Are cats evolving opposable thumbs??? (More pictures here)
Probably not. Polydactyly is a condition where extra fingers and/or toes develop in animals. Sometimes they are fully formed, sometimes they just form a small under-developed finger-like lump. Usually there is a genetic defect that causes the extra digits, but it has been associated with the mother taking some types of medications at particular points during pregnancy.
Polydactyly can occur in many species, and is sometimes associated with other abnormalities such as limb deformities and heart problems. It may cause no problem at all, and can assist with mental arithmetic.