Colonial Spanish Horse
The Colonial Spanish Horse is a foundation type of horse descended from the original Iberian horse stock brought from Spain to the Americas. The ancient form of the breed was once called the Jennet or Spanish Barb. The term encompasses many strains or breeds now found primarily in North America. Its extinction status is considered critical and the horses are registered by several authorities.
The most direct descendant today is possibly the Spanish Mustang. Though the original Mustang descended from the Colonial Spanish horse, not all feral horses of the Americas today are of Colonial Spanish descent, as there has been considerable crossbreeding in some areas.
Modern breeds and types
There is a wide array of horses considered to be near-pure descendants of original Spanish stock, with a variety of names. Some of these include the following modern breeds or breed substrains:
- Iberian Sulphur Horse
- Mustang substrains considered to be Colonial Spanish:
- Gila Bend Mustang
- Pryor Mountain Mustang
- Wilbur-Cruce Mission Horse
- Sulphur Mustang/Sulphur Horse
- Iberian Sulphurs
Hardy Oelke, used MtDNA to show Sulphurs have a link to Iberian Sorraia Mustangs. In a different study, in the early spring of 2001 two of the American Sulphur Horse Association's Board members were contacted by world renown and respected scientists Dr.E.Gus Cothran of the Univ.of Kentucky Equine Research Dept.(now at Texas A&M), and Professor Maria Mar D'Oom of Univ of Lisbon, Portugal, to help them in a joint genetic research project studying Iberian breed horses.
The study was looking into the relationship (if any) between the Iberian (Spanish and Portuguese) breeds. As the Sulphurs are a recognized Iberian breed (Old World blood) now found in the New World they were included in this study. Sulphurs were tested and found to carry the Iberian/Barb 1 Sul mtDNA pattern. As mtDNA is passed in the maternal lines all dams, grand-dams, sisters, female siblings and daughters to these horses will also have the same patterns. 
- Sulphur Mustangs