WITHOUT raising the ire of the Mountain horse people who (I believe) are going through the same type of argument that the Appalousa people were in the 1990's (about what a REAL MH or Appalousa is,) I can tell you that the numbers of Mountain horses were low and breeders were outcrossing with other stock. I DO know that TWH's were bred from many breeds including Mountain Horses, and the gaits are very similar, hence it makes sense to introduce TWH genetics into MH's. I'm getting closer and closer to my gelding, after a "rocky" (pun) start, but my mare typifies the breed standard, Despite that fact that she has two "unknown" parents listed in her paperwork.
"Warren's Cindy" Her Back side and long tail
Her Granddam, "Jason's Lady Ann" has unregistered parentage. BUT, I can tell you that she NEVER trots under saddle and is extremely smooth, much more so than my gelding, "Long Arm of the Law,"
And much smoother than any TWH or TWH cross I've ever owned or ridden, so, it kinda makes you wonder.
See, he looks like a TWH in EVERY picture we take of him.
(I'm brave posting this picture, but I've lost 35 lbs since this was taken.)
The Mountain Horses gait with smaller steps and move a little more like a Peruvian Paso, imo. Whereas TWH's eat up the ground and move a little more like a show GS, with a dropped hind end.
Now, "Merry Boy's Hart, (1984-2008, RIP), was a TWH and looked, rode and acted like one.~
...and, or TWH/QH cross, "Tyke (1970-2998, RIP) might as well have been a full-blooded TWH, too.~
Just thought I'd share. =D