In the TOS film Star Trek III: The Search for Spock, Klingon captain Kruge has a vicious looking lizard-dog at his side. The animal is never given a name, although it was called "monster dog" behind the scenes. It's obviously not a targ but later in the sixth movie, we see similar animals - this time covered in white fur - on the Klingon planet of Rure Penthe, which are identified in canon as a type of Klingon Jackal. There are obvious differences between the two, but certainly no more difference that that between a Pitbull and a Great Dane.
Within canon, is Kruge's pet intended to be a breed of Klingon Jackal, as seen on-screen in Star Trek VI: The Undiscovered Country, and mentioned a couple times on Deep Space Nine?