Theropod non-locomotory limb function

[theropod]

At forelimb lenght parity or at overall size parity?

It appears that carnosaur and megalosaur forelimbs are considerably more robust than those of carnivorans, but that’s because they are so relatively short for the most part (i.e. their size reduction was primarily in shaft lenght). They also show huge muscle attachment sites.

[Infinity Blade]

Overall size parity (wouldn't it be rather obvious at forelimb length parity?).

[theropod]

That’s difficult to say.

Large-armed forms (basal megalosauroids, basal carnosaurs neovenatorids or spinosaurids) could be able to match the carnivorans, but my guess is that the forelimbs of most derived carnosaurs, despite being very powerfully built, would be just too small to make up for it.

Bipedalism is a two edged sword. It relieves the forelimbs of the necessity of being used for locomotion, so their movement range and muscle pattern does not have to adapt for that (reduced flexibility comes at the benefit of greater strenght, so if unnecessary movement ranges are given up that allows to increase resistance and moment arms in those that remain). On the other hand, this usually favours the forelimbs to be reduced in size as the animals grow larger.

[creature386]

The forelimb function of ornithomimosaurs may deserve a mention, since their arms were long, but probably had a non-raptorial function. I quoted The Dinosauria on Struthiomimus in the Struthiomimus vs moa thread on carnivora. Here the whole text about ornithomimosaur forelimbs from that book (basically just one extra sentence):

The nonraptorial nature of the forelimb has also generated much discussion of ornithomimosaur life habits. Although proportionally long, the ornithomimosaur forelimb is weakly developed in all taxa, and the unguals are either weakly curved or straight, arguing against a predatory role. Nicholls and Rusell (1981) undertook a functional analysis of the forelimb of Struthomimus and concluded that there was little potential for pronation and supination of the antebrachium; however, they interpreted an extension of the forelimb and suggested that it may have been used for grasping branches and fern fronds. Other ornithomimids, such as Gallimimus bullatus, have shorter hands than Struthiomimus altus and may not have been able to perform the same range of manual movements (Barsbold and Osmólska 1990)

Page 149

[Infinity Blade]

Sort of relevant.

I read the first page of the Carnivora variant of this thread again and I was particularly focusing on the importance of Tyrannosaurus' forelimbs in predation, and it was noted that T.rex had a proportionately large coracoid (but also comparatively thin, elongated scapulae). Could the coracoid and scapulae muscles rather have aided the neck musculature and help it grapple with the mouth better (I expect the coracoid muscles to help a lot, but not so much the scapulae muscles)?

[creature386]

I am not sure about this. I know that the coracoid is connected to the biceps and such, but I am not sure if it is connected to the neck muscles. Given that it may be large in overall dimensions, but very short, I doubt that it was connected to arm and neck muscles.

[theropod]

Sept 5, 2014 7:46:18 GMT 5 Godzillasaurus said:

Well having a short tail only means something when comparing it to another animal with a proportionally longer tail at length parity (like velociraptor), in which case the latter's longer tail will make it "more gracile" by the virtue of proportions alone. That doesn't make the creature's entire body any more or less robust. I have never heard of the raptorial claw idea for oviraptorids; not only did they lack the specialized and enlarged second claw of dromeosaurids which were used most likely for killing, but it would have also been almost completely unnecessary given the fact that they were only suited for feeding on small animals and probably vegetation as well. A macrophagous killing characteristic like what we find in creatures with recurved, serrated teeth such as velociraptor would be unnecessary for an animal that was ill-suited for feeding on larger dinosaurs. Unless of course that claw could be used for defense, but its speed and agility would have likely been its primary defense mechanism if I may say so myself.

And for your second paragraph, that still doesn't really make it a valid theory. Many derived theropods evolved large, powerful jaws and longish teeth (for varying purposes among different groups albeit, but still it is the same principle) as an adaptation for killing other vertebrates. Generally, save for spinosaurids (which would have used their forearms for grasping fish if not for tearing apart anything), predatory theropods with greater emphasis on jaw and tooth function also possessed very short and almost completely useless forearms.

I must admit that I am on the edge about dromeosaurids; they did not possess the largest or strongest jaws but as well possessed long and prominent forelimbs. One might agree that they could have been used for grappling, but I am not so sure about that. They were shaped like bird wings (obvious evolutionary connection is obvious!): being long and having the wrists motioned backwards. This does not seem like the ideal shape for grasping at all, especially when it has actually been theorized that the hind limbs had that function (as apparently the enlarged second claw was actually ill-suited for tearing but was instead terrific at hooking): royalsocietypublishing.org/content/2/1/110

So unless dromeosaurids had capabilities for large wrist movement, I definitely concur that their hind limbs would be used for securing pray. The forearms might provide a tad bit of grabbing support, but not enough to be considered significant grasping weapons

I’ll try to track down where I read it. Anyway, the "Citipati sp." skeletal from this post→ should make clear what I mean, both in terms of raptorial forelimb claws and robust built.
Oviraptorosaurs actually have fairly compact bodies too (as I already wrote!). The only thing that’s gracile about them is the neck and the legs.

I’m not sure why you seem to assume they would just flee from imminent danger all the time. Many oviraptorosaurs were large compared to potential predators, and while fleeing with those cursorial legs might have been an option, fighting using the powerful beak and claws would be too.

