Neutral (i.e. semi-supinated or non-pronated) hands and quadrupedalism

[amargasaurus cazaui]

If his hands were supinated, and were unable to pronate, there is no way that he could have placed much weight on the hands to walk. There simply would not be aqequate strength or support for a four legged stance in a supinated position. Accepting the supinated position of the hands almost demands the animal be limited to bi-pedal locomotion. At least from my understanding viewing both the animals bones and the opinions offered so far, that is what is suggested.

[amargasaurus cazaui]

If his hands were supinated, and were unable to pronate, there is no way that he could have placed much weight on the hands to walk. There simply would not be aqequate strength or support for a four legged stance in a supinated position. Accepting the supinated position of the hands almost demands the animal be limited to bi-pedal locomotion. At least from my understanding viewing both the animals bones and the opinions offered so far, that is what is suggested.

I do think we are off thread here and distracting from this mans exceptional collection so perhaps an admin could split us off to a seperate thread. I am enjoying the discussion immensely but wish not to distract from the collection the thread was intended to represent.  Please pardon me for doing so, and thanks all

[Himmapaan]

Just a note to point out that this topic has been split from Helge's collection thread. There were a few stray comments in between some relevant posts to Helge's original thread which I didn't include in the split, in case anyone wished to refer to them.


Many ornithischians have neutral hands but are entirely or facultatively quadrupedal. Ceratopsians and iguanodontians for instance. I used to wonder at their weight-bearing capacity myself, but I don't think it makes a difference so long as there is enough surface 'purchase' upon the ground. If you were to try placing your own hands in a neutral position yourself, you would still be able to place enough weight on them without difficulty. Discomfort only occurs because we are not constructed for such a stance and locomotion, but the dinosaurs in question were. Also, in the case of ceratopsians at least, their elbows are angled out slightly so that the hands result in a diagonally palm-facing position, as opposed to being in direct parallel (if that makes any sense at all), which would also have lent more strength.

[Gryphoceratops]

Modern quadrupedal archosaurs pretty much walk with their palms in anyway. 

http://www.youtube.com/watch?v=K9kHlIGryro

http://www.youtube.com/watch?v=NnFBVGUkAC4

[amargasaurus cazaui]

Just a note to point out that this topic has been split from Helge's collection thread. There were a few stray comments in between some relevant posts to Helge's original thread which I didn't include in the split, in case anyone wished to refer to them.


Many ornithischians have neutral hands but are entirely or facultatively quadrupedal. Ceratopsians and iguanodontians for instance. I used to wonder at their weight-bearing capacity myself, but I don't think it makes a difference so long as there is enough surface 'purchase' upon the ground. If you were to try placing your own hands in a neutral position yourself, you would still be able to place enough weight on them without difficulty. Discomfort only occurs because we are not constructed for such a stance and locomotion, but the dinosaurs in question were. Also, in the case of ceratopsians at least, their elbows are angled out slightly so that the hands result in a diagonally palm-facing position, as opposed to being in direct parallel (if that makes any sense at all), which would also have lent more strength.

I wanted to say thanks for splitting our discussion off, I felt bad for distracting from that mans gorgeous collection and photography, and thanks for your patience with me for having done so.
As to the hands and this debate, I am still waiting to here from the lab that prepped the animal, as to the justification for placing the hands in a pronated pose, given conventional thinking. It is my guess that it might be related to how the bones are located to one another have to be drilled or mounted. I do know if it is a non issue for them I am going to request , the neutral pose for the hands as described earlier with palms facing. I like the idea for another reason as well. With the hands sideways it would far easier to view the digits of the hand and the claws as well.
I am amazed that anyone was able to catch the hands being placed wrong. When I saw the mount the first two things i made note of, were the missing processes of the back discs, and the fact the dinosaur does not have the sclerotic eye rings these animls should have had.
The dinosaur done by Aron to my eyes is also missing the rings unless they were beneath the skin level which I believe would fail to serve purpose.  The lab explained for me the sclerotic rings were sometimes restored, and for x amount of investment, I too could purchase them. I did not feel it a worthwhile investment for the cost and passed.

[Dinoguy2]

Note that in quadrupedal archosaurs, some twisting or contortion always accompanies four-limbed walking. In crocs, the palms face back due to the prawling posture or the arm. In ceratopsians, the palm actually faces the middle, but the outer fingers are enlarged and the inner ones reduced, basically making the new 'main' fingers point forward rather than outward. In sauropods, the bones of the forelimb are twisted around each other, forcing the palm to point backward--sort of a permanent pronation, but not at the wrist.

