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QUOTE (Jarlaxle @ Feb 3 2023, 09:55 PM)

QUOTE (Disgustedorite @ Feb 4 2023, 03:02 AM) QUOTE (Jarlaxle @ Feb 3 2023, 08:47 PM) While I am still cautious with how well I'm interpreting the information, "have nothing to do with the ankle joint" is almost certainly false: QUOTE Eight modelled ostrich limb muscles also show this pattern: the AMB1, AMB2, IC, ITCa, ITCp, ITM, ITCR and ISF exhibit stabilization function in flexion-extension (Figs. 9 and 10). Weaker evidence for self-stabilization is present for the OM muscle in hip ab/adduction (Fig. 14) and the four ankle flexors in flexion/extension (TCf, TCt, EDL, and FL; Fig. 18), so any self-stabilization properties must be interpreted as being largely restricted to the hip’s flexion-extension function (see also Table 4). QUOTE Ankle musculature displays fairly congruent patterns in our model and S.E.A. and B.A.S.’s data (Figs. 18 and 19). The TCf and TCt heads generally have an ankle extensor action, like the EDL muscle group does, albeit with some switches to extensor action with extreme (dorsi)flexion in the B.A.S. dataset (and our TCf). Surprisingly, ankle extensors reveal more variation: our FDL’s ankle extensor moment arm is almost twice as large of that in the S.E.A. and B.A.S. data, showing little change with ankle posture, whereas the B.A.S. dataset exhibited a decreased moment arm with flexion. Our other digital flexor muscles (FPD3, FPD4) and those of S.E.A. display roughly similar values but opposite trends, increasing their moment arms with ankle flexion in our model. Our FL muscle’s extensor moment arm is smaller than those of S.E.A. and B.A.S. The model of B.A.S. had a M. fibularis brevis (FB) muscle (Fig. 18), which is reduced to a ligament in Struthio and thus not included in our model; no studies have data for the ligamentous M. plantaris (Zinoviev, 2006). The extensor moment arms for our gastrocnemius muscles are all identical and fairly constant with ankle flexion, whereas the curves for the data of S.E.A. and B.A.S. increased steadily and tended to be larger (Fig. 19). Source: https://nmbl.stanford.edu/publications/pdf/...chinson2015.pdf Not to mention, what's the point on insisting on a joint that wouldn't allow a sauceback to survive a mild kick from the side or to stumble over a rock? You can't reasonably argue against the need to withstand lateral forces and then have it push against air resistance in the same breath, that's absurd. That first paragraph appears to be saying, in layman's terms, "the evidence that these might stabilize the ankle is very weak, stabilization is probably restricted to the hip region". The hip can move laterally in both birds and saucebacks, and is also what you use to move your leg to catch yourself when you stumble or get kicked from the side. The second paragraph has nothing to do with lateralmotion of the ankle joint. Not quite. The 2nd paragraph looks like its saying that the specific ankle muscles maintain their tension on the ankle throughout the walking stance regardless of pose pulling underneath the ankle from both sides consistently throughout the step, so a slightly more thorough reading of the 1st paragraph is "we do have evidence for stabilization in the knee muscles but we acknowledge that it isn't as strong or clear cut as the evidance for stabilization from the hip muscles". And before you conclude that gives you enough leeway to leave the biat ankle without any muscles for withstanding lateral forces, that's still not viable once you are using those limbs to withstand air resistance during flight.

Can you quote specific parts that say what you claim and translate them to layman's terms to prove that's what it says? Because to me it just looks like you're reading whatever you want into that and either assuming none of us understand it well enough to disprove it, or you yourself really believe that's what it says, and I think we need to break it down to find out which one it is.

Also, if biats need to have a side to side stabilizing muscle for their albert joint in order to keep it stable in flight, where, exactly, is the side-to-side elbow stabilizer muscle or tendon on this bird wing diagram?



As, much like the heel, a bird's elbow is also a hinge with literal solid bone flanges to keep it from moving side to side.

Oh.

Would patagium muscles exist in song sauce pipers?

Patagialis Longus in birds, but for the patagium behind the leg that should work nicely as an origin muscle for the grashof, it's mostly tendon from what I can tell, but I haven't dug deep at all.

There should be patagia muscles in biats, in general. As they are for moving skin rather than actually concerning the motion of the bones themselves, they are excluded in the musculoskeletal diagrams. Many bird diagrams also exclude the patagia muscles, but I chose one that includes them for the sake of making sure it was a complete one.

Dorite was right about their bird ankles and wings, I wasn't sure to what extent I was allowing confirmation bias to color my interpretation of the research (the ground for my interpretation felt shaky at the time), so I just followed my own advice and asked the researcher:


The interlocking of joint in turn inspired the U joint design concept:
By increasing the curve at the top of the cannon bone, you create a fulcrum point to shift the way the Albert sits on the cannon bone.
By extending a flattened bone part on the rear of the connection, we create a lock mechanism that prevents lateral movement when locked.
As the toe extensor muscle gets pulled (the muscle on the front of the cannon bone), the cannon bone connection would lean forward towards the front of the Albert bone, breaking away at the rear & releasing the lock, leaving the connection to lean along the curved front, which can be shaped more like a ball socket joint, though by flattening the front of the ball and extending the rim of the Albert bone in front of it we can restrain it to function as a lateral joint.
Restraining it would allow the current muscles to control forward-backward motion from the top of the Albert joint while creating some degree of lateral control by pulling on the extensor and flexor muscles of either toe at the same time to shift left to right without pulling in the toes themselves, which is just enough to apply lateral control (needed to realign the lock), but not enough to apply much in terms of force, which would still depend on the momentum generated by the grashof system (which incidentally opens up the role of locally applied lateral forces for future evolutionary changes, like colddiggers shrunken cannon bone idea).
Once aligned pulling on the wing toe flexor muscles to fold up the wing would lock the mechanism back into place, leaving the Albert to function as a forward-backward hinge again.

Hopefully the verbal explanation makes sense for now. While there are several ways to do this, this is my favorite one mechanically, and it requires the least changes. The part I am still trying to figure out is the evolutionary story behind these developments happening together:
1. An increased curve on top of the cannon bone acting as a fulcrum point
2. An extended lock from the rear of the cannon bone into the Albert joint (or vice versa).
3 A flattening of the front of the cannon bone to restrain the resulting ball into lateral motion
4. The thick knee muscle used together with lateral movement for ourbursts of speed

The 4 have to weave together as part of the songsauce's evolutionary story

(Note: Based on visuals it looks like the biats cannon bone locks into the Albert and stays in place while Albert locks into the side ridges of the shin to form the hinge. If my impression of the skeleton and muscle diagrams is incorrect the system above can be reversed on either side, though the specifics would need to be adapted).

This post has been edited by Jarlaxle: Feb 5 2023, 06:26 PM

@Jarlaxle Heads up, I've gotten requests to not have active threads in the Graveyard, so I have repurposed the Hold as a location for posts that aren't accepted for the current gen to continue to be worked on. I am relocating this thread to that subforum now.