I have a 7 weeks old smooth coat st bernard...she has all charateristics but she is very lean from legs and neck moreover her head is small bit wrinkeled.is she purebred.

It good be just a fluke, but I'm not really sure. Is there a reason she needs to be? I have a purebred Aussie and a pitbull/boston terrier mix and both are really great dogs. They both have their quirks, the mixed is a shy one and the Aussie has seizures. Dogs are awesome no matter what their bloodline, same with everything else in the world.