Hey this is pretty cool.
I can't upload images currently unfortunately as there seems to be a forum issue.
Here's some observations for you anyway, just my 2c
I think the silhouettes could use a little tweaking. The brachiocephalicus for instance, might benefit from pulling straighter when the front limbs are stretched forward.
Also the brachioradialis, when the front limbs are bent. Have a look at this:
The neck muscles are vibrating quite a lot
I can't find any evidence for a muscle that exists between the hind limbs and the rib cage. Many muscle models have this for some reason. I think we even had it on the lion at one point but removed it in favour of doing this area completely at the fat/skin level.
The deformation of the ribs seems to be a little non-uniform going from stretch to compression.
Think the animation could use another pass to help it feel more natural.
Hope that helps!
Happy new year.