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One unique way of making a reptilian humanoid is a rather fanciful joint in which human-like shoulders, including the extension of the shoulderblade, are seemingly stapled to the sides of the ventral face of the chest. Such an anatomy is seen, for example, in the lizalfos from LOZ:BOTW

A botw Lizalfo

There is an issue with this design, that being the internal anatomy of this structure: Unlike the human form, a normal shoulderblade would intersect through the ribs, which is not possible. There also seems to be issues with the muscles. While we could reinvent everything, that is a bit of a cop-out here

Could these shoulders be made to fit together within the set of bones and muscles in the tetrapods?

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  • $\begingroup$ To me this looks like the neck is a bit longer and thicker than we're used to, while the ribcage and shoulder bones are where they are supposed to go. $\endgroup$
    – KeizerHarm
    Jun 28 at 21:31
  • $\begingroup$ @KeizerHarm This question is about the shoulders $\endgroup$ Jun 28 at 21:32
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    $\begingroup$ @IchtysKing look up references of chameleon skeletons. Or of the T-Rex for an even more extreme case of arms on the ventral side. $\endgroup$
    – KeizerHarm
    Jun 28 at 21:41
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    $\begingroup$ There does not appear to be anything wrong with the anatomy, just don't try to use Humans as reference, humans are extremely derived creatures, human's unusual anatomy is not a a good reference for most non-human things. $\endgroup$
    – John
    Jun 29 at 1:36
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    $\begingroup$ Only problem I see with this guy is he might be very front-heavy, especially with that spear. You might consider making the tail longer or thicker to provide a counterbalance. Larger feet (especially towards the front) would also help keep this thing upright. Also thicker legs, bent towards the front, to provide more support below the center of mass. $\endgroup$ Jun 29 at 19:17

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Your anatomy is fine

There is nothing impossible about your creatures shoulder anatomy.

The human shoulder joint is very unusual - using it a reference is just going to throw you off. Looking at most animals, the shoulder blade is vertical on the side of the body. Apes in general have derived shoulders evolved for a particular type of climbing. As apes we also have chest cavities that are wider than they are tall which is also weird - most animals have a narrow but deep chest.

A few things your anatomy tells us

  1. The shoulder joint of your creature is not very muscular meaning it is not very strong. Which kind of makes sense - if it had anymore mass in the front half of its body it would fall over.

  2. It probably can't raise its hands far over its head, or if it can, its arms can go back further than vertical.

enter image description here

enter image description here

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The Spine is Not Where You Think

If I understand correctly the problem is arms and legs are usually anchored to the spine. But how can that be if the spine is located here?

enter image description here

The solution is to have the spine here instead:

enter image description here

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    $\begingroup$ forelimbs are not anchored to the spine, not in any vertebrate. that is why you can shrug your shoulders. $\endgroup$
    – John
    Jun 29 at 18:04
  • $\begingroup$ @John Of course you are right. Just me being a silly sausage (as usual). $\endgroup$
    – Daron
    Jun 30 at 11:55
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Second elbow

The creature you refer to looks like a 90s alien with an easy skeleton to animate for games. Another issue that strikes me is the 360 degrees freedom of that shoulder! These beasts you only find in games..

enter image description here

https://www.google.com/search?q=lizalfos&tbm=isch

Consider a second elbow, like in arthropods. The "upper upper" arm can be firmly attached to a narrower humanoid shoulder, which need not be too prominent. Together, the two elbows will provide angular freedom the lizalfos got used to. The upper elbow gives xz-freedom, the lower elbow handles yz-freedom. Less bone mass and muscle is required to support the shoulder, muscle is in the upper arms around the elbows. The shoulder can be less prominent, but still has to carry the mass.. this creature has huge arms, when the musculature would be complete !

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  • $\begingroup$ The question clearly states to stay within normal tetrapod anatomy. How is this achieved here? $\endgroup$ Jun 28 at 21:29
  • $\begingroup$ @IchthysKing if you want a normal tetrapod, the shoulders should be placed more forward. But that answer is trivial. This beast has a shoulder circular bearing halfway the ribs. No tetrapod has that because there is no mount on the side of the ribs. The animal as shown in Google Images (most variants) seems bipedal (yours is bipedal ? ) think of weaker, lighter arms ? $\endgroup$
    – Goodies
    Jun 28 at 21:45
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Flamingo Knees

enter image description here

What look like shoulders are actually elbows. The real shoulders are embedded inside the body. The forearm is made of extended and fused metacarpals. The hand is made of phalanges.

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Your lizard has a thoracic kyphosis.

kyphosis

kyphosis

https://www.chortho.com/specialties/kyphosis

The shoulders are in the same place as normal. Because the spine curves back it seems like the shoulders are too far forward. Really the back is farther back. The spine is curved and so the front to back (anterior - posterior) excursion of the thorax is greater.

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