...developed or paralazed. Is this possible? The litter is 9 days old. mom dogs is treating the puppies all the same. The puppy can move and makes it to mom to eat fine.
Yes, very possible. A deformity possibly from in the womb or maybe a wound suffered at birth or after birth. Possible outcome is the leg will need amputating. Take the pup to the vet immediately before infection/gangrene settles in if you want to keep the pup alive.
Yes, unfortunately it is possible. But the pup may have suffered some sort of trauma in the nest - did mum overlay him, for example? Get it to your vet because you will need to assess his ongoing quality of life, and make a decision about him. It's sad, but this is why dogs have multiples (and other animals of course) - and only the strongest survive in the wild after all.