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Description
The Caudofemoralis muscles attach the femur to the tail in tetropods. In dinosaurs such as this T. rex, the C. longus muscle extends quite far down the tail, and plays a major role in powering their locomotion. In most dinosaur animation (WWD, JP), the dinosaur’s tail swings in a passive, intuitive way corresponding with the shift of the animal’s body as it walks (i.e. right when the right leg steps forward and shifts the body in that direction as in diagram 2a.).
However, muscles contract when used, and there are a lot of muscles involved here. With this in mind, as the muscles contract when the leg moves back, should the tail instead shift left when the right leg steps forward and the left leg moves back, since the contraction of those muscles is powering the animal’s movement? This makes the tail movement active and goes against the passive shift in weight. With that in mind 2b. makes the most sense to me. In looking at Saurian animation it seems like they animate closer to 2b., and given the rigor with which they make their models, it makes me all the more confident. If this is the case, that will change how I position the tail in my paleoart, which was previously closer to 2a.
Another thought that crossed my mind is perhaps 2a. is the direction when walking and 2b. when running as faster movement would contract the muscles with more force?
I would love to hear your thoughts.
Cheers, folks!

Description
The Caudofemoralis muscles attach the femur to the tail in tetropods. In dinosaurs such as this T. rex, the C. longus muscle extends quite far down the tail, and plays a major role in powering their locomotion. In most dinosaur animation (WWD, JP), the dinosaur’s tail swings in a passive, intuitive way corresponding with the shift of the animal’s body as it walks (i.e. right when the right leg steps forward and shifts the body in that direction as in diagram 2a.).
However, muscles contract when used, and there are a lot of muscles involved here. With this in mind, as the muscles contract when the leg moves back, should the tail instead shift left when the right leg steps forward and the left leg moves back, since the contraction of those muscles is powering the animal’s movement? This makes the tail movement active and goes against the passive shift in weight. With that in mind 2b. makes the most sense to me. In looking at Saurian animation it seems like they animate closer to 2b., and given the rigor with which they make their models, it makes me all the more confident. If this is the case, that will change how I position the tail in my paleoart, which was previously closer to 2a.
Another thought that crossed my mind is perhaps 2a. is the direction when walking and 2b. when running as faster movement would contract the muscles with more force?
I would love to hear your thoughts.
Cheers, folks!