Originally Posted by
1Sika
"A dewclaw (commonly referred to as a Dog's thumb) is a vestigial digit on the foot of many mammals, birds, and reptiles (including some extinct orders, like certain theropods). It commonly grows high on the leg so that in digitigrade species, when the animal is standing, it does not make contact with the ground. It can become caught on undergrowth and infection can set in. Dewclaws are perhaps best known in dogs, and they are often removed in young puppies, though there is debate on whether this is necessary."
An answer I found on the net. Should hopefully not open to much of a massive debate.