Your second paragraph seems pointless. Having useless forelimbs automatically creates greater emphasis on the jaw and tooth function because there’s less to distract from them/be used instead, just like everyone else being less than 150cm tall would automatically make me the tallest human on earth without me actually changing height. I did not propose any theory (Please look up what the term→ means!), for it to be a theory it would require repeated confirmation through empirical evidence. That theropods sometimes used their forelimbs to kill is a hypothesis that has been proposed at times, and it is misplaced to rule it out and call it BS when it is very well possible. Usage of the jaws is merely a more likely alternative in almost all theropods, but usage of the forelimbs seems possible in many.

Where do you take that "wrists motioned backwards" stuff from? That dromaeosaurids were capable of a degree of ulnar abduction (Carpenter 2002) does not mean that was how they held their hands all the time. I think this degree of motion is rather helpful for manual dexterity than the reverse. And that they are long is a major advantage for grappling.
The function of the pedal ungual II of dromaeosaurs has been debated back and forth, remarkably without any valid testing done so far or any attempt of finding out the shape of the keratin sheath by means of comparative anatomy and extant analogies. As a mere gripping tool, I think the extreme size of this claw does not make sense. As a tool for slashing, I’m not sure whether relatively light animals could really generate the forces necessary (although heavier ones like utahraptor have better prerequisites here). I think it was primarily a stabbing weapon.
How do you think this precludes the use of the hand claws for grasping?

[Godzillasaurus]

Sorry for the long post previously; I was trying to say something so simple but it came off as 4 whole paragraphs

I’ll try to track down where I read it. Anyway, the "Citipati sp." skeletal from this post→ should make clear what I mean, both in terms of raptorial forelimb claws and robust built.
Oviraptorosaurs actually have fairly compact bodies too (as I already wrote!). The only thing that’s gracile about them is the neck and the legs.

For one, there wasn't that great a difference in both skeletals. So I don't see why that should matter at all.

And second, being compact does not always make something robust. For example, titanosaurs are considered to be notably thick-bodied sauropods with reasonably long tails (although nothing too special like in diplodocus), but does that make them more gracile than a much weaker-built creature with a shorter tail? Not really.

I’m not sure why you seem to assume they would just flee from imminent danger all the time. Many oviraptorosaurs were large compared to potential predators, and while fleeing with those cursorial legs might have been an option, fighting using the powerful beak and claws would be too.

Many? Only gigantoraptor comes to mind there, unless there is a whole slew of new large genera that I am unaware about.

That theropods sometimes used their forelimbs to kill is a hypothesis that has been proposed at times, and it is misplaced to rule it out and call it BS when it is very well possible. Usage of the jaws is merely a more likely alternative in almost all theropods, but usage of the forelimbs seems possible in many.

But the forearms are not designed to kill, whereas the jaws in the majority of large-skulled theropods are clearly structured to slash at flesh and tear chunks off. Using such infinitesimal forearms to kill (which I have yet to see in large-jawed theropods aside from spinosaurids and I believe some megalosaurids as well) is a baseless idea. Just because the claws are sharp and hooked does not make the entire forearm a useful killing tool, especially when you consider how the jaws of many theropods were enlarged for likely the very purpose of killing.

Where do you take that "wrists motioned backwards" stuff from? That dromaeosaurids were capable of a degree of ulnar abduction (Carpenter 2002) does not mean that was how they held their hands all the time. I think this degree of motion is rather helpful for manual dexterity than the reverse. And that they are long is a major advantage for grappling.

As I said, this could very well be an evolutionary thing. It seems that only coelurosaurs like dromeosaurids among a few other groups were oftentimes holding their forearms in that position. This is a clear link between the typical smallish theropod forearm to the wing of a bird:



And with this said, there just may be a disadvantage to this kind of positioning despite the limb length in terms of how it is used in predation.

The function of the pedal ungual II of dromaeosaurs has been debated back and forth, remarkably without any valid testing done so far or any attempt of finding out the shape of the keratin sheath by means of comparative anatomy and extant analogies. As a mere gripping tool, I think the extreme size of this claw does not make sense. As a tool for slashing, I’m not sure whether relatively light animals could really generate the forces necessary (although heavier ones like utahraptor have better prerequisites here.

I too used to find the size a "clear" indicator of a slashing function; I mean as long as it was narrow enough it could have definitely been used as such. But also, I do not really support this "insufficient force" hypothesis. Note that, as a dromeosaurid gets larger, and the proportions remain consistent, its claws will too. So thus, a small animal is not going to need extensive force to drive a claw that is proportional, if that makes sense. It is about proportions, not necessarily overall size.

I think it was primarily a stabbing weapon.

Sure, it was definitely enlarged. But I have trouble with this idea. Attacking something so large with a hook-like weapon would not be a sufficient stabbing tool, or at least if it was actually trying to gravely wound the prey. Specially-designed stabbing weapons in animals are usually straightened and elongated for the most part (spike-like), not recurved and hook-like.

How do you think this precludes the use of the hand claws for grasping?

Well unless we can find conclusive evidence that the positioning of the hands and angle of the wrists was not disadvantageous, I am unsure. For all we know, they could have been used in social activities through the presence of colorful plumage.

[theropod]

For one, there wasn't that great a difference in both skeletals. So I don't see why that should matter at all.

I didn’t say it did. However, this is by far the more complete specimen, so it makes way more sense to use it as a basis for any observation.

And second, being compact does not always make something robust. For example, titanosaurs are considered to be notably thick-bodied sauropods with reasonably long tails (although nothing too special like in diplodocus), but does that make them more gracile than a much weaker-built creature with a shorter tail? Not really.

