That Colonial Spanish Atlas Bone

When I finally found a lunging cavesson that came close to meeting my criteria for humane head gear, it came with an ‘ergonomically’ designed head stall. I wanted the cheek strap that prevented the head stall from sliding into the horse’s eyes and the padded noseband without chains, cables, or metal plates inserted. It wasn’t until I was putting the headstall on my Colonial Spanish stallion Asad that I realized I had a problem.

When I put the ergonomically designed headstall I had purchased on his head, it made him uncomfortable. His ears are set so far apart that the ends of the curves designed to accommodate the base of his ears press into them instead. It was a problem I had run into before.

After I sent measurements of my Colonial Spanish horses to the Albuquerque Museum so they could get their model-maker based at the Kentucky Horse Park to fabricate something that would fit their set of 15th century Spanish Horse armor, the armor fit perfectly, except for the chevron or face piece. It seems that Colonial Spanish horses have their ears set low and wide apart, and the model maker had placed the ears high and close together. The characteristic broad forehead and wideset ears still breed true because there are visible anatomical differences in the atlas bones of Colonial Spanish horses.

When Sharon May-Davis ‘The Bone Lady’ viewed a number of skeletons from Vickie Ives’ Colonial Spanish (Mustang) graveyard in the early 2000’s, she noted the shape of their Atlas vertebra, the first cervical vertebra behind the skull or C1, differed from those of other breeds. She had not encountered this pear like shape of the first cervical vertebra before.

Eventually, she found a similar variations in other Colonial Spanish strains, including the now-extinct Abaco Island horses. Some strains of miniature horses share the trait and the Argentinian Falabela are also descended from Colonial Spanish horses found in Argentina, which might explain the similarity.

Sharon May-Davis noted that the Wing of Atlas, also known as the transverse process of C1, appears in most breeds as a semi-circular lateral downward facing extension from the vertebral body.

From Sharon May-Davis

In the Colonial Spanish horse, the wing of the atlas starts at the same place as other horses, from the upper edge of the jugular groove, but instead of traveling upwards towards the ear it deviates dorsally towards the nuchal ligament, centered under the mane. To palpate the Atlas in the Colonial Spanish horse, run your thumb or forefinger along its wing and note its sharp upward angulation.

Other aspects of the Colonial Spanish cervical vertebrae Sharon May-Davis found to be of note were the dorsal area caudal to the Alar region, the spinal foramen, the actual shape of the wing from convex to concave and the articulating surface of C1 that receives the dens from the Axis (C2).

Atlas and axis vertebrae of a modern horse
from Rod Nikkels’ blog

The Atlas and Axis are two very unique vertebrae that define the range of motion of a horse’s head. Such a distinctive and consistent variation in their shape must also be consistently reflected in the horse’s movement. And indeed, the elevated head and neck and the vertical profile so greatly prized in upper level dressage is based on the illustrations of Baroque horses of Iberian and barb descent.

Capt Beudant on Robertsart II,
A 1913 French Remount in North Africa

So it is not so much a matter of what Colonial Spanish horses can do because of their anatomical differences, it is a matter of what other types of horses can NOT do. Modern sport horses suffer greatly from their rider’s attempts to force their head and necks into what are anatomically impossible frames for them. Their horses develop arthritis, cranial nerve damage that leads to head-shaking and other behavioral problems, problems with their breathing all the way up to the extreme of crushing of their tracheal cartilage and more I can’t bring myself to think of.

Breeding to retain the distinctly Colonial Spanish trait of wide set ears on a broad flat poll is also breeding to retain the distinctive movements of the Colonial Spanish horse. It also makes the Colonial Spanish influence a valuable asset in any sport-horse or sport-pony breeding program that wants to reduce the suffering of their performance mounts. Breeding for horses that are anatomically capable of performing as their rider’s demand is fundamental to any humane modality of competition.

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