[Horridus]

The dinosaur done by Aron to my eyes is also missing the rings unless they were beneath the skin level which I believe would fail to serve purpose.

Sclerotic rings are always beneath skin level - just look at any bird. (Or have I missed something here...?)

[amargasaurus cazaui]

The dinosaur done by Aron to my eyes is also missing the rings unless they were beneath the skin level which I believe would fail to serve purpose.

Sclerotic rings are always beneath skin level - just look at any bird. (Or have I missed something here...?)

I was thinking they might be more noticeable in form and more obvious I guess. When i see the reconstructions they look very solid and large in the eye orbit.

[amargasaurus cazaui]

Note that in quadrupedal archosaurs, some twisting or contortion always accompanies four-limbed walking. In crocs, the palms face back due to the prawling posture or the arm. In ceratopsians, the palm actually faces the middle, but the outer fingers are enlarged and the inner ones reduced, basically making the new 'main' fingers point forward rather than outward. In sauropods, the bones of the forelimb are twisted around each other, forcing the palm to point backward--sort of a permanent pronation, but not at the wrist.

I just heard back from the lab that has done this mount. I do state up front this is a credited and quite familiar paleontologist that regularly sells these animals and they specialize in the particular species.  Having sold more than three hundred mounted specimens, and never an issue yet.They are based in the UK and are generally well known in this particular dinosaur and its mounting.
This was his commentary on the discussion. I was a bit surprised as you might be as well. I am copy pasting by the word, so this was his exact response.



"Re. manus orientation - they should definitely not be supinated (palms facing upwards).
We have mounted the manus pronated (virtually every Psittacosaur mount has pronated manus).
I have only seen maybe two mounts where they posed the manus with palms facing inwards - which is what the paper suggests to be natural articulation.
It seems highly doubtful to me that Psittacosaurus could not  place it forefeet on the ground.
Certainly, the species was obligate biped - bipedal locomotion being the norm.
I'm certain however that grounding the forefeet would be neccessary for numerous essential functions.
One paper stating otherwise, does not prove the point.
I could elucidate further, but unfortunately time presses - eg. validity of preservation robustness of articulating joints is questionable..... quality of specimens used in the study.......does this mean other obilgate bipedal dinosaurs couldn't ground their forefeet.....?

[Himmapaan]

Well they shouldn't be facing upwards, clearly (this is why I still don't like 'supinated' to describe palm-facing hands. It's misleading). But inwards, yes. And again, neutral hands do not negate quadrupedalism.

But what do I know? I'm only an ignorant layperson following the lead of the scientific consensus. 

[amargasaurus cazaui]

Well they shouldn't be facing upwards, clearly (this is why I still don't like 'supinated' to describe palm-facing hands. It's misleading). But inwards, yes. And again, neutral hands do not negate quadrupedalism.

But what do I know? I'm only an ignorant layperson following the lead of the scientific consensus. 

I was somewhat surprised myself, as it obviously seems an issue he has dealt with a few times. He did quite clearly distinguish between supinated and pronated in his answer however, despite referring to supinated as hands up, in nature. I am tempted to ask if the wrists on the dinosaur could be pinned so that you could rotate the manus, as he referred to them, into either mode of display. To me that would seem a highly logical choice, leaving you the option to display in either mode.
And no you are highly intelligent from what I am seeing and reading. Before this discussion I had no concept of the difference myself, and you have helped educate me in the matter

[Gryphoceratops]

Yeah the palms would def be facing each other but this doesn't mean they couldn't drop down to all fours.  In fact, they probably did.  There are tracks from other dinosaurs like prosauropods with inward facing palms resting or supporting their bodies like that. 

[Patrx]

Yeah the palms would def be facing each other but this doesn't mean they couldn't drop down to all fours.  In fact, they probably did.  There are tracks from other dinosaurs like prosauropods with inward facing palms resting or supporting their bodies like that.

Exactly.  Bigger ceratopsians like Triceratops had neutrally-positioned hands as well; and they were entirely quadrupedal.

But what do I know? I'm only an ignorant layperson following the lead of the scientific consensus. 

...no you are highly intelligent from what I am seeing and reading. Before this discussion I had no concept of the difference myself, and you have helped educate me in the matter

Quite right. Niroot, I am thankful to you for correcting my initial misuse of the term "supinated"

[amargasaurus cazaui]

I did view a picture of the mount in Indianappolis Childrens museum today and to my eyes it is mounted in a position that is as you have described...semi-supinated , from what I can see. Neither up nor down, just tilted slightly upwards. but clearly facing one another.
I might ask if the sleeves could be worked to produce a mount that can be supinated or pronated with a simple twist as a simple resoloution to the issue. To me that would seem the most logical choice at this point.
I do know he sure seemed quite determined and passionate in his response.