You are talking about the terms compact and robust, and then you try to explain the difference between them without using either. That does not work.

For our intends and purposes, oviraptorids are relatively robust in built, by means of their compact built (in most cases these are interchangeable, even though robust has different, mechanical implications while compact just refers to the shape). What they definitely aren’t is gracile.

Many? Only gigantoraptor comes to mind there, unless there is a whole slew of new large genera that I am unaware about.

Gigantoraptor erlianensis is gigantic. Anzu wyliei, Citipati osmolskae, Chirostenotes pergracilis are all fairly large. At least a lot larger than small albeit macropredaceous dromaeosaurs like Velociraptor, or Saurornitholestes, or Tsaagan (there are likely more oviraptorosaurs that outsize those).

But the forearms are not designed to kill, whereas the jaws in the majority of large-skulled theropods are clearly structured to slash at flesh and tear chunks off.

So what? I already responded to that!

Using such infinitesimal forearms to kill (which I have yet to see in large-jawed theropods aside from spinosaurids and I believe some megalosaurids as well) is a baseless idea.

What do you yet have to see? Infinitesimal forearms? The animals you list have very well-developed forearms, among the most massive in theropoda (did I not tell the story how when I first looked at the osteological description of B. walkeri I mistook its ulna for a humerus?).
The best example of an infinitesimal forearm is Carnotaurus, it’s entire antebrachium is litterally just the size of its palm. I’m not suggesting theropods with tiny forearms that lacked the capability to do any serious damage to have used them for killing. I am talking about those which have robust, well-developed forearms and manus, Acrocanthosaurus for example, Torvosaurus, Allosaurus, Baryonyx…
I hope I won’t have to repeat myself again: I’m not saying they evolved for this purpose, I’m saying that it’s not impossible that it happened, just like it’s not impossible for a goat to climb a tree, or for a crocodile to disembowel a zebra (just less extreme).

Just because the claws are sharp and hooked does not make the entire forearm a useful killing tool, especially when you consider how the jaws of many theropods were enlarged for likely the very purpose of killing.

I litterally wrote that exact thing!

As I said, this could very well be an evolutionary thing. It seems that only coelurosaurs like dromeosaurids among a few other groups were oftentimes holding their forearms in that position.

That’s utter hogwash, not all coelurosaurs were even capable of this motion. Coelurus for example has a tiny ark of ulnar/radial motion of the wrist, Allosaurus has considerably more, albeit not as much as Deinonychus.

This is a clear link between the typical smallish theropod forearm to the wing of a bird:

It seems you are confusing elongation of the phalanges (which is likely related to size to a fair degree) with the manual range of motion.

And with this said, there just may be a disadvantage to this kind of positioning despite the limb length in terms of how it is used in predation.

what "kind of positioning"? There is no fixed posture here, Dromaeosaurs could hold their forelimbs the same way every other theropod could if they wanted to. They had an increased range of ulnoradial motion of the wrist, not a reduced one. I.e., they are perfectly capable of assuming the same posture with the carpals and antebrachium aligned in one line, but they can also abduct it somewhat.

I too used to find the size a "clear" indicator of a slashing function; I mean as long as it was narrow enough it could have definitely been used as such.

"Too" implies that someone else does. Who are you referring to, Ostrom? Kirkland and colleagues? …?

But also, I do not really support this "insufficient force" hypothesis. Note that, as a dromeosaurid gets larger, and the proportions remain consistent, its claws will too. So thus, a small animal is not going to need extensive force to drive a claw that is proportional, if that makes sense. It is about proportions, not necessarily overall size.

It actually does not make sense. The force the animal can excert with its claw is limited by its weight, because the direction in which the claw will be motioned during attacks will be downward in most cases. And its weight grows cubically, while the surface of the claw’s edge only grows quadratically, i.e. a bigger dromaeosaur will be capable of generating greater pressure, and is thus more suited for slicing through something. There’s an obvious difference between a 15kg Velociraptor and a 500kg Utahraptor in terms of limitations imposed by body weight.
Please have a look at Carpenter (1998) on this matter.

I realize opinions are conflicting on this matter (Ostrom 1969 and Kirkland et al.1993). But the source you posted also argues that it’s unlikely the claw could slice, at least in Velociraptor. You are contradicting what you wrote earlier, that the hindlimbs also fulfilled a grasping function.
We definitely cannot assert that dromaeosaur claws were capable of slicing, at least not in smaller species, and they likely wouldn’t have to in order to be effective weapons.

Sure, it was definitely enlarged. But I have trouble with this idea. Attacking something so large with a hook-like weapon would not be a sufficient stabbing tool, or at least if it was actually trying to gravely wound the prey. Specially-designed stabbing weapons in animals are usually straightened and elongated for the most part (spike-like), not recurved and hook-like.

And which weapons would that be for example?

Raptorial claws are almost always strongly curved, including those of birds of prey, which are used for stabbing. A curved shape helps the claw to stab AND hook. Furthermore, if the animal rotates its toe to puncture something with the claw, a curved claw’s tip will be pointing in the right direction, that of a straight one not. Using a straighter claw would require a major alteration in the way it uses it (pushing along the axis of the toe), and therefore in its foot morphology. This is probably not practical for an animal that uses its feet to both restrain and effectively kill prey as well as walk, because these require a degree of dexterity you won’t find in a highly cursorial animal that may be well adapted for jabbing its foot forward (like a cassowary). The claws found in accipitriforms are obviously a better analogy.

