This is a very nice critter, I thought they were gonna be bigger.
So they have heat pits, I'm curious of the structure of these, though the detail may not be entirely necessary I am always curious about more and more elaboration.
https://en.m.wikipedia.org/wiki/Infrared_sensing_in_snakesIt brings back the thought about the visual experience of the sauceback lineage, of which they don't have one. Disgustedorite had chittered at me about my own Saucebacks as one of the first things we discussed together, and I had a similar reaction; whatever stimulus these organs relay probably go to their echolocation brain center (or maybe scent center, but less likely) where it would be translated, there wouldn't all at once be a visual center popping up in the brain. That would probably have to occur in the next descendent if it's even necessary to differentiate between the two. I don't think it would be, otherwise snakes would have distinguished it I think.
The conscious mind inside would probably find it more useful as an addition to their current understanding of the world rather than a brand new experience. Though if it weren't part of the echolocation center it could be just a "gut feeling" for them rather than such an extreme conscious experience like vision for us. It could be like blind sight.
I find the rail system curious. It's slightly difficult for me to understand, but it sounds like the top of the femur has multiple sockets it can rest in, like a racheting thing. This makes me wonder about joint cushioning, do Saucebacks have cartilage between their bones.
I personally think a simplified diagram of the femur shifting would help, though the description works okay.
I like how cooperative and caring they are with one another.