Until very recently, it was official US government policy to more or less forcibly transform Native American warriors into farmers. US government agents made sure that Indian pony stallions were either castrated or slaughtered. Heavy horses bred for harness were brought in to cross on the local mares.
Harness horses or trotters, whether heavy draft horses like Clydesdales or fast flashy carriage horses like the Standardbred have obtuse or open angles of 100-110o at the hip and shoulder. Open angles at the hip and shoulder joints does show if there has been any significant trotter influence in a horse’s ancestors. Even if the founding sires were hot-blooded rectangular Turkomen gallopers, two hundred years on most Thoroughbreds still show the more open angled bone structure of the cold-blood mares they descend from.
Baroque horse breeders and trainers did not consider harness horses or trotters suitable for riding. Those open angles make for straight shoulders, short necks, sloping rumps and rough choppy gaits that are still considered faults in a riding horse. Since Baroque warhorses were never intended to pull a plow, Spanish Colonial’s used mules, donkeys and oxen as beasts of burden.
So one of the quickest least invasive ways to check whether or not a herd thought to be Spanish Colonial horses has significant amount of trotters in their ancestry is to check the biomechanics of their hip and shoulder joints. I would love to have full catalogue of side views of the horses running on Pueblo and public lands between Espanola and Albuquerque. But, side view conformation shots are neither glamorous or easy to take.

Getting an undistorted side view is a challenge even if the photographer has a handler and a patient horse. But even with slight distortion, this stallion from the Placitas herd clearly has 90o angles front and back. That means that there is no significant amount of trotter blood in his ancestry.
However, you can see that his balance is naturally inclined slightly to the front by the slope of the red line running through his shoulder and hip joints. The blue rectangle shows also shows that he is actually a just bit more of a rectangular horse or a galloper than a square horse. Chances are his ancestors were selected for their speed as much as their agility, much like the Choctaw Princess. Here she is illustrating the very same geometry on a very skinny frame.

Since free-roaming horses normally travel twenty to twenty-five miles day, this Placitas stallion may show the same biomechanics as the Choctaw Princess does because they share the same bloodlines. Gilbert Jones of the Southwest Spanish Mustang registry lived in Tijeras and ran his Spanish Colonial horses on the open land between the Manzano Mountains and Cerrillos just south west of Pueblo lands in the 1950’s. This is the kind of relationship DNA testing can illuminate.
Genuinely square and rectangular horses both have 90o angles at the hip and shoulder joints, but the square horse has a little more slope to their pelvis and upper arm. Unfortunately, I do not have a recent photo of a truly square horse from this area of New Mexico. However, a combination of enthusiasm, generosity and fragmentation among Spanish Colonial horse fanciers over the last fifty years has resulted in scattered, often poorly documented, populations of Spanish Colonial horses on Indian and private lands, especially in the Dakotas.

I decided to use this Spanish Colonial free roaming stallion below as an example of a square horse. Again, there is some slight distortion due to the perspective of the photo, but the right angles at the shoulder and hip are clear. This stallion is actually built like the scale that Baroque horse trainers and 19th century cavalry manuals idealized. His fore hand and hindquarters are balanced, as you can see by the horizontal line drawn though them.
As it turns out, the quintessential square horse prized by Baroque trainers is actually a biomechanical diamond. If I was any good at bureaucracy, I would start a Square Horse Certification program and document these living examples of the balance and bone structure that has allowed these horses and their humans to perform unequaled feats of fantasy and endurance for millennia. Square and rectangular horses are rare jewels that we should prize now as much as horsemen did in the past.
But I am a lousy bureaucrat. What I can do is urge people to learn to look at how their horses are put together and appreciate both their historical and the equestrian value. You can find more on genuinely square horses, rectangular gallopers and trotters in my book The Gymnastic Circle.
For more posts on equine bio-mechanics click here