Also, attacking something HOW large? What are you talking about?

---

References:
Carpenter 1998: www.arca.museus.ul.pt/ArcaSite/obj/gaia/MNHNL-0000778-MG-DOC-web.PDF
Kirkland et al. 1993: www.academia.edu/225747/A_large_dromaeosaurid_Theropoda_from_the_Lower_Cretaceous_of_Eastern_Utah
Ostrom 1969: peabody.yale.edu/sites/default/files/documents/scientific-publications/ypmB30_1969.pdf

[Godzillasaurus]

You are talking about the terms compact and robust, and then you try to explain the difference between them without using either. That does not work.

Compact means that something is restricted in dimensions in size, like a compact car. That does not make an animal more robust if their tail is simply shorter in proportion.

Gigantoraptor erlianensis is gigantic. Anzu wyliei, Citipati osmolskae, Chirostenotes pergracilis are all fairly large. At least a lot larger than small albeit macropredaceous dromaeosaurs like Velociraptor, or Saurornitholestes, or Tsaagan (there are likely more oviraptorosaurs that outsize those).

Fair enough, but does this outnumber the amount of small oviraptorosaurs?

What do you yet have to see? Infinitesimal forearms? The animals you list have very well-developed forearms, among the most massive in theropoda (did I not tell the story how when I first looked at the osteological description of B. walkeri I mistook its ulna for a humerus?).
The best example of an infinitesimal forearm is Carnotaurus, it’s entire antebrachium is litterally just the size of its palm. I’m not suggesting theropods with tiny forearms that lacked the capability to do any serious damage to have used them for killing. I am talking about those which have robust, well-developed forearms and manus, Acrocanthosaurus for example, Torvosaurus, Allosaurus, Baryonyx…

Being present in more derived animals does not automatically make something "larger"; carnotaurus was rather primitive, yes, but allosaurs too possessed rather small forearms along with most other theropods which used their jaws as the primary means of hunting. Spinosaurids are an exception, but yet their arms were still not tremendously large.

That’s utter hogwash, not all coelurosaurs were even capable of this motion. Coelurus for example has a tiny ark of ulnar/radial motion of the wrist, Allosaurus has considerably more, albeit not as much as Deinonychus.

Allosaurus was not a coelurosaur...

And maybe I should make my point more clear. It is not that "most coelurosaurs held their forearms like that as a "resting position", but that it appears to be a trait that was developed in more advanced groups closely related to aves.

It seems you are confusing elongation of the phalanges (which is likely related to size to a fair degree) with the manual range of motion.

It was supposed to represent a link between non-avian dinosaurs and avian dinosaurs; the more bird-like hand morphology and positioning seems to be much more well developed in related coelurosaurs.

what "kind of positioning"? There is no fixed posture here, Dromaeosaurs could hold their forelimbs the same way every other theropod could if they wanted to. They had an increased range of ulnoradial motion of the wrist, not a reduced one. I.e., they are perfectly capable of assuming the same posture with the carpals and antebrachium aligned in one line, but they can also abduct it somewhat.

Can I have a paper for this? This is something that needs supportive evidence.

And besides, does that necessarily make them useful grasping tools? Think about the purpose of the hind legs and second claws again. The claws of theropods would have probably only provided support in grasping, as the hands were still quite primitive and unspecialized compared to those of animals specifically designed to grasp like primates. When attacking large prey for any theropod, I do not think the forearms would provide very valuable "hooking" given their morphology and reduced movement/inferior positioning overall compared to many mammals. Heck, even rodents and a few carnivoran groups can grasp things effectively.

"Too" implies that someone else does. Who are you referring to, Ostrom? Kirkland and colleagues? …?

You : "As a mere gripping tool, I think the extreme size of this claw does not make sense"

It actually does not make sense. The force the animal can excert with its claw is limited by its weight, because the direction in which the claw will be motioned during attacks will be downward in most cases. And its weight grows cubically, while the surface of the claw’s edge only grows quadratically, i.e. a bigger dromaeosaur will be capable of generating greater pressure, and is thus more suited for slicing through something. There’s an obvious difference between a 15kg Velociraptor and a 500kg Utahraptor in terms of limitations imposed by body weight.

Hmm, well what about the relationship between the animal's body size and the respective claw size? As I said, it is of course going to be easier for Utahraptor to drive its own claw down into the hide of a prey animal than deinonychus or velociraptor, that is a given because of its much larger size. Can you quote where the paper talked about this?

I realize opinions are conflicting on this matter (Ostrom 1969 and Kirkland et al.1993). But the source you posted also argues that it’s unlikely the claw could slice, at least in Velociraptor. You are contradicting what you wrote earlier, that the hindlimbs also fulfilled a grasping function.

What am I contradicting? My claims back before I even read this study, where I proposed my own ideas that the claws were used for creating gaping wounds?

We definitely cannot assert that dromaeosaur claws were capable of slicing, at least not in smaller species, and they likely wouldn’t have to in order to be effective weapons.

Well one would think that by examining them visually without any real drag tests being done that they were valuable slashing weapons. But it is apparently not the case.

And which weapons would that be for example?

The teeth of many piscivorous animals, stegosaur thagomizers, ceratopsian brow horns, canine teeth in predatory mammals, etc.

