-2
$\begingroup$

The first terrestrial animals used sprawling locomotion. Is the knee and elbow jointed perpendicular to the joints in erect locomotion? It is easy to assume so, based on how the limbs move in sprawling locomotion.

enter image description here

There was a question on exactly what is meant with jointed perpendicularly. It means the joint angle is perpendicular. Here is a rough ugly sketch, does not have to be a joint like that, question is if the movement in the joint is in any way in that direction.

enter image description here

Here, Baier seem to support that the knee and elbow joint in sprawling locomotion supports movement perpendicular to the simple hinge joint in erect locomotion, which is exactly what question is asking.

"The elbow was not a simple hinge; motion entailed substantial abduction/adduction"

Baier, D. B., & Gatesy, S. M. (2013). Three-dimensional skeletal kinematics of the shoulder girdle and forelimb in walkingAlligator. Journal of Anatomy, n/a–n/a. doi:10.1111/joa.12102

Edit: the "diagram" caused some controversy in comment section. It was a copy+paste, simplest fastest possible I could make, in response to comment "What do you mean by "jointed perpendicular"?", because I considered that comment to be asking something that is clear. It is meant to show the perpendicular movement direction, not the joint design. It is not needed for the question, at all.

Improve this question
$\endgroup$
  • $\begingroup$ They don't appear to be in the images, why do you think that they would be? $\endgroup$ – Bryan Krause♦ Nov 17 '20 at 21:01
  • $\begingroup$ It is easy to assume so, based on how the limbs move in sprawling locomotion. In that particular image, they are jointed perpendicular, but it is a rough schematic, could be wrong. $\endgroup$ – Reding Nov 17 '20 at 21:06
  • 1
    $\begingroup$ What do you mean by "jointed perpendicular"? They appear to be jointed in the same orientation in both pictures. $\endgroup$ – Bryan Krause♦ Nov 17 '20 at 21:07
  • $\begingroup$ What do these diagrams have to do with the comparison in the original images? $\endgroup$ – Bryan Krause♦ Nov 17 '20 at 21:40
  • 1
    $\begingroup$ This question could be better explained, perpendicular to a previous orientation? what the migration of the joint and bone orientation is through evolution? perperdicular is a very specific word which requires more specific references to it's surroundings than you give. Are you saying that the knee could fit image 4 rather than image 3? $\endgroup$ – aliential Nov 18 '20 at 1:19
0
$\begingroup$

This article by Baier seem to support that the knee and elbow joint in sprawling locomotion supports movement perpendicular to the simple hinge joint in erect locomotion, which is exactly what question is asking. The joints in sprawlers also supports flexion/extension axis though, and the question could have been a bit clearer on that. If I misinterpret Baier feel free to point that out (but since besides flexion/extension, and pronation/supination, it is what is left, I think I do not), and if not, question answered.

"The elbow was not a simple hinge; motion entailed substantial abduction/adduction"

References

Baier, D. B., & Gatesy, S. M. (2013). Three-dimensional skeletal kinematics of the shoulder girdle and forelimb in walkingAlligator. Journal of Anatomy, n/a–n/a. doi:10.1111/joa.12102

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.