, this also means lesser prey-predators mass ratio due to positive allometry scaling of preys' Strength.

Metacarpal 3: Well, Allo's M3 is the weakest in both absolute and relative term when compared to M1 and M2. But i guess it's still better than nothing. T-rex M3 is not included because there is no data for it. Also, i can't see it plays any roles in stress dispersion.

Total metacarpal: The result in absolute term is unexpected. T-rex's metacarpal is only as strong as that of Allosaurus, despite being 4x more massive. In relative term, needless to say, Allo is significantly stronger. This confirms the bottleneck concern. T-rex's humerus and antebrachii are similar in strength to that of Acrocanthosaurus, however its metacarpal is not in anyway stronger than that of a much smaller Allosauroid. The weak metacarpal here will constrain the entire forelimb raptorial capacity ('a chain is only as strong as its weakest link' principle). If one assume that Allo's forelimbs are adapted to restrain preys similar to its body mass (about 1500 kg) then that should be the maximum amount T-rex can restrain too. If T-rex tries to restrain larger preys with its forelimbs, its metacarpal will just come off.

Total forelimb: The T-rex's forelimbs are still stronger in absolute term overall (due to having stronger humerus and antebrachii in absolute). However, i don't think that has any relevance here because T-rex forelimb is already constrained at its metacarpal (as its metacarpal is not in anyway stronger than that of Allosaurus).
Conclusion:
With a metacarpal only as strong as an animal significantly smaller than T-rex is, i think we can safely conclude that T-rex's forelimbs are not adapted for restraining preys. This assessment is also consistent with qualitative one. T-rex's deltopectoral crest is not very well developed when compared to Allosauroid. The area at the olecranon process for muscle insertion is smaller than that of Allosauroid. The distal width of the humerus is very narrow, suggesting underdeveloped epicondyle (from what i have seen about Carnivoran anatomy, epicondyle is related to wrist stabilising muscles, but i don't know if the same principle can be applied here; Meachen, 2009; Meachen, 2012).
There is a 'forelimb slashing' hypothesis around but we have to wait for the published paper to come out to assess if it can hold any water. However, i think we can safely disprove the 'large game, Felids forelimb grappling' hypothesis for T-rex.
Criticism:
Some may argue that Allosaurus's metacarpal is simply overbuilt compared to the rest of its forelimb bones. This is because the metacarpal Strength value is significantly higher than that of other bones as in the table i posted. However, i don't think this is the case. My assessment is based on using the Bending Strength of metacarpal at the mid shaft. However, because the metacarpal are such short bones, it's very difficult for something so short to break under Bending Stress. In reality, the metacarpal is more likely to break under shear stress if it ever to break at the mid shaft. However, there are several joints in the metacarpal section that are much more prone to stress than the bone itself. For instance, the joint between carpal and metacarpal (which i assume is probably cartilage) can be prone to tensile stress due to it being made out of less resistive materials. Heck, that cartilage joint is certainly more prone to break under Bending Stress and shear stress than the bone shaft itself. Long story short, it's very daunting and unnecessary (not to mention, such data are not available) to try accurately comparing each limb sections of an animal relative to each other in Strength. However, for cross-species comparison, it's still meaningful. If T-rex's metacarpal is comparable to that of Allo under Bending Stress at the mid shaft, then one could also reasonably expected its comparable in strength to Allo when under other more relevant metacarpal-breaking stress as well.

For the record, the metacarpal value of T-rex is also higher than those of its robust humerus and antebrachii. There is no reason to believe that the puny-looking metacarpal of T-rex is 'overbuilt' compared to its clearly more massive limb elements. Thus, the 'overbuilt' argument does not hold any water.
Final Verdict:


Well, perhaps Rex should have stuck to the thing he does best


P/S: Most exhausting post i ever made on this forum

Attachments:

Theropod Forelimb.xlsx (17.42 KB)

[Infinity Blade]

theropod
Verdugo

I posted some documentation of alleged pathologies (in tyrannosaurids) caused by conspecific manual unguals (this is Rothschild (2013) btw, the same paper with evidence suggesting tyrannosaurid foot claws were weapons, of which I am firmly convinced), but I deleted the post because I wasn't too confident in it. Do you guys want me to repost it and tell me what you think?

[Infinity Blade]

I'll take theropod's like as a yes. Taken from Rothschild (2013).

[creature386]

What was the reason for your lack of confidence, if I may ask? Even factually wrong sources can spring informative discussion.