Raptorial claws are almost always strongly curved, including those of birds of prey, which are used for stabbing. A curved shape helps the claw to stab AND hook. Furthermore, if the animal rotates its toe to puncture something with the claw, a curved claw’s tip will be pointing in the right direction, that of a straight one not. Using a straighter claw would require a major alteration in the way it uses it (pushing along the axis of the toe), and therefore in its foot morphology. This is probably not practical for an animal that uses its feet to both restrain and effectively kill prey as well as walk, because these require a degree of dexterity you won’t find in a highly cursorial animal that may be well adapted for jabbing its foot forward (like a cassowary). The claws found in accipitriforms are obviously a better analogy.

I'm sorry for not elaborating on how large the prey was in my, umm, "analogy" (for a lack of better words). I was specifically talking about use of hook-like claws on animals like large ornithopods or ceratopsians that would more-so only have a couple of puncture holes in their hides as opposed to great-enough wounds that would be deadly enough to kill them. The claws of raptorial birds, for example, are strongly hooked (just like those of dromeosaurids), and their feet are very powerful grasping weapons, but know that the majority of their prey are rodents, rabbits, and other small creatures. And plus consider how birds of prey will have a lot more foot-based leverage on their prey, whereas dromeosaurids will not (assuming that they kill large herbivores most of the time)

See what I'm saying? It is a matter of prey size; stabbing/gripping weapons in general are, without a doubt, very well suited morphologically for puncturing into small animals as opposed to killing large ones, simply because they are designed for puncture in very specific areas and create very specific wounds. For birds of prey, it is the same thing.

[theropod]

Compact means that something is restricted in dimensions in size, like a compact car. That does not make an animal more robust if their tail is simply shorter in proportion.

It does make the animal more robustly proportioned. An animal is considered robust when it’s body shape (not internal built, we are not talking about actually being robust, just about having a robust shape) would not be associated with being fragile, i.e. if there’s no elongated tail or neck or particularly thin body etc.

Fair enough, but does this outnumber the amount of small oviraptorosaurs?

I wrote "many" if I recall correctly. Gigantoraptor is much bigger than the largest predator it coexisted with according to blaze. Animals like Citipati, Anzu or Chirostenotes are still much bigger than the small dromaeosaurids we know from many Upper Cretaceous biota.

Sure, there are some really tiny oviraptorosaurs, but the point is that generally they are suited for fighting and that there are members so large that it would make sense to defend themselves from predators, because those predators were often smaller than them.

Being present in more derived animals does not automatically make something "larger"; carnotaurus was rather primitive

Carnotaurus is arguably among the most derived abelisauroids.

, yes, but allosaurs too possessed rather small forearms along with most other theropods which used their jaws as the primary means of hunting.

Allosaurs posessed fairly large forearms and hands, although they are not as elongated relative to the humeri as in some small theropods. The size of the forelimb as a whole is variable in allosauria, it ranges from extremely long in neovenatorids to intermediate in allosaurids and sinraptorids to short in carcharodontosaurs (Currie & Carpenter 2000), but what all of them have is robust built and large, raptorial claws. They may vary in size and usefulness, but their built remains fairly similar, and the predatory nature of the forelimb likely did too.

Again, if you want to look at a truly tiny forearm and manus that’s unlikely to have had a predatory purpose, look at Majungasaurus, or Carnotaurus.

Spinosaurids are an exception, but yet their arms were still not tremendously large.

They were, those of Spinosaurus were probably about the lenght of an elephant’s forelimbs (based upon Charig & Milner 1997, Dal Sasso et al. 2005).

That’s utter hogwash, not all coelurosaurs were even capable of this motion. Coelurus for example has a tiny ark of ulnar/radial motion of the wrist, Allosaurus has considerably more, albeit not as much as Deinonychus.

Allosaurus was not a coelurosaur...

No, Deinonychus and Coelurus were. You claimed only coelurosaurs were holding their hands in an adducted position, but that’s plain wrong. Some non-coelurosaurs (Allosaurus) were capable of ulnar adduction, and some coelurosaurs wheren’t (Carpenter 2002). and that they were capable of that motion doesn’t imply that was how they were holding their forelimbs most of the time, and even if it did it wouldn’t have to have implications for the potential uses in predation (if anything it would be an advantage for the manual dexterity).

And maybe I should make my point more clear. It is not that "most coelurosaurs held their forearms like that as a "resting position", but that it appears to be a trait that was developed in more advanced groups closely related to aves.

That’s besides the point. Of course the avian forelimb developed some movements not possible in other theropods, but that has little to do with how non-volant, raptorial non-avians used their forelimbs. The title of this thread is "non-locomotory limb function", locomotion includes flight of course.

It was supposed to represent a link between non-avian dinosaurs and avian dinosaurs; the more bird-like hand morphology and positioning seems to be much more well developed in related coelurosaurs.

Proportions of the hand aren’t a good link, because such features as robusticity depend on size. Also, what you were doing wasn’t making a link to birds, it was trying to set apate coelurosaurian and non-coelurosaurian theropods on the basis of their hands and their supposed different "positioning". But you cannot generalize coelurosaurs, you cannot automatically assume because they were capable of a specific motion the resulting posture would be assumed all the time, and you cannot assume this would provide you with an argument against the use of very large, raptorial hand claws in predation in the case of dromaeosaurs.

Can I have a paper for this? This is something that needs supportive evidence.

The paper is Carpenter 2002 as I think I have mentioned previously.

In return, could you give evidence for your claims about hand posture?

