Probably this is question is related with things like snakes recovering their limbs or an anatomically correct naga or lamia or medusa. But now I am thinking other possible form of "snake limbs", the idea arose that snakes could obtain small limbs with those of an arthropod or specifically a centipede from their ribs.
But that was some ridiculous why a snake would need a lot of little legs that will not make the difference between its normal locomotion, so my conclusion was that this new limbs probably just could be useful at specific zones of the body, neither I am sure about the real uses but I have some disperse ideas, for that reason I made a fast drawing:
A cobra hood with arthropod-like limbs, looks some like the facehugger from alien, so I thought that probably could be used to grab on to some unsuspecting prey and feed in larger quantities for days by depleting the prey like a monitor. Other option, maybe being a giant arm (compared with the size), or less possible eventually developing multiple amrs like some representation of a naga.
But the showed examples shows the cobra's hood anatomy like a pair of ribs for any vertebrae, with multiple joints and with necesary muscles to make the hood move to behind the head and what I found is not currently possible.
Then my principal point is, is it really possible that new joints come from the ribs developing segmented ribs (related with how animals get new joints)?
Could really work this type of limbs?
Finally I would ask about if this can become to more humanoid arms, at least able to manipulate objects, but I thought this is excesive, they do not have the required structures, shoulder blade, collar bone and breastbone