[Aaron Doyle]

The dinosaur done by Aron to my eyes is also missing the rings unless they were beneath the skin level which I believe would fail to serve purpose.

As odd as this may sound sclerotic rings are actually bones within the eyeball itself.  I studied them briefly while working on a project for the Pittsburgh Aviary.  They stiffen and reshape the front of the eyeball so that an animal can fit a more substantial eye in a shallow sock.  I've handled rings from eagles and they are very delicate, almost paper thin.  If that is any indication it's no wonder they rarely fossilize.  Although I'm not sure how thick the sclerotic rings of non-avian dinosaurs were.

[amargasaurus cazaui]

The dinosaur done by Aron to my eyes is also missing the rings unless they were beneath the skin level which I believe would fail to serve purpose.

As odd as this may sound sclerotic rings are actually bones within the eyeball itself.  I studied them briefly while working on a project for the Pittsburgh Aviary.  They stiffen and reshape the front of the eyeball so that an animal can fit a more substantial eye in a shallow sock.  I've handled rings from eagles and they are very delicate, almost paper thin.  If that is any indication it's no wonder they rarely fossilize.  Although I'm not sure how thick the sclerotic rings of non-avian dinosaurs were.

That makes perfect sense and thanks for explaining it for me so well. I had a completely inaccurate concept of what they would be like in my mind. I redact my comment regarding your model regarding the rings, it was not well founded in light of these things.
I did wish to compliment you on the model of the psittacosaur. I want to get one as soon as possible for myself, my only problem will be having someone paint it up for me so it looks nice. I dont paint worth anything at all. I have recently purchased a psittacosaur skeleton and would like to get the model to display along side. I did wish to ask ..just how large is he in terms of inches or in terms that i could visualize? The skeleton i bought was basicaly 25 inches long and 14 1/2  inches tall and if your little guy is 1/12 scale, that would mean he is two inches long roughly?

[amargasaurus cazaui]

A friend chose to get me a Shapeways Model Psittacosaur this evening so I will be getting one it seems. I was unsure what to tell her regarding the material to choose, as there seem several options. She opted for the detail version at around 68 dollars...but can any of you avid modelers explain the differences, pros, cons etc of the possible choices?
While on the topic, I wondered if anyone knows of any other decent sculpts of the animal? I am aware of the Carnegie piece, but to me it doesnt really quite do it for me. I am really wanting any artwork, sculpts or pieces that deal with the dinosaur to work with, so if anyone has suggestions, fire away !!

[amargasaurus cazaui]

I have been studying the dinosaur and his bones and I have run across a question I hoped someone might be able to help with . The Psittacosaur I purchased was mounted in a pronated condition, although most here in the forum felt he should have neutral or semi supinated hands. I had been pondering if I might be able to modify the skeleton as it is mounted so that the hands could be placed in either mode depending on current thinking. As I look at the specimen I am wondering, do you rotate the two arm bones on each side so they are spaced above and below one another, so the wrist areas match better or do the arm bones stay side by side? In other words would you begin supinating the hands at the elbow or wrist?  I will attach a picture of the arms so you can better view what I am asking. Thanks

[Himmapaan]

Ah, that's probably where the mount was incorrect in the first place; the hands should remain in exactly the position you have now, but the forearm bones should be rotated. Radius above ulna, not side by side.

If you place your own hands in a neutral position and feel your forearm bones, that is just how they should be. When we pronate our hands, these bones twist and cross one another (rather than both rotating together to parallel each other as a single unit). This is what dinosaurs are unable to do, hence hands placed permanently in a neutral position.

[amargasaurus cazaui]

Ah, that's probably where the mount was incorrect in the first place; the hands should remain in exactly the position you have now, but the forearm bones should be rotated. Radius above ulna, not side by side.

If you place your own hands in a neutral position and feel your forearm bones, that is just how they should be. When we pronate our hands, these bones twist and cross one another (rather than both rotating together to parallel each other as a single unit). This is what dinosaurs are unable to do, hence hands placed permanently in a neutral position.

So if I understood correctly I should be able to just rotate the joint at the elbows so the bones are above and below rather than side by side, as you stated, BUT does this mean allow the hands to rotate with them?
If I am understanding correctly you are suggesting leaving the manus oriented at the wrists as they are now and doing the turning at the elbow only, which of course would have the effect of supinating the hands if rotated properly.