And besides, does that necessarily make them useful grasping tools? Think about the purpose of the hind legs and second claws again. The claws of theropods would have probably only provided support in grasping, as the hands were still quite primitive and unspecialized compared to those of animals specifically designed to grasp like primates.

Are you assuming an animal needs opposable thumbs to grasp something?
There have been claims of opposable digits in theropod manus, but none have been substantiated as far as I know. Anyway bears, cats, mustelids and rodents all use their hands for manipulating objects and none of them have opposable thumbs.

When attacking large prey for any theropod, I do not think the forearms would provide very valuable "hooking" given their morphology and reduced movement/inferior positioning overall compared to many mammals.

"Hooking" doesn’t require a lot of flexibility. Reduced flexibility may even be an advantage as it makes the grasp more stable and likely allows for greater strenght in the direction it’s moved in too.
What the hell is supposed to be inferior about their positioning?

Heck, even rodents and a few carnivoran groups can grasp things effectively.

Exactly. Again, your own arguments seem to be contradictory.

"Too" implies that someone else does. Who are you referring to, Ostrom? Kirkland and colleagues? …?

You : "As a mere gripping tool, I think the extreme size of this claw does not make sense"

I was not implying that it was used for slicing. It doesn’t necessarily make more sense for slicing either. For both, a shorter claw may be better suited.
But for puncturing the claw’s hypertrophied size and slender shape are ideal. Add the gripping/pinning down component and you know why it is laterally flattened even in small species: dorsoventral is the primary direction of loading.

Hmm, well what about the relationship between the animal's body size and the respective claw size?

There don’t appear to be relevant fluctuations here. Claw sizes even on two feet of the same eagle seem to vary somewhat, so do claw lenghts in two similar-sized specimens of Allosaurus (SMA 0005, USNM 4734), but they still fulfill the same purpose, so I wouldn’t consider a minor variation in relative claw size between Deinonychus and Utahraptor (whatever the latter’s exact body size is) important. Claws can simply vary somewhat in size at a given body size.
We don’t even know whether there is one in this case. The point is that the claw will cut more easily in larger animals, given that the force with which it can be pushed through flesh is proportional to the Dromaeosaurs weight but the force it needs for cutting only to its area.

As I said, it is of course going to be easier for Utahraptor to drive its own claw down into the hide of a prey animal than deinonychus or velociraptor, that is a given because of its much larger size. Can you quote where the paper talked about this?

Carpenter 1998 said:

The fighting pair provides the best evidence for
the function of the sickle claw in dromaeosaurid
theropods. This function is not the same as that sug-
gested by OSTROM, (1969) for another dromaeo-
saurid, Oeinonychus. Ostrom proposed that
Oeinonychus "caught and held its prey in its fore
hands and disemboweled it with the large pedal
talon" (OSTROM 1969: 143). However, in the Veloci-
raptor, the sickle claw is extended in the vicinity of
the throat(Fig. 1A). This evidence suggests thatthe
claw was not used to disembowel the prey, but that it
may have been used to pierce the jugular vei n, ca-
rotid artery, or trachea . These are areas that many
extant mammalian carnivores attack in prey.
In support for this alternative hypothesis I would
note: 1) morphologically, the long, slender, tapering
shape of the sickle claw seems best adapted for
piercing. The ventral edge (plantar side) of the un-
gual is rounded in cross-section (Fig. 2A,B) and
does not have a razor sharp edge. It is not certain
how much the keratin sheath reflected the morphol-
ogy of the ungual because the correlation between
bony core and keratin claw in extant birds and mam-
malian predators varies from little to a lot (personal
observation of museum specimens). Nevertheless,
in predators that use claws in hunting (e.g. , raptors
and cats), the claws are used to pierce and holding
prey, not for disemboweling; 2) the muscles through
which the Velociraptor pedal claw would have to cut
to disembowel its prey extend antero-posteriorly (M.
rectus abdominis), and obliquely anteriorly (M. obli-
quus extern us abdominis and M. obliquus internus
abdominis ); only the deep M. transersus abdominis
has fibers that extend parallel to the cuI. Cutting
muscle requires a sawing action, especially when
cutting across the grain ofthe muscle fibers as would
be the case for attacking the abdomen of the prey; 3)
skin is thickest on the sides and abdomen of animals
partly to protect these regions . Skin also contains a
considerable amount of elastin, a tissue that resists
tearing, but allows the skin mobility. A claw embed-
ded 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). Considering how difficult it is to cut skin
and raw meat with a dull knife (e.g., table knife), it is
highly unlikely that the less sharp dromaeosaurid
sickle claw could have cut through the thick hide and
abdominal muscles of the prey; 5) the reports of dis-
emboweling of humans or lions by ratite birds cited
by OSTROM (1969) seems to be rare and unusual
events. The disemboweling is the result of the bird's
great mass behind the kick ratherthan cutting by the
claws because none of the pedal claws bear any re-
semblance with the laterally compressed sickle claw
of the dromaeosaurid foot. The light weig ht of most
dromaeosaurids (30-80 kg , OSTROM , 1990) makes it
doubtful that they had enough mass to effectively
disembowel their prey with their sickle claw. Further-
more , it seems doubtful that the dromaeosaurid
could hop one legged along side of a fleeing prey
while sawing through the tough hide and musclewith
the claw of its other fool.

This sums up Carpenter’s view on the issue of how small to mid-sized dromaeosaurids used their hind claws.

