Chapman, VA; Zeiner, FN: The anatomy of polydactylism in cats with observations on genetic control Anatomical Record 141:205 - 217, 1961 (messybeast.com)
For example, the Maine Coon cat commonly has extra toes, a completely harmless condition known as polydactylism. (blog.pawedin.com)
These kitties are born with an abnormal, dominant genetic mutation called polydactylism. (floridawildvethospital.com)