Staff at Mac's Mission, an animal rescue center in Missouri, named him Narwhal. The healthy 10-week-old pup has an extra tail, smack in the middle of his forehead.
Rochelle Steffen, who runs Mac's Mission, named after a pit-bull terrier she rescued seven and a half years ago, told BBC News Narwhal "is in no pain and plays for hours". … And X-rays had showed his secondary tail, about a third the size of his actual tail, was not connected to anything and served no purpose other than to make him the "coolest puppy ever".
Narwhal will not be made available for adoption until he's grown up some, to confirm the secondary tail is healthy.