What am I contradicting? My claims back before I even read this study, where I proposed my own ideas that the claws were used for creating gaping wounds?

No, the claims you just made, about the claw being used for tearing or cutting, are contradicting the study you posted, which suggested them to be used for gripping (that, in turn, you used to support your claim that the manual unguals were somehow unnecessary and useless structures, despite them reaching over 20cm in lenght!).

Well one would think that by examining them visually without any real drag tests being done that they were valuable slashing weapons. But it is apparently not the case.

At least not in small genera, no. Not sure how visuals could help you, I guess most people who claim they looked like they were good for slashing haven’t even seen one from more than one angle, let alone seen a crossection.

The teeth of many piscivorous animals, stegosaur thagomizers, ceratopsian brow horns, canine teeth in predatory mammals, etc.

And are there any claws among those?

I'm sorry for not elaborating on how large the prey was in my, umm, "analogy" (for a lack of better words). I was specifically talking about use of hook-like claws on animals like large ornithopods or ceratopsians that would more-so only have a couple of puncture holes in their hides as opposed to great-enough wounds that would be deadly enough to kill them.

How exactly are a couple of puncture holes not deadly enough to kill them? Eagles have been recorded preying on animals 50 times their weight using their claws (Mason 2000), which are puncturing tools built for grasping and pinning down prey (Fowler et al. 2011)–and guess what, they are also curved!
Also, even if this were a valid point, keep in mind smaller dromaeosaurs like Deinonychus probably used gregarious hunting techniques (Maxwell & Ostrom 1995, cited in Holtz 2003).

The claws of raptorial birds, for example, are strongly hooked (just like those of dromeosaurids), and their feet are very powerful grasping weapons, but know that the majority of their prey are rodents, rabbits, and other small creatures. And plus consider how birds of prey will have a lot more foot-based leverage on their prey, whereas dromeosaurids will not (assuming that they kill large herbivores most of the time)

Leverage doesn’t help eagles when they kill large prey, unless you are suggesting they would wrestle down an antilope or calf. They kill such large prey by means of dealing very deep stabbing injuries.

See what I'm saying? It is a matter of prey size; stabbing/gripping weapons in general are, without a doubt, very well suited morphologically for puncturing into small animals as opposed to killing large ones, simply because they are designed for puncture in very specific areas and create very specific wounds. For birds of prey, it is the same thing.

That I find very funny considering it’s birds of prey that have the largest recorded relative prey size of any tetrapod.

---

REFERENCES:
Burch, Sara; Carrano, Matthew: An articulated pectoral girdle and forelimb of the abelisaurid theropod Majungasaurus crenatissimus from the Late Cretaceous of Madagascar. Journal of Vertebrate Paleontology, vol. 32 (2012); 1; pp. 1-16
Carpenter, Kenneth: Evidence of predatory Behaviour by carnivorous Dinosaurs. Gaia, vol. 15 (1998); pp. 135-144
Carpenter, Kenneth: Forelimb Biomechanics of Nonavian Theropod Dinosaurs in Predation. Senckenbergiana lethaea, vol. 82 (2002); 1; pp. 59-76
Charig, Alan; Milner, Angela: Baryonyx walkeri, a fish-eating dinosaur from the Wealden of Surrey. Bulletin of the Natural History Museum, London (Geology), vol. 53 (1997); 1; pp. 11-70
Currie, Philip; Carpenter, Kenneth: A new specimen of Acrocanthosaurus atokensis (Theropoda, Dinosauria) from the Lower Cretaceous Antlers Formation (Lower Cretaceous, Aptian) of Oklahoma, USA. Geodiversitas, vol. 22 (2000); 2; pp. 207-246
Dal Sasso, Christiano; Maganuco, Simone; Buffetaut, Eric; Mendez, Marco: New Information on the Skull of the enigmatic Theropod Spinosaurus, with Remarks on its Size and Affinities. Journal of Vertebrate Paleontology, vol. 25 (2005); 4; pp. 888-896
Holtz, Thomas: Dinosaur Predation: Evidence and Ecomorphology Topics in Geobiology vol. 20 (2003); pp. 325-340
Kirkland, James; Gaston, Robert; Burge, Donald: A Large Dromaeosaur (Theropoda) from the Lower Cretaceous of Eastern Utah. Hunteria, vol. 2 (1993); 10; pp. 1-16
Mason, J: Golden Eagle Attacks and Kills Adult Male Coyote. Journal of Raptor Research, vol 34 (2000); 3; pp. 244-245
Ruiz, Javier; Torices, Angélica; Serrano, Humberto; López, Valle: The Hand Structure of Carnotaurus sastrei (Theropoda, Abelisauridae): Implications for Hand Diversity and Evolution in Abelisaurids. Palaeontology, vol. 54 (2011); 6; pp. 1271–1277

[theropod]

Aug 20, 2014 22:43:43 GMT 5 creature386 said:

I am not sure about this. I know that the coracoid is connected to the biceps and such, but I am not sure if it is connected to the neck muscles. Given that it may be large in overall dimensions, but very short, I doubt that it was connected to arm and neck muscles.

Reading Bakker (1998) it appears that muscles from the shoulder region (m. levator scapulae, m. sternocleido mastoideus) attach to the cervical ribs, which in turn are where m. iliocostalis capitis originates, so the shoulder musculature probably does play a role in neck mechanics, even though it cannot do a lot on its own.
I’m not sure whether any muscles originating from the coracoid are involved here, but some definitely pass over it.

References:
Bakker, Robert: Brontosaur killers: Late Jurassic allosaurids as sabre-tooth cat analogues. Gaia, vol. 15 (1998); pp. 145-158
Snively, Eric; Russell, Anthony: Functional Variation of Neck Muscles and Their Relation to Feeding Style in Tyrannosauridae and Other Large Theropod Dinosaurs. The Anatomical Record, vol. 290 (2007); pp. 934-957

[theropod]

Sept 27, 2014 2:24:45 GMT 5 Godzillasaurus said:

Although dromeosaurid skulls were definitely not the strongest or the most powerful, they still lack the capabilities that allow birds like eagles and hawks to be effective talon-based hunters.

Please elaborate.
You are right if what you mean is their inability to fly, but they were obviously effective talon-based hunters. There firstly is a fossil proving that, and there secondly is a claw and digit morphology for which no other than a primarily predatory purpose seems to make sense.

A 500kg+Utahraptor is obviously not an arboreal animal (also, many other aspect of most dromaeosaur’s morphology is inconsistent with an arboreal lifestyle, what their ancestral state was is another matter but it isn’t relevant)–and yet it shows the same hypertropied claw on its foot. And it’s only the second toe, which to top it all is built to suspend the claw above the ground while walking, that bears such a large claw. Climbing isn’t a satisfactory option here.
And what else is there left? Digging? Not worth serious consideration. Animals using their claws for digging (like bears, dogs, mustelids, moles) don’t carry them above the ground to prevent them from getting dull, their claws are relatively straight, and neither laterally compressed, nor particularly sharply pointed.

They were definitely adapted for what you call talon-based hunting.

[theropod]

Sept 27, 2014 2:22:50 GMT 5 Godzillasaurus said:

Whether it could or could not flex its metatarsals like that does not mean that it actually used it for actually grabbing things like birds of prey due today. It is all about how it moved around; birds of prey hunt by striking from the air (and lack gripping ability in their arms completely), so naturally feet that are designed for clamping small animals like rabbits and rodents would be ideal for that sort of lifestyle. For terrestrial-based theropods such as deinonychus, catching even small prey with toe enclosure would be inefficient, as the creature would have already been able to use its jaws to catch small things.

The redundancy of the limbs and claws only becomes much greater as theropod jaw strength and size intensifies, as in many large-jawed theropods that is their primary hunting tool in general. Even though dromeosaurids were probably not as reliant on jaw usage as many larger macrophagous groups, the function of their hind legs for grabbing (grabbing and grappling are two different things) would still be ineffective.

Firstly, no animal can flex its metatarsals (unless maybe if you break them). Metatarsals are rigid structures, at least along their long axis, if they were supposed to be flexed they wouldn’t be bones used in supporting body weight, and not made out of bone at all for that matter.

Secondly, dromaeosaurids lacked an opposed hallux, so naturally they are never going to grip the same way as animals with an opposed hallux would. But in no way does that imply that they didn”t grip things with them. That they had considerable potential for flexion does suggest increased dexterity in gripping and a more secure grasp.

Your jaw argument also doesn’t work. By the same reasoning, raptors could use their jaws to catch small prey too, but they don’t do that. The feet are great for catching small prey, they are fast, powerful and already close to the ground, all that without having to concentrate additional mass in the head (which would inevitably impair maneuverability) if they have to restrain struggling prey. And using them doesn’t interfere with sensory function as moving the head would. All these are reasons why dromaeosaurs and accipitrids both tend to use their claws rather than their teeth for the securing and killing of prey.

Thirdly, "redundancy" and "ineffective" are without doubt the most misplaced word that you could possibly use to in conjunction with dromaeosaur limbs and claws. That these claws were effective at stabbing and gripping is evident from their anatomy, if you think otherwise you should provide reasons why.

And finally, you are confusing me. A short time ago you argued dromaeosaurids used their hindlimbs for grappling and didn’t need their forelimbs for this (although admittedly in that discussion you seemed to contradict yourself on this matter too). Now you claim the exact same thing about the forelimbs!

[creature386]

Sept 27, 2014 2:22:50 GMT 5 Godzillasaurus said:

Whether it could or could not flex its metatarsals like that does not mean that it actually used it for actually grabbing things like birds of prey due today.

What is your opinion on the reason for their ability to flex? Do you believe in a combination of fore- and hindlimb use that was not like the mantling hypothesis in Ausar's reference paper?

Sept 27, 2014 2:22:50 GMT 5 Godzillasaurus said:

It is all about how it moved around; birds of prey hunt by striking from the air (and lack gripping ability in their arms completely), so naturally feet that are designed for clamping small animals like rabbits and rodents would be ideal for that sort of lifestyle.

I believe a decent jumping ability would already be enough, they would only need to get on the backs oft their prey because the model we are discussing suggests grasping prey and pinning it down with the body mass.

Sept 27, 2014 2:22:50 GMT 5 Godzillasaurus said:

For terrestrial-based theropods such as deinonychus, catching even small prey with toe enclosure would be inefficient, as the creature would have already been able to use its jaws to catch small things.

The paper Ausar cited suggested a use of the grasping strategy for prey subequal in size to the predator, hence not prey that is as small as that it could be simply killed with one jaw bite or even picked up with the jaw.

EDIT: Ooops, I didn't see that theropod already replied, I am sorry!
I will also move this from the Animal Bite's thread to the thread where theropod replied.